General Description
The MAX3380E/MAX3381E are +2.35V to +5.5V-pow-
ered EIA/TIA-232 and V.28/V.24 communication inter-
faces with low power requirements, high data-rate
capabilities, and enhanced electrostatic discharge
(ESD) protection on both the TTL and RS-232 sides.
The MAX3380E/MAX3381E have two receivers and two
transmitters. All RS-232 inputs, outputs, and logic input
pins are protected to ±15kV using IEC 1000-4-2 Air-
Gap Discharge method and the Human Body Model,
and ±8kV using IEC 1000-4-2 Contact Discharge
method.
The proprietary low-dropout transmitter output stage
enables true RS-232 performance from a +3.1V to
+5.5V supply with a dual charge pump. The parts
reduce the transmitter output levels to RS-232-compati-
ble levels with no increase in supply current for sup-
plies less than +3.1V and greater than +2.35V. The
+2.35V to +5.5V operating range is fully compatible
with lithium-ion (Li+) batteries. The charge pump
requires only four small 0.1µF capacitors for operation.
The MAX3380E/MAX3381E transceivers use Maxim’s
revolutionary AutoShutdown Plus™ feature to auto-
matically enter a 1µA shutdown mode. These
devices shut down the on-board power supply and
drivers when they do not sense a valid signal transi-
tion for 30 seconds on either the receiver or trans-
mitter inputs.
The MAX3380E is capable of transmitting data at
rates of 460kbps while maintaining RS-232 output
levels, and the MAX3381E operates at data rates up
to 250kbps. The MAX3381E offers a slower slew rate
for applications where noise and EMI are issues. The
MAX3380E/MAX3381E have a unique VLpin that
allows interoperation in mixed-logic voltage systems
down to +1.65V. Both input and output logic levels
are referenced to the VLpin. The MAX3380E/MAX3381E
are available in a space-saving TSSOP package.
Applications
Cell Phone Data Lump Cables
PDA Data Lump Cables
GPS Receivers
Digital Cameras
Features
♦±15kV ESD Protection on All CMOS and RS-232
Inputs and Outputs (Except INVALID)
±15kV Human Body Model
±15kV IEC 1000-4-2 Air-Gap Discharge
±8kV IEC 1000-4-2 Contact Discharge
♦Operates Over Entire Li+ Battery Range
♦Low Logic Threshold Down to +1.65V for
Compatibility with Cell Phone Logic Supply Voltages
♦1µA Low-Power AutoShutdown Plus Mode
♦Compatible with Next-Generation GSM Data Rates
♦20-Pin TSSOP Package
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
________________________________________________________________ Maxim Integrated Products 1
19-2128; Rev 0; 8/01
Ordering Information
PART TEMP. RANGE
PIN-PACKAGE
MAX3380ECUP
0°C to +70°C
20 TSSOP
MAX3380EEUP
-40°C to +85°C
20 TSSOP
MAX3381ECUP
0°C to +70°C
20 TSSOP
MAX3381EEUP
-40°C to +85°C
20 TSSOP
Pin Configuration appears at end of data sheet.
MAX3380E/
MAX3381E
R2OUT
R1OUT
R2IN
GND
RS-232
OUTPUTS
TTL/CMOS
INPUTS T2IN
T1IN
C2-
C2+
C1-
C1+
R1IN
T2OUT
T1OUT
V-
V+
VCC VL
C1
0.1μF
C2
0.1μF
C5
0.1μF
+3.3V
RS-232
INPUTS
TTL/CMOS
OUTPUTS
5kΩ
5kΩ
C3
0.1μF
C4
0.1μF
VL
VL
FORCEON
FORCEOFF
Typical Operating Circuit
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
AutoShutdown Plus is a trademark of Maxim Integrated Products
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = +2.35V to +5.5V, VL= +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥+4.5V, C1 = 0.047µF,
C2 = C3 = C4 = 0.33µF; TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL= +3.3V, TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Note 1: V+ and V- can have maximum magnitudes of +7V, but their absolute difference cannot exceed +13V.
