BCR420UW6Q / BCR421UW6Q
Document number: DS38302 Rev. 4 - 2
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BCR420UW6Q / BCR421UW6Q
LINEAR LED CONSTANT CURRENT REGULATOR IN SOT26
Description
These Linear LED drivers are designed to meet the stringent
requirements of automotive applications.
The BCR420UW6Q and BCR421UW6Q monolithically integrate
transistors, diodes and resistors to function as a Constant Current
Regulator (CCR) for linear LED driving. The device regulates with a
preset 10mA nominal that can be adjusted with an external resistor up
to 350mA. It is designed for driving LEDs in strings and will reduce
current at increasing temperatures to self-protect. Operating as a
series linear CCR for LED string current control, it can be used in
multiple applications, as long as the maximum supply voltage to the
device is < 40V.
With the low-side control, the BCR421UW6Q has an Enable (EN) pin
which can be pulse-width modulated (PWM) up to 25 kHz by a micro-
controller for LED dimming.
With no need for additional external components, this CCR is fully
integrated into an SOT26 minimizing PCB area and component count.
Applications
Constant Current Regulation (CCR) in:
Automotive Interior Lighting
Mood and Decorative Lighting
Features
LED Constant Current Regulator using NPN Emitter-Follower with
Emitter Resistor to Current Limit
IOUT – 10mA ± 10% Constant Current (Preset)
IOUT up to 350mA Adjustable with an External Resistor
(BCR421UW6Q)
VOUT – 40V Supply Voltage
PD up to 1W in SOT26 (SC74R)
Low-Side Control Enabling PWM Input < 25kHz (BCR421UW6Q)
Negative Temperature Coefficient (NTC) Reduces IOUT with
Increasing Temperature
Parallel Devices to Increase Regulated Current
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Qualified to AEC-Q101 Standards for High Reliability
PPAP Capable (Note 4)
Mechanical Data
Case: SOT26 (SC74R)
Case Material: Molded Plastic. “Green” Molding Compound.
UL Flammability Rating 94V-0
Moisture Sensitivity: Level 1 per J-STD-020
Terminals: Finish - Matte Tin Plated Leads.
Solderable per MIL-STD-202, Method 208
Weight: 0.018 grams (Approximate)
REXT
(Optional)
GND
BCR420U
BCR421U
EN OUT
Ordering Information (Note 5)
Product
Marking
Reel Size (inches)
Tape Width (mm)
Quantity per Reel
BCR420UW6Q-7
420
7
8
3,000
BCR421UW6Q-7
421
7
8
3,000
Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS), 2011/65/EU (RoHS 2) & 2015/863/EU (RoHS 3) compliant.
2. See https://www.diodes.com/quality/lead-free/ for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green" and
Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine
(<1500ppm total Br + Cl) and <1000ppm antimony compounds.
4. Automotive products are AEC-Q101 qualified and are PPAP capable. Refer to http://www.diodes.com/product_compliance_definitions.html.
5. For packaging details, go to our website at https://www.diodes.com/design/support/packaging/diodes-packaging/.
Pin Name
Pin Function
OUT
Regulated Output Current
EN
Enable for Biasing
Transistor
REXT
External Resistor for
Adjusting Output Current
GND
Power Ground
Top View
Pin-Out
SOT26 (SC74R )
Top View
EN
OUT
OUT
REXT
GND
OUT
Internal Device
Schematic
BCR420UW6Q / BCR421UW6Q
Document number: DS38302 Rev. 4 - 2
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BCR420UW6Q / BCR421UW6Q
Marking Information
Date Code Key
Year
2017
2018
2019
2020
2021
2022
2023
Code
E
F
G
H
I
J
K
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Code
1
2
3
4
5
6
7
8
9
O
N
D
Absolute Maximum Ratings (Voltage relative to GND, @TA = +25°C, unless otherwise specified.)
