TS19378
Taiwan Semiconductor
2A Buck (Step-down) WLED Driver
DESCRIPTION
The TS19378 is a high voltage step-down converter
designed for driving up to 10 series white LEDs from a
40V system input. The total LED driving current up to
2A, which is measured through an external current
sense resistor. Its low 200mV feedback voltage
reduces power loss and improves efficiency. The OVP
pin monitors the output voltage and turns off the
converter if an over-voltage condition is present due to
an open circuit condition. The TS19378 includes
current limit, short circuit protection and thermal
shutdown protection preventing damage.
TS19378 provides high power, high efficiency, and
excellent transient characteristics. The PWM control
circuit is able to the duty ratio linearly from 0 up to
100%. Since this converter can accommodate an
input voltage up to 40V, it is also suitable for the
operation via an AC adapter.
FEATURES
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Input Voltage Range 8V~40V
Output voltage up to 38V
2A Switch Output Current
Duty ratio: 0%~100% PWM control
300kHz Switching Frequency
Enable/Disable Functions
Soft Start Time Control
Current limit and Thermal Shutdown
Short Circuit Protections
Built-in Internal SW P-CH MOSFET
APPLICATION
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White LED Backlighting
High Power LED Application
Multiple LED Driving
LED Lighting Equipment
SOP-8EP
Pin Definition:
1. EN/SS
2. GND
3. V
GATE
4. V
CC
8. COMP
7. FB
6. OVP
5. SW (Connected to exposed pad)
Notes:
Moisture sensitivity level: level 3. Per J-STD-020
TYPICAL APPLICATION CIRCUIT
C
OUT
ESR Range
30~80mΩ
80~300mΩ
R2
470R
100R
C7
10nF
15nF
Document Number: DS_P0000199
1
Version: B15
TS19378
Taiwan Semiconductor
ABSOLUTE MAXIMUM RATINGS
(T
A
= 25°C unless otherwise specified)
(Note 1)
PARAMETER
V
CC
Pin Voltage
Feedback Pin Voltage
EN/SS Pin Voltage
OVP Pin Voltage
COMP Pin Voltage
VGATE Pin Voltage
Switch Pin Voltage
Power Dissipation
Storage Temperature Range
Operating Junction Temperature Range
Operating Supply Voltage
Output Voltage
SYMBOL
V
CC
V
FB
V
EN/SS
V
OVP
V
COMP
V
GATE
V
SW
PD
T
ST
T
OJP
V
OP
V
OUT
(Note 2)
LIMIT
V
SS
- 0.3 to V
SS
+ 45
V
SS
- 0.3 to 6
V
SS
- 0.3 to 6
V
SS
- 0.3 to V
CC
V
SS
- 0.3 to 6
V
SS
- 0.3 to V
CC
V
SS
- 0.3 to V
CC
+ 0.3
Internally limited
-65 to +150
-40 to +125
8 to 40
38
UNIT
V
V
V
V
V
V
V
mW
°C
°C
V
V
THERMAL PERFORMANCE
PARAMETER
SYMBOL
R
ӨJC
R
ӨJA
LIMIT
15
40
UNIT
o
o
Thermal Resistance from Junction to Case
Thermal Resistance from Junction to Ambient
C/W
C/W
ELECTRICAL SPECIFICATIONS
(T
A
= 25°C unless otherwise specified)
PARAMETER
Feedback Voltage
Quiescent Current
Feedback Bias Current
Shutdown Supply Current
Switch Current Limit
Oscillation Frequency
Short Frequency
EN/SS Pin Shutdown Logic
input threshold voltage
EN/SS Pin Input Current
Internal MOSFET R
DSON
OVP Sense Voltage
Thermal shutdown Temp
Thermal shutdown Hysteresis
SYMBOL
V
FB
I
CCQ
I
FB
I
SD
I
SWLIMIT
f
OSC
f
OSC
V
SL
I
EN/SS
R
DSON
V
OVP
T
SD
T
SH
Low (regulator OFF)
V
EN
=0V
V
CC
=5V, V
FB
=0V
CONDITION
I
OUT
=0.2A
V
FB
=0.5V force driver off
I
OUT
=0.1A
V
EN
=0V
MIN
0.19
--
--
--
2.5
240
--
--
--
--
0.833
--
--
TYP
0.20
3
0.1
150
--
300
50
--
5
130
0.850
150
40
MAX
0.21
6
0.5
300
--
360
--
0.8
--
180
0.867
--
--
UNIT
V
mA
μA
μA
A
kHz
kHz
V
μA
mΩ
V
°C
°C
Note:
1.
Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. 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
remain possibility to affect device reliability.
2.
R
ӨJA
is measured with the PCB copper area(need connect to Exposed Pad) of approximately 1.5 in
2
(Multi-layer).
Document Number: DS_P0000199
2
Version: B15
TS19378
Taiwan Semiconductor
ORDERING INFORMATION
PART NO.
TS19378CS RLG
PACKAGE
SOP-8EP
PACKING
2,500pcs / 13” Reel
Note:
1. Compliant to RoHS Directive 2011/65/EU and in accordance to WEEE 2002/96/EC.
2. Halogen-free according to IEC 61249-2-21 definition.
FUNCTION BLOCK
PIN DESCRIPTION
PIN NO.
1
2
3
4
5
6
7
8
NAME
EN/SS
GND
VGATE
V
CC
SW
OVP
FB
COM
FUNCTION
EN: Output stage enable control pin. It can be left floating for normally on.
SS: Supplied shutdown or soft start function.
Ground return for all internal circuitry.
Gate drive for external N-CH MOSFET.
Power supply pin for all internal circuitry.
SW is the output of the internal driver switch. Connected for package exposed pad
Output voltage protection.
Feedback pin. Reference voltage is V
FB
=0.2V.
Output pin of error amplifier.
Document Number: DS_P0000199
3
Version: B15
TS19378
Taiwan Semiconductor
TYPICAL APPLICATION CIRCUIT
AC Input Application Circuit
I
LED
350mA
750mA
1000mA
0.570Ω
0.266Ω
0.200Ω
R5
70mW
150mW
200mW
C1
100μF
220μF
330μF
L1
33μH
APPLICATION INFORMATION
PWM Control
The TS19378 consists of DC/DC converters that employ a pulse-width modulation (PWM) system. In converters of
the TS19378, the pulse width varies in a range from 0 to 100%, according to the load current. The ripple voltage
produced by the switching can easily be removed through a filter because the switching frequency remains constant.
Therefore, these converters provide a low-ripple power over broad ranges of input voltage and load current
Setting ILED Current
Application circuit item shows the basic application circuit with TS19378 adjustable output version. The external
resistor sets the LED output current according to the following formula:
I
LED
=(0.25V/R5), V
FB
=0.2V
Resistor select for LED output current setting
I
LED
350mA
750mA
1000mA
Current Limit
The current limit threshold is setting by the internal circuit.
Compensation
In all LED driver applications. Connecting a resistor (R2) and a capacitor (C7) from COMP pin to GND. Please
refer the application circuit table to design.
0.57Ω
0.266Ω
0.2Ω
R2
70mW
150mW
200mW
Document Number: DS_P0000199
4
Version: B15
TS19378
Taiwan Semiconductor
APPLICATION INFORMATION (CONTINUE)
EN/SS
This pin can be supplied shutdown or soft start function. It is inside pull high function. For normal application, the
pin must be connected a capacitor to ground. There is a 5μA current to charge this capacitor, vary the different
capacitor value to control soft start time. Allow the switching regulator circuit to be shutdown pulling this pin below
a 0.8V threshold voltage; the shutdown supply current is approximately 150μA
Inductor Selection
For most designs, the different frequency can be reducing the inductor value; The TS19378 is suggested 33μH.
Where is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high
ripple currents. Choose inductor ripple current approximately 20% of the maximum load current 2A, ΔIL=0.4A. The
DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to
prevent core saturation (2A+0.2A).
Input Capacitor Selection
This capacitor should be located close to the IC using short leads and the voltage rating should be approximately
1.5 times the maximum input voltage. The RMS current rating requirement for the input capacitor of a buck
regulator is approximately 1⁄2 the DC load current. A low ESR input capacitor sized for maximum RMS current
must be used. A 220µF low ESR capacitor for most applications is sufficient.
Over Voltage Protection
The OVP voltage is set by outside resistance (R1 and R4). The external resistor sets the OVP voltage according to
the following equation:
R
4
)
R
1
If V
OVP
>0.85V, The OVP is happened that to disable the driver until V
OVP
<0.85V.
V
OUT
(
OVP
)
=
V
OVP
×
(1
+
Output Capacitor Selection
For lower output voltage ripple and more stable LED current, higher value output capacitor and low ESR is
recommended. A 470µF electrolytic capacitor works for most of the applications.
Document Number: DS_P0000199
5
Version: B15
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