TS19376 [TSC]
1A Step-down High Brightness LED Driver; 1A降压型高亮度LED驱动器
| 型号： | TS19376 |
| 厂家： | 
TAIWAN SEMICONDUCTOR COMPANY, LTD |
| 描述： | 1A Step-down High Brightness LED Driver |
| 文件： | 总8页 (文件大小：152K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
TS19376
1A Step-down High Brightness LED Driver
SOT-89-5L
Pin Definition:
1. SW
2. GND
3. DIM
4. CSN
5. VIN
General Description
The TS19376 is a continuous conduction mode inductive step-down converter, designed for driving single or
multiple series connected LED efficiently from a voltage source higher than the total LED chain voltage. The
device operates from an input supply between 8V and 32V and provides an externally adjustable output current of
up to 1A. Depending upon the supply voltage and external components, the TS19376 can provide more than 15
watts of output power. The TS19376 includes the power switch and a high-side output current sensing circuit,
which uses an external resistor to set the nominal average output current, and a dedicated DIM input accepts a
wide range of pulsed dimming. Applying a voltage of 0.3V or lower to the DIM pin turns the output off and switches
the device into a low current standby state
Features
Application
●
●
●
●
●
●
●
●
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Wide input voltage range: 8V to 32V
●
●
●
White LED Backlighting
Up to 1A output current
High Power LED Application
LED Lighting Equipment
5000:1 Dimming
Single pin on/off and brightness control using PWM
Up to 1MHz switching frequency
Typical 5% output current accuracy
High-Side Current Sense
Ordering Information
Part No.
Package
Packing
TS19376CY5 RMG SOT-89-5L
1Kpcs / 7” Reel
Hysteretic Control: No Compensation
Adjustable Constant LED Current
Note: “G” denotes Halogen Free Product.
Absolute Maximum Rating
Parameter
Symbol
Limit
Unit
Supply Voltage
VIN
SW
CSN
DIM
ISW
-0.3 to 40
-0.3 to 40
+0.3 to (-6.0)
-0.3 to +6
1.0
V
V
Driver output Voltage
Current sense input (Respect to VIN)
Logic level dimming input
V
V
Switch output current
A
Power Dissipation
PDMAX
TJ
1.5
W
Operation Junction Temperature Range
Storage Temperature
-40 to 125
-55 to 150
15
°C
TSTG
θJC
°C
Thermal Resistance from Junction to case
°C/W
Thermal Resistance from Junction to ambient
θJA
50
°C/W
Note: θJA is measured with the PCB copper area (need connect to Exposed Pad) of approximately 1 in2(Multi-layer).
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Version: A12
TS19376
1A Step-down High Brightness LED Driver
Electrical Specifications (VIN=12V, TA =25oC, unless otherwise noted)
Characteristics
Symbol
Conditions
Min
8
Typ
--
Max
32
--
Units
V
Input voltage
VIN
Under voltage lock out
UVLO Hysterisis
VUVLO
VIN rising
--
7
V
VUVLO_hys VIN falling
FSW
--
1000
--
--
mV
MHZ
Max. Switching Frequency
Current Sense
--
1
Mean current sense threshold voltage
Sense threshold hysteresis
CSN Pin Input Current
DIM Input
VCSN
VCSN_hys
ICSN
VIN–VCSN
120
--
130
±15
0.5
140
--
mV
%
VIN–VCSN = 50mV
--
--
µA
DIM input voltage High
DIM input voltage Low
Max. DIM Frequency
VDIM_H
VDIM_L
fDIM
2.0
--
--
--
--
0.3
50
1
V
V
fOSC = 500kHz
fDIM = 100Hz
--
--
kHZ
Duty cycle range of low frequency dimming
Brightness control range
Duty cycle range of high frequency dimming
Brightness control range
DIM pull up resistor to Internal
supply voltage
0.02%
--
--
DPWM_LF
5000:1
--
--
fDIM = 20kHz
4%
--
1
DPWM_HF
25:1
--
RDIM
--
--
300
70
--
--
KΩ
µA
DIM input leakage low
Output Switch
IDIM_L
VDIM = 0
Saturation Voltage
VSAT
VSAT
IOUT = 0.3A
IOUT = 0.8A
--
--
--
--
0.8
1.0
--
1.0
1.2
1.0
5
V
V
Saturation Voltage
Continuous SW Current
SW Leakage Current
ISWmean
ILEAK
A
0.5
µA
Thermal Shutdown
Thermal Shutdown Threshold
Thermal Shutdown hysteresis
TSD
--
--
150
35
--
--
°C
°C
TSD-hys
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Version: A12
TS19376
1A Step-down High Brightness LED Driver
Block Diagram
V25
VIN
SW
CS
COMPARATOR
-
+
CSN
130mV
2.5V
GATE
DRIVER
Driver
-
+
70µ
UVLO
COMPARATOR
GND
DIM
BUFFER
DIM
Pin Function Description:
Pin
1
2
Name
SW
GND
Description
Switch Output. SW is the output of the internal driver switch.