Characteristic
Symbol
Value
Unit
Enable Voltage
BCR420UW6Q
VEN
40
V
BCR421UW6Q
18
Output Current
IOUT
500
mA
Output Voltage
VOUT
40
V
Reverse Voltage Between all Terminals
VR
0.5
V
Thermal Characteristics (@TA = +25°C, unless otherwise specified.)
Characteristic
Symbol
Value
Unit
Power Dissipation
(Note 6)
PD
1,190
mW
(Note 7)
912
Thermal Resistance, Junction to Ambient
(Note 6)
RθJA
105
°C/W
(Note 7)
137
Thermal Resistance, Junction to Lead
(Note 8)
RθJL
50
Recommended Operating Junction Temperature Range
TJ
-55 to +150
°C
Maximum Operating Junction and Storage Temperature Range
TJ , TSTG
-65 to +150
ESD Ratings (Note 9)
Characteristics
Symbols
Value
Unit
JEDEC Class
Electrostatic Discharge – Human Body
Model
BCR420UW6Q
HBM
500
V
1B
BCR421UW6Q
1,000
V
1C
Electrostatic Discharge – Machine
Model
BCR420UW6Q
MM
300
V
B
BCR421UW6Q
400
V
C
Notes: 6. For a device mounted with the OUT leads on 50mm x 50mm 1oz copper that is on a single-sided 1.6mm FR-4 PCB; device is measured under still
air conditions while operating in steady-state.
7. Same as Note 5, except mounted on 25mm x 25mm 1oz copper.
8. RθJL = Thermal resistance from junction to solder-point (at the end of the OUT leads).
9. Refer to JEDEC specification JESD22-A114 and JESD22-A115.
xxx = Part Marking (See Ordering Information)
YM = Date Code Marking
Y = Year (ex: E = 2017)
M = Month (ex: 9 = September)
xxx
SOT26 (SC74R)
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Electrical Characteristics (@TA = +25°C, unless otherwise specified.)
Characteristic
Symbol
Min
Typ
Max
Unit
Test Condition
Collector-Emitter Breakdown Voltage
BVCEO
40
—
—
V
IC = 1mA
Enable Current
BCR420UW6Q
IEN
—
1.2
—
mA
VEN = 24V
BCR421UW6Q
—
1.2
—
VEN = 3.3V
DC Current Gain
hFE
200
350
500
—
IC = 50mA; VCE = 1V
Internal Resistor
RINT
85
95
105
Ω
IRINT = 10mA
Bias Resistor
BCR420UW6Q
RB
—
20
—
kΩ
—
BCR421UW6Q
—
1.5
—
—
Output Current
BCR420UW6Q
IOUT
9
10
11
mA
VOUT = 1.4V; VEN = 24V
BCR421UW6Q
9
10
11
mA
VOUT = 1.4V; VEN = 3.3V
Output Current at
REXT = 5.1Ω
BCR420UW6Q
IOUT
—
150
—
mA
VOUT > 2.0V; VEN = 24V
BCR421UW6Q
—
150
—
mA
VOUT > 2.0V; VEN = 3.3V
Voltage Drop (VREXT)
VDROP
0.85
0.95
1.05
V
IOUT = 10mA
Minimum Output Voltage
VOUT(MIN)
—
1.4
—
V
IOUT > 18mA
Output Current Change
vs. Temperature
BCR420UW6Q
ΔIOUT/IO
UT
—
-0.2
—
%/°C
VOUT > 2.0V; VEN = 24V
BCR421UW6Q
—
-0.2
—
VOUT > 2.0V; VEN = 3.3V
Output Current Change
vs. Supply Voltage
BCR420UW6Q
ΔIOUT/IO
UT
—
1
—
%/V
VOUT > 2.0V; VEN = 24V
BCR421UW6Q
—
1
—
VOUT > 2.0V; VEN = 3.3V
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Typical Thermal Characteristics BCR420UW6Q/BCR421UW6Q (@TA = +25°C, unless otherwise specified.)
