DS1830AS/T&R - Maxim Integrated

DS1830/A DS183

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FEATURES

§ 5V (DS1830) or 3.3V (DS1830A) power-on

reset

§ Excellent for systems that need power-on

resets in a consistent sequence

§ Asserts resets during power transients

§ Pushbutton reset input for system override

§ Selectable reset timing

§ Reduces need for discrete components

§ Precision temperature-compensated voltage

reference

§ 8-pin DIP, 8-pin SO, or space saving 8-pin

µSOP

§ Operating temperature of -40°C to +85°C

§ Open-drain, active-low inputs

PIN ASSIGNMENT

PIN DESCRIPTION

1 PBRST - Pushbutton Reset Input

2 TD - Time Delay Select Input

3 TOL - VCC Tolerance Select Input

4 GND - Ground

8 VCC - Power Supply

7 RST1 - Reset 1 Output

6 RST2 - Reset 2 Output

5 RST3 - Reset 3 Output

DESCRIPTION

The DS1830 Reset Sequencer monitors the power supply for an in-tolerance condition and the pushbutton

reset input for a manual reset. First a precision temperature-compensated reference and comparator circuit

monitors the status of the power supply and when an out-of-tolerance condition is detected, an internal

power fail signal is generated that forces the reset lines to go to an active state. If the power supply

returns to an in-tolerance condition, RST1 will release followed by RST2 and finally RST3 . Sequencing of

resets allows for systems to power-up in an orderly manner providing superior reliability.

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DS1830/A

Reset Sequence Pushbutton

D1830/A

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OPERATION — POWER MONITOR

The DS1830 provides the functions of detecting out-of-tolerance conditions on a power supply and

warning a processor based system of impending power failure. When VCC is detected as out-of-tolerance

all reset outputs will be forced active. When VCC returns to a valid state, RST1 will remain active for

period of time based on the condition of the TD input. Reset outputs RST2 and RST3 follow RST1 , each

one at the proper delays for the condition of the TD input. All resets will remain in the inactive state

(high) until the next VCC out-of-tolerance condition or pushbutton reset. On power-up all resets are kept

active for an appropriate period determined by the status of the TD input after the power supply inputs

have reached the selected tolerance. This allows the power supply and system power to stabilize before

the reset sequences are released.

BLOCK DIAGRAM Figure 1

OPERATION — TOLERANCE SELECT

The DS1830/A provides a TOL input for individual customization of the DS1830x to specific application

requirements (see Table 1). For the tolerance selection, see Table 1 below. The TOL input is only

sampled while VCC is below the lowest potential trip value and can not be changed after the VCC voltage

exceeds the lowest potential trip value.

TOL — TOLERANCE SELECT Table 1

TOL 5V (DS1830) 3.3V (DS1830A)

VCC 5% 5%

GND 10% 10%

OPEN

(N.C.) 15% 20%

D1830/A

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OPERATION — PUSHBUTTON RESET

The DS1830 provides a pushbutton switch for manual reset control. When any of the DS1830/A resets

are not active (low) a reset cycle can be initiated by a pushbutton reset. The pushbutton reset is generated

by pulling the PBRST pin low for at least 1ms. When the push- button is held low all resets are forced

active. The reset will remain active until the pushbutton input is released and then will start a sequenced

time-out based on the condition of the TD input. The Pushbutton input is pulled high through an internal

40kW pull-up resistor and debounced via internal circuitry. See Figure 2 for an application example and

Figure 3 for the timing diagram.

PUSHBUTTON RESET Figure 2

TIMING DIAGRAM — PUSHBUTTON RESET Figure 3

OPERATION — TIME DELAY SELECT

The DS1830 provides an input to select three time delay characteristics for the reset outputs. The TD

input has 3 states high (VCC), low (ground) and no connect (N.C.). Table 2 details the minimum timing

based on the state of the TD input. If the TD input is connected to ground; RST1 will have a minimum

time delay of 10 ms after VCC is in tolerance. If the TD input is floated; RST1 will have a minimum time

delay of 20 ms after VCC is in tolerance. If the TD input is connected to VCC, RST1 will have a minimum

time delay of 50 ms after VCC is in tolerance. An oscillator and clock chain generate the reset timing with

each time delay based on the same device oscillator. The time delay for RST2 will be 5 times as long as

RST1 and RST3 will be 10 times the duration of RST1 .