VCC to GND...........................................................-0.3V to +6.0V
VLto GND..............................................................-0.3V to +6.0V
V+ to GND .............................................................-0.3V to +7.0V
V- to GND ..............................................................+0.3V to -7.0V
V+ + |V-| (Note 1) .................................................................+13V
Input Voltages
T_IN, FORCEON, FORCEOFF to GND ...............-0.3V to +6.0V
R_IN to GND .....................................................................±25V
Output Voltages
T_OUT to GND...............................................................±13.2V
R_OUT, INVALID to GND...........................-0.3V to (VL+ 0.3V)
Short-Circuit Duration T_OUT to GND........................Continuous
Continuous Power Dissipation (TA= +70°C)
20-Pin TSSOP (derate 10.9mW/°C over +70°C) .........879mW
Operating Temperature Ranges
MAX3380ECUP/MAX3381ECUP........................0°C to +70°C
MAX3380EEUP/MAX3381EEUP .....................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Receivers idle, VT_IN = VCC or GND,
FORCEON = GND, FORCEOFF = VCC 10
Supply Current, AutoShutdown
Plus ICC
FORCEOFF = GND 1 10
µA
Supply Current, Normal Operation
ICC FORCEON = FORCEOFF = VL, no load 0.3 1
mA
LOGIC INPUTS (T_IN, FORCEON, FORCEOFF)
VCC = +5.5V, VL = +5.5V 0.4 1.2
Input Logic Threshold Low VIL VCC = +2.5V, VL = +1.65V 0.4 V
VCC = +5.5V, VL = +5.5V
VL ✕ 0.66
Input Logic Threshold High VIH VCC = +2.5V, VL = +1.65V
VL ✕ 0.66
V
Transmitter Input Hysteresis 0.5 V
Input Leakage Current
±0.01
±1µA
RECEIVER OUTPUTS (R_OUT) AND INVALID
Output Voltage Low IOUT = 500µA 0.5 V
Output Voltage High IOUT = -500µA
VL - 0.4 VL - 0.2
V
RECEIVER INPUTS (R_IN)
Input Voltage Range -25
+25
V
VL = +3.3V 0.6 1.2
Input Threshold Low TA = +25°CVL = +5.0V 0.8 1.5 V
VL = +3.3V 1.5 2.4
Input Threshold High TA = +25°CVL = +5.0V 1.8 2.4 V
Input Hysteresis 0.3 V
Input Resistance TA = +25°C 3 5 7 kΩ
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
_______________________________________________________________________________________ 3
PARAMETER
SYMBOL
CONDITIONS MIN
TYP MAX
UNITS
AutoShutdown Plus (FORCEON = GND, FORCEOFF = VL)
Positive threshold 2.7
Receiver Input Threshold to
INVALID Output High Figure 3 Negative threshold
-2.7
V
Receiver Input Threshold to
INVALID Output Low Figure 3
-0.3
0.3 V
Receiver Positive or Negative
Threshold to INVALID High tINVL VCC = +5.0V, Figure 4 0.3 µs
Receiver Positive or Negative
Threshold to INVALID Low tINVH VCC = +5.0V, Figure 4 30 µs
Receiver or Transmitter Edge to
Transmitters Enabled tWU VCC = +5.0V, Figure 4 15 µs
Receiver or Transmitter Edge to
Transmitters Shutdown
tAU T OS H D N
VCC = +5.0V, Figure 4 30 s
TRANSMITTER OUTPUTS
VCC Mode Switch Point
(VCC Falling) T_OUT = ±5.0V to ±3.7V
2.95
3.1
3.25
V
VCC Mode Switch Point
(VCC Rising) T_OUT = ±3.7V to ±5.5V 3.3 3.5 3.7 V
VCC Mode Switch Point
Hysteresis
400
mV
V
C C
= + 3.25V to + 5.5V ,
V
C C
fal l i ng ±5
±5.4
Output Voltage Swing
All transmitter
outputs loaded
with 3kΩ to ground
V
C C
= + 2.5V to + 2.95V ,
V
C C
fal l i ng
±3.7
V
Output Resistance VCC = 0, transmitter output = ±2.0V
300 10M
Ω
Output Short-Circuit Current ±60
mA
Output Leakage Current VOUT = ±12V, transmitters disabled ±25 µA
ESD PROTECTION
Human Body Model
±15
IEC 1000-4-2 Air-Gap Discharge Method
±15
R_IN, T_OUT, R_OUT, T_IN,
FORCEON, FORCEOFF
IEC 1000-4-2 Contact Discharge Method ±8
kV
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +2.35V to +5.5V, VL= +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥+4.5V, C1 = 0.047µF,
C2 = C3 = C4 = 0.33µF; TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL= +3.3V, TA= +25°C.)