100 1000
0
100
200
300
400
500
600
700
800
Rth(JA) VS Cu Area
Copper Area (mm2)
100μ 1m 10m 100m 110 100 1k
0
25
50
75
100
125
Tamb=25oC
50mm * 50mm
1oz Cu
Transient Thermal Impedance
D=0.5
D=0.2
D=0.1
Single Pulse
D=0.05
Thermal Resistance (oC/W)
Pulse Width (s) 100μ 1m 10m 100m 110 100 1k
1
10 Tamb=25oC
50mm * 50mm
1oz Cu
Single Pulse
Pulse Power Dissipation
Pulse Width (s)
Maximum Power (W)
100μ 1m 10m 100m 110 100 1k
0
25
50
75
100
125
150
Tamb=25oC
25mm * 25mm
1oz Cu
Transient Thermal Impedance
D=0.5
D=0.2
D=0.1
Single Pulse
D=0.05
Thermal Resistance (oC/W)
Pulse Width (s) 100μ 1m 10m 100m 110 100 1k
1
10 Single Pulse
Tamb=25oC
25mm * 25mm
1oz Cu
Pulse Power Dissipation
Pulse Width (s)
Maximum Power (W)
050 100 150
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Rth(JA) (oC/W)
25mm * 25mm
1oz Cu
50mm * 50mm
1oz Cu
Derating Curve
Temperature (oC)
Max Power Dissipation (W)
µ
µ
µ
µ
BCR420UW6Q / BCR421UW6Q
Document number: DS38302 Rev. 4 - 2
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BCR420UW6Q / BCR421UW6Q
Typical Electrical Characteristics BCR421UW6Q (Cont.) (@TA = +25°C, unless otherwise specified.)
0 2 4 6 8 10 12
0.00
0.01
0.02
110 100
0.00
0.05
0.10
0.15
0.20
012345678910 11 12
0.00
0.04
0.08
0.12
0.16
0.20
0246810 12
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0246810 12
0.02
0.03
0.04
0.05
0.06
0 1 2 3 4 5
0.00
0.05
0.10
0.15
REXT=open
VEN=3.3V
85oC
25oC
-40oC
VEN=3.3V
IOUT (A) IOUT (A)
IOUT (A) IOUT (A)
VOUT=5.4V
VOUT=1.4V
IOUT (A)
IOUT (A)
VEN vs IOUT
VOUT (V)
VOUT vs IOUT
VOUT vs IOUT
VOUT (V)
VOUT vs IOUT
VOUT (V)
REXT ()
REXT=15REXT= 30
REXT=open
REXT=10
REXT=8.2
REXT=6.2
VOUT vs IOUT
VEN=3.3V
VOUT (V)
REXT=6.2
VEN=3.3V
25oC
REXT () vs IOUT
85oC
-40oC
REXT=20
VEN=3.3V
85oC
25oC
-40oC
VOUT=2V
REXT= 60REXT= open
REXT=30
REXT=6.2
REXT=8.2
REXT=10
VEN (V)
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Typical Electrical Characteristics BCR421UW6Q (cont.) (@TA = +25°C, unless otherwise specified.)
0 1 2 3 4 5
0.000
0.005
0.010
0.015
0 1 2 3 4 5
0.0
500.0μ
1.0m
1.5m
2.0m
2.5m
3.0m
0 1 2 3 4 5
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0 1 2 3 4 5
0.00
0.05
0.10
0.15
0.20
REXT=open
VOUT=2V
85oC
25oC
-40oC
IOUT (A)
IOUT (A)
VEN (V) VEN (V)
VEN (V)
VEN (V)
REXT=open 85oC
25oC-40oC
IOUT (A)
I OUT=0A
IEN (mA)
VEN vs IOUT
VENvs IOUT
VENvs IOUT
REXT=6.2
VOUT=2V
25oC
VENvs IEN
85oC
-40oC
REXT= 20
VOUT=2V
85oC
25oC
-40oC
500.0µ
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Typical Electrical Characteristics BCR420UW6Q (cont.) (@TA = +25°C, unless otherwise specified.)