TD CONTROL MINIMUM RESET TIMING Table 2

TD TRST1 TRST2 TRST3

TD = GND 10ms 50ms 100ms

TD = N.C. 20ms 100ms 200ms

TD = VCC 50ms 250ms 500ms

D1830/A

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APPLICATION DIAGRAM — CASCADE DELAY CONFIGURATIONS Figure 4

Note 1: The RST3 output tied to the pushbutton reset would be pulled to VCC through the 40kW resistor in

the pushbutton input. If a stronger pull-up is required an additional pull-up resistor could be added.

Note 2: When using the cascade configuration, it is important that the TOL pins of the master and the

slave are configured so that the master’s VCCTP is greater than the slave’s VCCTP. This will ensure that

when the master’s higher VCCTP is crossed, the resets will ripple through to the slave.

TIMING DIAGRAM — POWER-DOWN Figure 5

MASTER

SLAVE

SEE NOTE 2

SEE NOTE 1

D1830/A

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TIMING DIAGRAM — POWER-UP Figure 6

ABSOLUTE MAXIMUM RATINGS*

Voltage on any Pin Relative to

Ground

-0.5V to +6.0V

Operating Temperature -40°C to +85°C

Storage Temperature -55°C to +125°C

Soldering Temperature See IPC/JEDEC J-STD-020A

* This is a stress rating only and functional operation of the device at these or any other conditions above

those indicated in the operation sections of this specification is not implied. Exposure to absolute

maximum rating conditions for extended periods of time may affect reliability.

RECOMMENDED DC OPERATING CONDITIONS (-40°C to +85°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Supply Voltage VCC 1.0 5.5 V 1

PBRST Input High

Level VIH 2.0 VCC + 0.3 V

PBRST Input Low

Level VIL -0.3 +0.5 V

D1830/A

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DC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC = 1.0V to 5.5V)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

VCC Trip Point (TOL=

VCC) DS1830 VCCTP 4.50 4.62 4.74 V

VCC Trip Point

(TOL=GND) DS1830 VCCTP 4.25 4.37 4.49 V

VCC Trip Point

(TOL=Open) DS1830 VCCTP 4.00 4.13 4.24 V

VCC Trip Point (TOL=

VCC) DS1830A VCCTP 2.98 3.06 3.15 V

VCC Trip Point

(TOL=GND) DS1830A VCCTP 2.80 2.88 2.97 V

VCC Trip Point

(TOL=Open) DS1830A VCCTP 2.47 2.55 2.64 V

Input Leakage IIL -1.0 +1.0 µA2

Output Current @ 0.4V IOL 20 mA 3

DS1830 18 35

Operating Current

(Standby) ICC DS1830A 10 25 µA4

AC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC = 1.0V to 5.5V)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

PBRST = VIL tPB tPDLY ms

RESET Active Time

(RST1 /TD =GND) tRST1 10 15 20 ms

RESET Active Time

(RST1 /TD =Float) tRST1 20 30 40 ms

RESET Active Time

(RST1 /TD = VCC)tRST1 50 75 100 ms

RESET Active Time

(RST2 )tRST2

tRST1ms

RESET Active Time

(RST3 )tRST3

10x

tRST1ms

VCC Detect to RST tRPD 58µs5

VCC Slew Rate tF20 µs6

VCC Detect to RST tRPU

See RESET Active

Times ms 7

VCC Slew Rate tR0ns

PBRST Stable Low to

RST tPDLY 1.0 1.5 2.0 ms

CAPACITANCE (TA = +25°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Capacitance CIN 5pF

Output Capacitance COUT 7pF

D1830/A

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NOTES:

1. All voltages are referenced to ground.

2. PBRST is internally pulled up to VCC with an internal impedance of 40kW typical.

3. Measured with PBRST = VCC and RST1 , RST2 , and RST3 open.

4. Measured with outputs open and all inputs at VCC or Ground (except TD and TOL can be floating).

5. Noise Immunity - Pulses < 2ms at VCC TP minimum will not cause a reset.

6. The tF value is for reference in defining values for tRPD and should not be considered a requirement for

proper operation or use of the device.

7. See tRST1, tRST2, and tRST3 for specific tRPU AC timing parameters.

ORDERING INFORMATION

PART # PIN PACKAGE TEMP TYPE

DS1830 8-DIP 300-MIL -40°C to +85°C5V Reset Sequencer

DS1830S 8-SO 150-MIL -40°C to +85°C5V Reset Sequencer

DS1830U 8-µSOP 118-MIL -40°C to +85°C5V Reset Sequencer

DS1830A 8-DIP 300-MIL -40°C to +85°C3.3V Reset Sequencer

DS1830AS 8-SO 150-MIL -40°C to +85°C3.3V Reset Sequencer

DS1830AU 8-µSOP 118-MIL -40°C to +85°C3.3V Reset Sequencer