-6
-2
-4
2
0
6
4
8
0 1000 1500500 2000 2500 3000
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3380E toc01
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
VOUT+
VOUT-
VCC = +4.2V
-6
-2
-4
2
0
6
4
8
0 1000 1500500 2000 2500 3000
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3380E toc02
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
VOUT+
VOUT-
VCC = +2.5V
0
5
10
15
20
25
30
35
40
0 1000500 1500 2000 2500 3000
MAX3380E
SLEW RATE vs. LOAD CAPACITANCE
MAX3380E toc03
LOAD CAPACITANCE (pF)
SLEW RATE (V/μs)
VCC = +4.2V
VCC = +2.5V
Typical Operating Characteristics
(VCC = VL= +4.2V, C1 = 0.22µF, C2 = C3 = C4 = 1µF, C5 = 0.1µF parallel with 47µF, RL= 3kΩ, CL= 1000pF, data rate is 250kbps,
TA= +25°C, unless otherwise noted.)
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
4 _______________________________________________________________________________________
TIMING CHARACTERISTICS
(VCC = +2.35V to +5.5V, VL= +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥+4.5V, C1 = 0.047µF,
C2 = C3 = C4 = 0.33µF; TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL= +3.3V, TA= +25°C.)
PARAMETER
SYMBOL
CONDITIONS MIN
TYP MAX
UNITS
MAX3381E 250
Maximum Data Rate RL = 3kΩ, CL = 1000pF, one
transmitter switching MAX3380E 460
kbps
tPLH
0.15
Receiver Propagation Delay tPHL
Receiver input to receiver output, CL = 100pF 0.15
µs
Transmitter Skew
⏐tPHL- tPLH⏐
(Note 2)
200
ns
Receiver Skew
⏐tPHL- tPLH⏐
50 ns
Transition Region Slew Rate
(MAX3380E)
VCC = +4.2V, -3.0V < T_OUT< +3.0V,
RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C
20
100
V/µs
Transition Region Slew Rate
(MAX3381E)
VCC = +4.2V, -3.0V < T_OUT< +3.0V,
RL = 3kΩ, CL = 150pF to 1000pF, TA = +25°C
630
V/µs
Transition Region Slew Rate
(MAX3380E)
VCC = +2.35V, -3.0V < T_OUT< +3.0V,
RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C
30
V/µs
Transition Region Slew Rate
(MAX3381E)
VCC = +2.35V, -3.0V < T_OUT< +3.0V,
RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C
10
V/µs
Note 2: Transmitter skew is measured at the transmitter zero crosspoint.
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
_______________________________________________________________________________________ 5
6
7
8
9
10
11
12
13
14
0 1000500 1500 2000 2500 3000
MAX3381E
SLEW RATE vs. LOAD CAPACITANCE
MAX3380E toc04
LOAD CAPACITANCE (pF)
SLEW RATE (V/μs)
VCC = +4.2V
VCC = +2.5V
0
10
20
30
40
50
60
70
80
0 1000500 1500 2000 2500 3000
SUPPLY CURRENT vs. LOAD CAPACITANCE
WHEN TRANSMITTING DATA
MAX3381E toc05
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
460kbps
250kbps
20kbps
1 TRANSMITTER SWITCHING
-6
-2
-4
2
0
6
4
8
TRANSMITTER OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE (VCC FALLING)
MAX3380E toc06
SUPPLY VOLTAGE (V)
TRANSMITTER OUTPUT VOLTAGE (V)
2.5 3.5 4.5 5.5
VOUT+
VOUT-
-6
-2
-4
2
0
6
4
8
TRANSMITTER OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE (VCC RISING)
MAX3380E toc07
SUPPLY VOLTAGE (V)
TRANSMITTER OUTPUT VOLTAGE (V)
2.5 3.5 4.5 5.5
VOUT+
VOUT-
0
5
10
15
20
25
2.5 3.5 4.5 5.5
SUPPLY CURRENT
vs. SUPPLY VOLTAGE (VCC FALLING)
MAX3380E toc08
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
1 TRANSMITTER SWITCHING
1μs/div
T_IN
5V/div
T_OUT
5V/div
MAX3380E toc09
MAX3380E
DATASTREAM VCC = +4.2V
5V
0
5V
0
-5V
VCC = VL = +2.5V
1μs/div
T_IN
5V/div
T_OUT
5V/div
MAX3380E toc10
MAX3380E
DATASTREAM VCC = +2.5V
5V
0
5V
0
-5V
Typical Operating Characteristics (continued)
(VCC = VL= +4.2V, C1 = 0.22µF, C2 = C3 = C4 = 1µF, C5 = 0.1µF parallel with 47µF, RL= 3kΩ, CL= 1000pF, data rate is 250kbps,
TA= +25°C, unless otherwise noted.)