Signal and power ground. Connect directly to ground plane.
Logic level dimming input. Drive DIM low to turn off the current regulator.
Drive DIM high to enable the current regulator.
Current sense input
3
DIM
4
5
CSN
VIN
Input Supply Pin. Must be locally bypassed.
Typical Application Circuit
VCSN
RS
0.130
0.4
ILED
=
=
= 0.325A
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Version: A12
TS19376
1A Step-down High Brightness LED Driver
Application Information
Operation Description
The device, in conjunction with the coil (L1) and current sense resistor (RS), forms a self oscillating continuous-
mode buck converter.
When input voltage VIN is first applied, the initial current in L1 and RS is zero and there is no output from the current
sense circuit. Under this condition, the output of CS comparator is high. This turns on an internal switch and
switches the SW pin low, causing current to flow from VIN to ground, via RS, L1 and the LED(s). The current rises at
a rate determined by VIN and L1 to produce a voltage ramp (VCSN) across RS. When (VIN-VCSN) > 150mV, the output
of CS comparator switches low and the switch turns off. The current flowing on the RS decreases at another rate.
When (VIN-VCSN) < 110mV, the switch turns on again and the mean current on the LED is determined by
110 + 150
(
mV) / RS= 130mV / RS.
2
The high-side current-sensing scheme and on-board current-setting circuitry minimize the number of external
components while delivering LED current with ±5% accuracy, using a 1% sense resistor.
The TS19376 allow dimming with a PWM signal at the DIM input. A logic level below 0.3V at DIM forces TS19376
to turn off the LED and the logic level at DIM must be at least 2.0V to turn on the full LED current. The frequency of
PWM dimming ranges from 100Hz to more than 20 kHz.
The DIM pin is pulled high current approximately 70µA. It can be floated at normal working. When a voltage applied
to DIM falls below the threshold (0.3V nom.), the output switch is turned off. The internal regulator and voltage
reference remain powered during shutdown to provide the reference for the shutdown circuit.
Additionally, to ensure the reliability, the TS19376 is built with a thermal shutdown (TSD) protection and a thermal
pad. The TSD protests the IC from over temperature (150°C). Also the thermal pad enhances power dissip ation. As
a result, the TS19376 can handle a large amount of current safely.
Setting nominal average output current with external resistor RS
The nominal average output current in the LED(s) is determined by the value of the external current sense resistor
(RS) connected between VIN and CSN and is given by:
IOUT = 0.130/RS (RS ≧ 0.16Ω)
This equation is valid when DIM pin is float. Actually, RS sets the maximum average current which can be adjusted
to a less one by dimming.
Output current adjustment by PWM control
A Pulse Width Modulated (PWM) signal with duty cycle PWM can be applied to the DIM pin, as shown below, to
adjust the output current to a value below the nominal average value set by resistor RS:
0.1×D
IOUT
=
RS
(0≦D≦100%, 0.3V＜Vpulse＜2.5V)
PWM dimming provides reduced brightness by modulating the LED’s forward current between 0% and 100%. The
LED brightness is controlled by adjusting the relative ratios of the on time to the off time. A 25% brightness level is
achieved by turning the LED on at full current for 25% of one cycle. To ensure this switching process between on
and off state is invisible by human eyes, the switching frequency must be greater than 100 Hz. Above 100 Hz, the
human eyes average the on and off times, seeing only an effective brightness that is proportional to the LED’s on-
time duty cycle. The advantage of PWM dimming is that the forward current is always constant; therefore the LED
color does not vary with brightness as it does with analog dimming. Pulsing the current provides precise brightness
control while preserving the color purity. The dimming frequency of TS19376 can be as high as 20 kHz.