0 2 4 6 8 10 12
0.00
0.01
0.02
110 100
0.00
0.05
0.10
0.15
0.20
0 1 2 3 4 5 6 7 8 9 10 11 12
0.00
0.04
0.08
0.12
0.16
0.20
0246810 12
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0 2 4 6 8 10 12
0.02
0.03
0.04
0.05
0.06
0 5 10 15 20 25 30
0.00
0.05
0.10
0.15
REXT=open
VEN=24V
85oC
25oC
-40oC
VEN=24V
IOUT (A) IOUT (A)
IOUT (A) IOUT (A)
VOUT = 5.4V
VOUT=1.4V
IOUT (A)
IOUT (A)
VEN vs IOUT
VOUT (V)
VOUT vs IOUT
VOUT vs IOUT
VOUT (V)
VOUT vs IOUT
VOUT (V)
REXT ()
REXT=15
REXT= 30
REXT=open
REXT=10
REXT=8.2
REXT=6.2
VOUT vs IOUT
VEN=24V
VOUT (V)
REXT=6.2
VEN=24V
25oC
REXT ()vs IOUT
85oC
-40oC
REXT=20
VEN=24V
85oC
25oC
-40oC
VOUT=2V
REXT=60REXT=open
REXT=30
REXT=20
REXT=8
Rext=10
VEN (V)
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Typical Electrical Characteristics BCR420UW6Q (cont.) (@TA = +25°C, unless otherwise specified.)
0 5 10 15 20 25 30
0.000
0.005
0.010
0.015
0 5 10 15 20 25 30 35 40
0.0
500.0μ
1.0m
1.5m
2.0m
2.5m
3.0m
0 5 10 15 20 25 30
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0 5 10 15 20 25 30
0.00
0.05
0.10
0.15
0.20
REXT=open
VOUT=2V
85oC
25oC
-40oC
IOUT (A)
IOUT (A)
VEN (V) VEN (V)
VEN (V)
VEN (V)
REXT=open 85oC
25oC-40oC
IOUT (A)
I OUT=0A
IEN (mA)
VENvs IOUT
VENvs IOUT
VENvs IOUT
REXT=6.2
VOUT=2V
25oC
VENvs IEN
85oC
-40oC
REXT=20
VOUT=2V
85oC
25oC
-40oC
500.0µ
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Application Information
Figure 1 Typical Application Circuit for
Linear Mode Current Sink LED Driver
Figure 2 Application Circuit for Increasing LED Current
The BCR420UW6Q/BCR421UW6Q are designed for driving low current
LEDs with typical LED currents of 10mA to 350mA. They provide a cost-
effective way for driving low current LEDs compared with more complex
switching regulator solutions. Furthermore, they reduce the PCB board
area of the solution as there is no need for external components like
inductors, capacitors and switching diodes.
Figure 1 shows a typical application circuit diagram for driving an LED
or string of LEDs. The device comes with an internal resistor (RINT) of
typically 95Ω, which in the absence of an external resistor, sets an LED
current of 10mA (typical) from a VEN = 3.3V and VOUT = 1.4V for
BCR421; or VEN = 24V and VOUT = 1.4V for BCR420. LED current can
be increased to a desired value by choosing an appropriate external
resistor, REXT.
The REXT Vs IOUT graphs should be used to select the appropriate
resistor. Choosing a low tolerance REXT will improve the overall
accuracy of the current sense formed by the parallel connection of RINT
and REXT.
Two or more BCR420UW6Q/BCR421UW6Q can be connected in
parallel to construct higher current LED strings as shown in Figure 2.
Consideration of the expected linear mode power dissipation must be
factored into the design, with respect to the
BCR420UW6Q/BCR421UW6Q’s thermal resistance. The maximum
voltage across the device can be calculated by taking the maximum
supply voltage and subtracting the voltage across the LED string.