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
6 _______________________________________________________________________________________
Detailed Description
The MAX3380E/MAX3381E are RS-232 transceivers that
maximize battery life by reducing current consumption
at low battery levels. When the supply voltage is above
+3.7V, the RS-232 outputs are at ±5.5V, which is com-
pliant with the RS-232 standard. As the supply voltage
drops below the +3.1V set point, the RS-232 outputs
change to ±3.7V, which is compatible with the RS-232
standard. The outputs will remain at the compatible lev-
els until the supply voltage rises above +3.5V, where
they return to compliant levels. 400mV of hysteresis pro-
tects against power-supply bounce that may cause
numerous mode changes.
Most devices that use charge pumps to double and
invert voltages consume higher current when the supply
voltage is less than half of the required output voltage.
This is due to the fact that the charge pump is constant-
ly operating because the output voltage is below the
regulation voltage. This requires more supply current
because the output will never reach the regulation volt-
age and switch off. The MAX3380E/MAX3381E reduce
the output voltage requirement allowing the charge
pump to operate with supply voltages down to +2.35V.
Dual-Mode Regulated Charge-Pump
Voltage Converter
The MAX3380E/MAX3381Es’ internal power supply is a
dual-mode regulated charge pump. The output regula-
tion point depends on VCC and the direction in which
VCC moves through the switchover region of +2.95V <
VCC < +3.7V.
For supply voltages above +3.7V, the charge pump will
generate +5.5V at V+ and -5.5V at V-. The charge
pumps operate in a discontinuous mode. If the output
voltages are less than ±5.5V, the charge pumps are
enabled; if the output voltages exceed ±5.5V, the
charge pumps are disabled.
For supply voltages below +2.95V, the charge pump
will generate +4.0V at V+ and -4.0V at V-. The charge
pumps operate in a discontinuous mode.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies (see Typical Operating Circuit).
Pin Description
PIN NAME FUNCTION ESD
PROTECTED
1 C1+ Positive Terminal of Voltage-Doubler Charge-Pump Capacitor —
2 V+ +5.5V/+4.0V Generated by the Charge Pump —
3 C1- Negative Terminal of Voltage-Doubler Charge-Pump Capacitor —
4 C2+ Positive Terminal of Inverting Charge-Pump Capacitor —
5 C2- Negative Terminal of Inverting Charge-Pump Capacitor —
6 V- -5.5V/-4.0V Generated by the Charge Pump —
7
INVALID
INVALID is asserted if any inputs of the receivers are in an invalid state;
-0.3V < VR_IN < +0.3V —
8, 9 T_IN TTL/CMOS Transmitter Inputs Referenced to VL (T1IN, T2IN) ✔
10, 11
R_OUT
TTL/CMOS Receiver Outputs Referenced to VL (R2OUT, R1OUT) ✔
12
FORCEON
Force-On Input. Drive high to override automatic circuitry keeping transmitters on
(FORCEOFF must be high) (Table 1). ✔
13 VLLogic Level Supply. +1.65V to +5.5V, sets CMOS logic thresholds and CMOS
outputs. —
14, 15
R_IN RS-232 Receiver Inputs (R2IN, R1IN) ✔
16, 17
T_OUT RS-232 Transmitter Outputs (T2OUT, T1OUT) ✔
18 GND Ground —
19
FORCEOFF
Force-Off Input. Drive low to shut down transmitters and on-board power supply.