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Version: A12
TS19376
1A Step-down High Brightness LED Driver
Application Information (Continue)
Shutdown mode
Taking the DIM pin to a voltage below 0.3V will turn off the output and the supply current will fall to a low standby
level of 70µA nominal.
Capacitor selection
A low ESR capacitor should be used for input decoupling, as the ESR of this capacitor appears in series with the
supply source impedance and lowers overall efficiency. This capacitor has to supply the relatively high peak current
to the coil and smooth the current ripple on the input supply. A minimum value of 4.7uF is acceptable if the input
source is close to the device, but higher values will improve performance at lower input voltages, especially when
the source impedance is high. The input capacitor should be placed as close as possible to the IC.
For maximum stability over temperature and voltage, capacitors with X7R, X5R, or better dielectric are
recommended. Capacitors with Y5V dielectric are not suitable for decoupling in this application and should not be
used.
Inductor selection
Recommended inductor values for the TS19376 are in the range 47uH to 120uH.
Higher values of inductance are recommended at lower output current in order to minimize errors due to switching
delays, which result in increased ripple and lower efficiency. Higher values of inductance also result in a smaller
change in output current over the supply voltage range. The inductor should be mounted as close to the device as
possible with low resistance connections to the SW and VIN pins.
Diode selection
For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance Schottky diode with
low reverse leakage at the maximum operating voltage and temperature. They also provide better efficiency than
silicon diodes, due to a combination of lower forward voltage and reduced recovery time.
It is important to select parts with a peak current rating above the peak coil current and a continuous current rating
higher than the maximum output load current. It is very important to consider the reverse leakage of the diode
when operating above 85°C. Excess leakage will incr ease the power dissipation in the device and if close to the
load may create a thermal runaway condition.
The higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak
voltage on the SW output. If a silicon diode is used, care should be taken to ensure that the total voltage appearing
on the SW pin including supply ripple, does not exceed the specified maximum value.
Reducing output ripple
Peak to peak ripple current in the LED(s) can be reduced, if required, by shunting a capacitor CLED across the
LED(s) as shown below:
A value of 1uF will reduce the supply ripple current by a factor three (approx.). Proportionally lower ripple can be
achieved with higher capacitor values. Note that the capacitor will not affect operating frequency or efficiency, but it
will increase start-up delay and reduce the frequency of dimming, by reducing the rate of rise of LED voltage.
By adding this capacitor the current waveform through the LED(s) changes from a triangular ramp to a more
sinusoidal version without altering the mean current value.
5/8
Version: A12
TS19376
1A Step-down High Brightness LED Driver
Application Information (Continue)
Operation at low supply voltage
The internal regulator disables the drive to the switch until the supply has risen above the startup threshold
(VUVLO). Above this threshold, the device will start to for this reason, the temperature coefficients of the operating.
However, with the supply voltage below the specified minimum value, the switch duty cycle will be high and the
device power dissipation will be at a maximum. Care should be taken to avoid operating the device under such
conditions in the application, in order to minimize the risk of exceeding the maximum allowed die temperature. (See
next section on thermal considerations). The drive to the switch is turned off when the supply voltage falls below
the under-voltage threshold (VUVLO-1V).
This prevents the switch working with excessive 'on' resistance under conditions where the duty cycle is high.
Thermal shutdown protection
To ensure the reliability, the TS19376 is built with a thermal shutdown (TSD) protection function. The TSD protests
the IC from over temperature (150°C). When the chip temperature decreases (115°C), the IC recovers aga in.
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Version: A12
TS19376
1A Step-down High Brightness LED Driver
SOT-89-5L Mechanical Drawing
SOT-89-5L DIMENSION
MILLIMETERS INCHES
DIM
MIN
4.40
4.05
1.50
0.35
2.40
0.80
MAX
4.60
4.25
1.70
0.41
2.60
--
MIN
0.17
0.16
0.06
0.01
0.09
0.03
MAX
0.18
0.17
0.07
0.02
0.10
--
A
B
C
D
E
F
G
H
I
3.00(typ)
1.50(typ)
0.12(typ)
0.06(typ)
0.40
1.40
0.52
1.60
0.01
0.05
0.02
0.06
J
7/8
Version: A12
TS19376
1A Step-down High Brightness LED Driver
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.
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Version: A12
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