TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
Linear Constant Current Regulated LED Driver
DESCRIPTION
FEATURES
The TSCR420 & TSCR421 are Low-Side 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 300mA. It is
designed for driving LEDs in strings and will reduce
● AEC-Q100 qualified with the following results:
Device temperature grade 1: -40°C to 125°C
Device HBM ESD classification level H2
Device CDM ESD classification level C6
● LED drive current preset to 10mA
● Continuous output current up to 300mA with an
external resistor
● Very low enable current
● Easy paralleling of drivers to increase current
● Supply voltage up to 40V
● Digital PWM input up to 10kHz (TSCR421)
● Good temperature coefficient vs. output current
● Compliant to RoHS Directive 2011/65/EU and in
accordance to WEEE 2002/96/EC.
● Halogen-Free according to IEC 61249-2-21
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 2.0V, VEN=24V
TSCR421
VOUT>2.0V, VEN=3.3V
IOUT
mA
Voltage Drop (VREXT)
IOUT=10mA
VDROP
0.85
0.95
1.05
V
Minimum Output Voltage
IOUT>18mA
VOUT(MIN)
--
1.4
--
V
--
-0.07
--
--
-0.07
--
--
0.33
--
--
0.33
--
Output Current
vs. Temperature
TSCR420
VOUT>2.0V, VEN=24V
TSCR421
VOUT>2.0V, VEN=3.3V
Output Current
vs. Supply Voltage
TSCR420
VOUT>2.0V, VEN=24V
TSCR421
VOUT>2.0V, VEN=3.3V
2
ΔIOUT/IOUT
ΔIOUT/IOUT
%/°C
%/V
Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
ORDERING INFORMATION
ORDERING CODE
PACKAGE
PACKING
TSCR420CX6H RFG
SOT-26
3,000pcs / 7”Reel
TSCR421CX6H RFG
SOT-26
3,000pcs / 7”Reel
FUNCTION BLOCK
OUT
EN
Regulator
Vref
Vref
REXT
RINT
GND
TSCR420/TSCR421
PIN DESCRIPTION
PIN NO.
NAME
FUNCTION
1
EN
2
OUT
Regulated output current
3
OUT
Regulated output current
4
GND
Power ground
5
OUT
Regulated output current
6
REXT
External resistor for adjusting output current
Enable for biasing transistor
3
Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
TSCR420CX6 CHARACTERISTICS CURVES
Figure 2. VOUT vs. IOUT (REXT=20Ω)
Figure 1. VOUT vs. IOUT (REXT=open)
Figure 3. VOUT vs IOUT (REXT=8.2Ω)
Figure 4. VEN vs IOUT (REXT=open)
Figure 5. VEN vs. IOUT (REXT=20Ω)
Figure 6. VEN vs. IOUT (REXT=8.2Ω)
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Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
TSCR420CX6 CHARACTERISTICS CURVES
Figure 7. VEN vs. IEN (REXT=open)
Figure 8. VEN vs. IEN (REXT=20Ω)
Figure 9. VEN vs. IEN (REXT=8.2Ω)
5
Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
TSCR421CX6 CHARACTERISTICS CURVES
Figure 10. VOUT vs. IOUT (REXT=open)
Figure 11. VOUT vs. IOUT (REXT=20Ω)
Figure 12. VOUT vs. IOUT (REXT=8.2Ω)
Figure 13. VEN vs. IOUT (REXT=open)
Figure 14. VEN vs. IOUT (REXT=20Ω)
Figure 15. VEN vs. IOUT (REXT=8.2Ω)
6
Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
TSCR421CX6 CHARACTERISTICS CURVES
Figure 16. VEN vs. IEN (REXT =open)
Figure 17. VEN vs. IEN (REXT =20Ω)
Figure 18. VEN vs. IEN (REXT=8.2Ω)
Figure 19. PD vs. Ambient Temperature
7
Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
APPLICATION INFORMATION
The TSCR420 & TSCR421 are designed for driving low current LEDs with typical LED currents of 10mA to 300mA.
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 20 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 TSCR421; or VEN = 24V and VOUT = 1.4V for TSCR420. 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 R EXT will
improve the overall accuracy of the current sense formed by the parallel connection of RINT and REXT.
REXT = VDROP / (IOUT – (VDROP/RINT))
Two or more TSCR420 & TSCR421 can be connected in parallel to construct higher current LED strings as shown
in Figure 21. Consideration of the expected linear mode power dissipation must be factored into the design, with
respect to the TSCR420 & TSCR421’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– VREXT) × ILED + (VEN × IEN)
As the output current of TSCR420 & TSCR421 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.
Vs Supply
Vs Supply
LED
String
LED
String
Vref
Vref
OUT
Regulator
Vref
Vref
CEN
CEN
OUT
Regulator
Vref
Vref
REXT
REXT
RINT
EN
RINT
(Optional)
Figure 20: Typical Application Circuit for
Linear Mode Current Sink LED Driver
REXT
RINT
(Optional)
GND
GND
TSCR420
TSCR421
Regulator
EN
TSCR420
TSCR421
OUT
TSCR420
TSCR421
CEN
EN
(Optional)
GND
Figure 21: Application Circuit for Increasing LED Current
8
Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
APPLICATION INFORMATION (CONTINUE)
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 22.
Vs Supply
Vs Supply
LED
String
LED
String
µC
CEN
EN
OUT
EN
OUT
Regulator
Vref
Regulator
Vref
Vref
CEN
Vref
REXT
RINT
REXT
(Optional)
RINT
GND
(Optional)
GND
TSCR421
TSCR420
Figure 22: Application Circuit for LED Driver with
PWM Dimming Functionality
Figure 23: Application Circuit for LED Driver with
High voltage EN Pin
9
Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
PACKAGE OUTLINE DIMENSIONS (Unit: Millimeters)
SOT-26
SUGGESTED PAD LAYOUT (Unit: Millimeters)
MARKING DIAGRAM
Nx = Device Code
N1 =TSCR420CX6
N2 =TSCR421CX6
Y = Year Code
M = Month Code for Halogen Free Product
O =Jan P =Feb Q =Mar R =Apr
S =May T =Jun U =Jul
V =Aug
W =Sep X =Oct
Y =Nov Z =Dec
L = Lot Code (1~9, A~Z)
10
Version: A1812
TSCR420CX6H / TSCR421CX6H
Taiwan Semiconductor
Notice
Specifications of the products displayed herein are subject to change without notice. TSC or anyone on its behalf,
assumes no responsibility or liability for any errors or inaccuracies.
Information contained herein is intended to provide a product description only. No license, express or implied, to
any intellectual property rights is granted by this document. Except as provided in TSC’s terms and conditions of
sale for such products, TSC assumes no liability whatsoever, and disclaims any express or implied warranty,
relating to sale and/or use of TSC products including liability or warranties relating to fitness for a particular
purpose, merchantability, or infringement of any patent, copyright, or other intellectual property right.
The products shown herein are not designed for use in medical, life-saving, or life-sustaining applications.
Customers using or selling these products for use in such applications do so at their own risk and agree to fully
indemnify TSC for any damages resulting from such improper use or sale.
11
Version: A1812
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