This overrides all automatic circuitry and FORCEON (Table 1). ✔
—
20 VCC +2.35V to +5.5V Supply Voltage
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
_______________________________________________________________________________________ 7
Voltage Generation in the
Switchover Region
The MAX3380E/MAX3381E include a switchover circuit
between RS-232-compliant and RS-232-compatible
modes that has approximately 400mV of hysteresis
around the switchover point. The hysteresis is shown in
Figure 1. This large hysteresis helps to avoid mode
change under battery or power-supply bounce.
Under a decaying VCC, the charge pump will generate
an output voltage of ±5.5V with a VCC input range
between +3.1V and +5.5V. When VCC drops below the
switchover point of +3.1V, the charge pump switches
into RS-232-compatible mode generating ±4V.
When VCC is rising, the charge pump will generate an
output voltage of ±4.0V, while VCC is between +2.5V
and +3.5V. When VCC rises above the switchover volt-
age of +3.5V, the charge pump switches to RS-232-
compliant mode to generate an output voltage of ±5.5V.
RS-232 Transmitters
The transmitters are inverting level translators that con-
vert CMOS-logic levels to RS-232-compatible levels.
The MAX3380E/MAX3381E will automatically reduce
the RS-232-compliant levels from ±5.5V to ±3.7V when
VCC falls below approximately +3.1V. The reduced lev-
els are RS-232-compatible and reduce supply current
requirements that help preserve the battery. Built-in
hysteresis of approximately 400mV for VCC ensures
that the RS-232 output levels do not change if VCC is
noisy or has a sudden current draw causing the supply
voltage to drop slightly. The outputs will return to RS-
232-compliant levels (±5.5V) when VCC rises above
approximately +3.5V.
The MAX3380E/MAX3381E transmitters guarantee a data
rate of 460kbps/250kbps, respectively, with worst-case
loads of 3kΩin parallel with 1000pF. Transmitters can be
paralleled to drive multiple receivers.
When FORCEOFF is driven to ground, the transmitters
are disabled and the outputs go into high impedance;
receivers remain active. When the AutoShutdown Plus
circuitry senses that all receiver and transmitter inputs
are inactive for more than 30s, the transmitters are dis-
abled and the outputs go into a high-impedance state,
and the receivers remain active. When the power is off,
the MAX3380E/MAX3381E permit the outputs to be dri-
ven up to ±12V.
The transmitter inputs have a 400kΩactive positive
feedback resistor. They will retain a valid logic level if
the driving signal is removed or goes high impedance.
Connect unused transmitter inputs to VCC or ground.
RS-232 Receivers
The receivers convert RS-232 signals to logic levels
referred to VL. Both receivers are active in shutdown
(Table 1).
AutoShutdown Plus Mode
The MAX3380E/MAX3381E achieve a 1µA supply current
with Maxim’s AutoShutdown Plus feature, which operates
when FORCEOFF is high and FORCEON is low. When
these devices do not sense a valid signal transition on
any receiver and transmitter input for 30s, the on-board
charge pumps are shut down, reducing supply current
to 1µA. This occurs if the RS-232 cable is disconnected
or if the connected peripheral transmitters are turned off,
and if the UART driving the transmitter inputs is inactive.
The system turns on again when a valid transition is
applied to any RS-232 receiver or transmitter input. As a
result, the system saves power without changes to the
existing BIOS or operating system.
Figures 2a and 2b show valid and invalid RS-232
receiver voltage levels. INVALID indicates the receiver
input’s condition, and is independent of the FORCEON
and FORCEOFF states. Figure 2 and Table 1 summa-
rize the MAX3380E/MAX3381E’s operating modes.
FORCEON and FORCEOFF override AutoShutdown
Plus circuitry. When neither control is asserted, the IC
selects between these states automatically based on
the last receiver or transmitter input edge received.