VOUT = VS – VLED
PD = (VOUT × ILED) + (VEN × IEN)
As the output current of BCR420UW6Q/BCR421UW6Q increases, it is
necessary to provide appropriate thermal relief to the device. The power
dissipation supported by the device is dependent upon the PCB board
material, the copper area and the ambient temperature. The maximum
dissipation the device can handle is given by:
PD = (TJ(MAX) - TA) / RθJA
Refer to the thermal characteristic graphs on Page 4 for selecting the
appropriate PCB copper area.
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Application Information (continued)
PWM dimming can be achieved by driving the EN pin. Dimming is achieved by turning the LEDs ON and OFF for a portion of a single cycle. The
PWM signal can be provided by a micro-controller or analog circuitry; typical circuit is shown in Figure 3. Figure 4 is a typical response of LED
current vs. PWM duty cycle on the EN pin. PWM up to 25kHz with duty cycle of 0.5% (dimming range 200:1). This is above the audio band
minimizing audible power supply noise.
Figure 3 Application Circuits for LED Driver with PWM Dimming Functionality using BCR421UW6Q
Figure 4 Typical LED Current Response vs. PWM Duty Cycle for
25kHz PWM Frequency (Dimming Range 200:1)
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Application Information (cont.)
To remove the potential of incorrect connection of the power supply
damaging the lamp’s LEDs, many systems use some form of
reverse polarity protection.
One solution for reverse input polarity protection is to simply use a
diode with a low VF in line with the driver/LED combination. The low
VF increases the available voltage to the LED stack and dissipates
less power. A circuit example is presented in Figure 5 which
protects the light engine although it will not function until the problem
is diagnosed and corrected. An SDM10U45LP (0.1A/45V) is shown,
providing exceptionally low VF for its package size of 1mm x 0.6mm.
Other reverse voltage ratings are available from Diodes
Incorporated’s website such as the SBR02U100LP (0.2A/100V) or
SBR0220LP (0.2A/20V).
While automotive applications commonly use this method for
reverse battery protection, an alternative approach shown in Figure
6, provides reverse polarity protection and corrects the reversed
polarity, allowing the light engine to function.
The BAS40BRW incorporates four low VF Schottky diodes in a
single package, reducing the power dissipated and maximizes the
voltage across the LED stack.
Figure 7 shows an example configuration for 350mA operation using
BCR421UW6Q. In such higher current configurations adequate
enable current is provided by increasing the enable voltage.
Figure 5 Application Circuit for LED Driver
with Reverse Polarity Protection
Figure 6 Application Circuit for LED Driver with
Assured Operation Regardless Of Polarity
Figure 7 Example for 350mA Operation using BCR421UW6Q
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
Package Outline Dimensions
Please see http://www.diodes.com/package-outlines.html for the latest version.
Suggested Pad Layout
Please see http://www.diodes.com/package-outlines.html for the latest version.
a1
D
e
E1 E
b
A2 A1
Seating Plane
L
c
a
e1
A3
SOT26 (SC74R)
Dim
Min
Max
Typ
A1
0.013
0.10
0.05
A2
1.00
1.30
1.10
A3
0.70
0.80
0.75
b
0.35
0.50
0.38
c
0.10
0.20
0.15
D
2.90
3.10
3.00
e
-
-
0.95
e1
-
-
1.90
E
2.70
3.00
2.80
E1
1.50
1.70
1.60
L
0.35
0.55
0.40
a
-
-
8°
a1
-
-
7°
All Dimensions in mm
Dimensions
Value (in mm)
C
2.40
C1
0.95
G
1.60
X
0.55
Y
0.80
Y1
3.20
C1
Y1 G
X
Y
C
SOT26 (SC74R)
SOT26 (SC74R)
BCR420UW6Q / BCR421UW6Q
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BCR420UW6Q / BCR421UW6Q
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
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Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and
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This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the
final and determinative format released by Diodes Incorporated.
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Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the
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Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and
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representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
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