By connecting FORCEON to INVALID, the MAX3380E/
MAX3381E is shut down when no valid receiver level and
no receiver or transmitter edge is detected for 30s, and
wakes up when a receiver or transmitter edge is detect-
ed (Figure 2c).
20ms/div
VCC
2V/div
V+
2V/div
+4.5V
+2.5V
+5.8V
+4.4V
Figure 1. V+ Switchover for Changing Vcc
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
8 _______________________________________________________________________________________
+0.3V
-0.3V
INVALID
R_IN
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30μs.
30µs
TIMER
R
+2.7V
-2.7V
INVALID
R_IN
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30μs.
0.3μs
TIMER
R
Figure 2a. I
NVALID
Functional Diagram, I
NVALID
Low Figure 2b. I
NVALID
Functional Diagram, I
NVALID
High
Table 1. AutoShutdown Plus Truth Table
OPERATION
STATUS
FORCEON
FORCEOFF
VALID
RECEIVER
LEVEL
RECEIVER OR
TRANSMITTER EDGE
WITHIN 30s
T_OUT R_OUT
Shutdown
(Forced Off) X 0 X X High-Z Active
Normal Operation
(Forced On) 1 1 X X Active Active
Normal Operation
(AutoShutdown
Plus)
0 1 X Yes Active Active
Shutdown
(AutoShutdown
Plus)
0 1 X No High-Z Active
Normal Operation
INVALID 1 Yes X Active Active
Normal Operation
INVALID 1 X Yes Active Active
Shutdown INVALID 1 No No High-Z Active
Normal Operation
(AutoShutdown) INVALID INVALID Yes X Active Active
Shutdown
(AutoShutdown) INVALID INVALID No X High-Z Active
X = Don’t care
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
_______________________________________________________________________________________ 9
By connecting FORCEON and FORCEOFF to INVALID,
the MAX3380E/MAX3381E are shut down when no valid
receiver level is detected.
VLLogic Supply Input
Unlike other RS-232 interface devices where the receiv-
er outputs swing between 0 and VCC, the MAX3380E/
MAX3381E feature a separate logic supply input (VL)
that sets VOH for the receiver and INVALID outputs. VL
also sets the threshold for the transmitter inputs,
FORCEON and FORCEOFF. This feature allows a great
deal of flexibility in interfacing to many different types of
systems with different logic levels. Connect this input to
+2.7V
+0.3V
0
-0.3V
-2.7V
TRANSMITTERS ENABLED, INVALID HIGH
INDETERMINATE
AutoShutdown, TRANSMITTERS DISABLED,
1μA SUPPLY CURRENT INVALID LOW
INDETERMINATE
TRANSMITTERS ENABLED, INVALID HIGH
POWERDOWN*
AUTOSHDN
FORCEOFF
FORCEON
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 2d. Power-Down Logic
AUTOSHDN
R_IN
T_IN
R
S
30s
TIMER
EDGE
DETECT
EDGE
DETECT
FORCEOFF
FORCEON
Figure 2c. AutoShutdown Plus Logic
VL
0
V+
V-
VCC
0
INVALID
OUTPUT
TRANSMITTER
INPUTS
RECEIVER
INPUTS }INVALID
REGION
TRANSMITTER
OUTPUTS
tAUTOSHDN tWU tWU
tINVL tINVH tAUTOSHDN
Figure 4. AutoShutdown Plus/
INVALID
Timing Diagram
Figure 3. AutoShutdown Trip Levels
MAX3380E/MAX3381E
the host logic supply (+1.65V to +5.5V). The VLinput
will draw a maximum current of 20µA with receiver out-
puts unloaded.
±15kV ESD Protection
Maxim has developed state-of-the-art structures to pro-
tect these pins against an ESD of ±15kV without dam-
age. The ESD structures withstand high ESD in all states:
normal operation, shutdown, and power-down. After an
ESD event, Maxim’s “E” version devices keep working
without latch-up, whereas competing RS-232 products
can latch and must be powered down to remove latch-
up. ESD protection can be tested in various ways. The
transmitter and receiver outputs and receiver and logic
inputs of this product family are characterized for protec-
tion to the following limits:
• ±15kV using the Human Body Model
• ±8kV using the Contact Discharge method speci-
fied in IEC 1000-4-2
• ±15kV using IEC 1000-4-2’s Air-Gap Discharge
method
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
Human Body Model
Figure 5a shows the Human Body Model, and Figure
5b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter-
est, which is then discharged into the test device
through a 1.5kΩresistor.
IEC 1000-4-2
The IEC 1000-4-2 standard covers ESD testing and
performance of finished equipment; it does not specifi-
cally refer to ICs. The MAX3380E/MAX3381E help you
design equipment that meets Level 4, the highest level
of IEC 1000-4-2 without the need for additional ESD-
protection components. The major difference between
tests done using the Human Body Model and IEC
1000-4-2 is higher peak current in IEC 1000-4-2,
because series resistance is lower in the IEC 1000-4-2
model. Hence, the ESD withstand voltages measured
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
10 ______________________________________________________________________________________
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
100pF
RC
1MΩ
RD
1500Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 5a. Human Body ESD Test Model
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
150pF
RC
50MΩ to 100MΩ
RD
330Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 6a. IEC 1000-4-2 ESD Test Model
IP 100%
90%
36.8%
tRL TIME
tDL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
Ir
10%
0
0
AMPERES
Figure 5b. Human Body Current Waveform
100%
90%
60ns
10%
tr = 0.7ns to 1ns
IPEAK
I
30ns t
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
______________________________________________________________________________________ 11
to IEC 1000-4-2 are generally lower than that measured
using the Human Body Model. Figure 6a shows the IEC
1000-4-2 model, and Figure 6b shows the current
waveform for the ±8kV IEC 1000-4-2 Level 4 ESD
Contact Discharge test.
The Air-Gap test involves approaching the device with
a charged probe. The Contact Discharge method con-
nects the probe to the device before the probe is ener-
gized.
Machine Model
The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge resis-
tance. Its objective is to emulate the stress caused by
contact that occurs with handling and assembly during
manufacturing. All pins require this protection during
manufacturing, not just RS-232 inputs and outputs.
Therefore, after PC board assembly, the Machine
Model is less relevant to I/O ports.
Applications Information
Capacitor Selection
The capacitor type used for C1–C4 is not critical for
proper operation. Polarized or nonpolarized capacitors
can be used. The charge pump requires 0.1µF capaci-
tors for +3.3V operation. For other supply voltages, see
Table 2 for required capacitor values. Do not use val-
ues smaller than those listed in Table 2. Increasing the
capacitor values (e.g., by a factor of 2) reduces ripple
on the transmitter outputs and slightly reduces power
consumption. C2, C3, and C4 can be increased without
changing C1’s value. However, do not increase C1
without also increasing the values of C2, C3, C4, and
C5 to maintain the proper ratios (C1 to the other capac-
itors).
When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capaci-
tors with a large nominal value. The capacitor’s equiva-
lent series resistance (ESR) usually rises at low
temperatures and influences the amount of ripple on
V+ and V-.
Power-Supply Decoupling
In most circumstances, connect a 0.1µF capacitor from
VCC to GND. This capacitor is for noise reduction. If the
MAX3380E/MAX3381E are used in a data cable appli-
cation, add a 47µF capacitor from VCC to ground. The
47µF capacitor is used to ensure that the current need-
ed during power-up is supplied to the device. In appli-
cations that are sensitive to power-supply noise,
decouple VCC to ground with a capacitor of the same
value as charge-pump capacitor C1. Connect bypass
capacitors as close to the IC as possible.
Transmitter Outputs when Recovering
from Shutdown
Figure 7 shows two transmitter outputs when exiting
shutdown mode. As they become active, the two trans-
mitter outputs are shown going to opposite RS-232 lev-
els (one transmitter input is high, the other is low). Each
transmitter is loaded with 3kΩin parallel with 1000pF.
The transmitter outputs display no ringing or undesir-
able transients as they come out of shutdown. Note that
the transmitters are enabled only when the magnitude
of V- exceeds approximately 3V.
High Data Rates
The MAX3380E/MAX3381E maintain the RS-232 ±5.0V
minimum transmitter output voltage even at high data
rates. Figure 8 shows a transmitter loopback test cir-
cuit. Figure 9 shows a loopback test result for the
MAX3380E at 460kbps with true RS-232 output voltage
levels (VCC = +4.2V). Figure 10 shows the same test
with RS-232-compatible levels (VCC = +2.5V). With
data rates as high as 460kbps, the MAX3380E is com-
patible with 2.5-Generation GSM standards.
VCC (V) C1, C5 (µF)
C2, C3, C4 (µF)
+2.35 to +3.6 0.1 0.1
+4.5 to +5.5 0.047 0.33
+2.35 to +5.5 0.22 1
Table 2. Minimum Required Capacitor
Values
VCC = 3.3V, C1–C4 = 0.1μF, CLOAD = 1000pF
4μs/div
5V/div
2V/div
T2OUT
T1OUT
FORCEON =
FORCEOFF
5V
6V
6V
0
0
Figure 7. Transmitter Outputs when Recovering from Shutdown
or Powering Up
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
12 ______________________________________________________________________________________
For Figure 9 and Figure 10, a single transmitter was dri-
ven at 460kbps, and all transmitters were loaded with
an RS-232 receiver in parallel with 1000pF.
Data Cable Applications
The MAX3380E/MAX3381Es’ ±15kV ESD protection on
both the RS-232 I/Os as well as the logic I/Os makes
them ideal candidates for data cable applications. A
data cable is both an electrical connection and a level
translator, allowing ultra-miniaturization of cell phones
and other small portable devices.
Previous data cable approaches suffered from com-
plexity due to the required protection circuits on both
the logic side of the cable, as well as on the RS-232
connections. The example shown in Figure 11 shows
the ease of using the MAX3380E/MAX3381E in data
cable applications. For best performance, keep the
logic level lines short and use the RS-232 level lines to
span any distance.
VCC = VL = +2.5V, C1 = 0.1μF, C2 = C3 = C4 = 1μF,
CLOAD = 1000pF
TIME (1μs/div)
T1IN
2V/div
T1OUT
5V/div
R1OUT
2V/div
0
5V
0
-5V
2V
0
2V
Figure 10. Loopback Test Results at 460kbps (VCC = +2.5V)
VCC = VL = +4.2V, C1 = 0.1μF, C2 = C3 = C4 = 1μF,
CLOAD = 1000pF
1μs/div
T1IN
5V/div
T1OUT
5V/div
R1OUT
5V/div
5V
0
5V
0
-5V
5V
0
Figure 9. Loopback Test Results at 460kbps (VCC = +4.2V)
MAX3380E
MAX3381E
5kΩ
R_ IN
R_ OUT
C2-
C2+
C1-
C1+
V-
V+
VCC
C4
C3
C1
C2
VCC
FORCEOFF
T_ OUT
T_ IN
GND
VCC
FORCEON 1000pF
C5
VL
Figure 8. Loopback Test Circuit
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
______________________________________________________________________________________ 13
MAX3380E/
MAX3381E
CELL PHONE
LOGIC LEVELS
R2OUT
R1OUT
T2IN
T1IN
C1+
C1-
R2IN
R1IN
T2OUT
T1OUT
V+
VL
VCC
V-
CTS
Rx
RTS
Tx
VBATT
0.1μF
0.1μF
PERIPHERALS
RS-232 LEVELS
RTS I/O
Rx
CTS
Tx
INVALID
FORCEON
FORCEOFF
C2+
C2-
0.1μF
0.1μF
0.1μF47μF
Figure 11. Typical Application Circuit
Chip Information
TRANSISTOR COUNT: 1467
PROCESS: BiCMOS
20
19
18
17
16
15
14
13
1
2
3
4
5
6
7
8
VCC
FORCEOFF
GND
T1OUTC2+
C1-
V+
C1+
TOP VIEW
T2OUT
R1IN
R2IN
VL
T1IN
INVALID
V-
C2-
12
11
9
10
FORCEON
R1OUTR2OUT
T2IN
MAX3380E/
MAX3381E
TSSOP
Pin Configuration
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products is a registered trademark of Maxim Integrated Products.
TSSOP4.40mm.EPS
PACKAGE OUTLINE, TSSOP 4.40mm BODY
21-0066
1
1
I
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
