TS19460

TS19460
AC/DC WLED Driver with Average-Mode
Constant Current Control
SOP-8
Pin Definition:
1. VIN
8. RT
2. CS
7. LD
3. GND
6. VDD
4. Gate
5. PWMD
General Description
The TS19460 is an average current mode control LED driver IC operating in a constant off-time mode. It greatly
improves accuracy, line and load regulation of the LED current without any need for loop compensation or highside current sensing. The output LED current accuracy is at ±5%, and it is equipped with current limit comparator
for hiccup mode output short circuit protection.
The TS19460 can be powered from an 8V~450V supply. A PWM dimming input is provided that accepts an
external control TTL compatible signal. The output current can be programmed by an internal 250mV reference,
or controlled externally through a 0~1.5V dimming input. The TS19460 is ideally suited for buck LED drivers and
is requires only few external components (apart from the power stage) to produce a controlled LED current
making it and ideal solution for low cost LED drivers.
Features
Ordering Information
●
Fast average current controller
●
Programmable constant off-time switching
●
Linear and PWM dimming capability
●
Requires few external components for operation
Note: “G” denote for Halogen Free Product
●
Output short circuit protection with skip mode
Typical Application Circuit
●
Pin –compatible with TS19450CS
Part No.
Package
Packing
TS19460CS RLG
SOP-8
2.5kpcs / 13” Reel
Application
●
DC/DC or AC/DC LED driver applications
●
RGB backlighting LED driver
●
Back lighting of flat panel displays
●
General purpose constant current source
●
Signage and decorative LED lighting
●
LED street lighting
Absolute Maximum Ratings
Parameter
Symbol
Limit
Unit
Input Voltage Range
VIN to GND
-0.5 ~ +470
V
Internal Regulated Voltage
VDD to GND
12
V
-0.3 ~ (VDD+0.3)
V
mW
CS, LD, PWMD, Gate, RT to GND
Continuous Power Dissipation
PD
650
Storage Temperature Range
TA
-65 to +150
o
C
TJ
-40 to +150
o
C
RθJA
128
Junction Temperature Range
Thermal Resistance – Junction to Ambient
o
C/W
Note: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the
device
1/7
Version: C13
TS19460
AC/DC WLED Driver with Average-Mode
Constant Current Control
Electrical Specifications (TA= 25oC, VIN= 12V, VLD=PWM=VDD, unless otherwise noted)
Function Parameter
Symbol
Test Conditions
Min
Typ
Max
Units
8.0
--
-0.5
450
1.0
V
mA
7.25
7.5
7.75
V
0
--
1.0
V
0
--
100
mV
6.45
6.7
6.95
V
--
500
--
mV
3.5
--
--
mA
Input
(1)
DC Input Voltage Range
Shut-down Mode Supply Current
VINDC
IINSD
DC input voltage
Pin PWMD to GND
Internal Regulator
Internally Regulated Voltage
VDD
Line Regulation of VDD
∆VDDLine
Load Regulation of VDD
∆VDDLoad
VIN=8V, IDD(EXT)=0
500pF at Gate, RT=226kΩ
VIN=8~450V, IDD(EXT)=0
500pF at Gate, RT=226kΩ
IDD(EXT)= 0 ~ 1mA
500pF at Gate, RT=226kΩ
VIN rising
Undervoltage Lockout Threshold
UVLO
Undervoltage Lockout Hysteresis
∆UVLO
VIN falling
Maximum Input Current
IIN (MAX)
VIN=8V
Dimming
PWMD Input Low Voltage
VENL
VIN=8V~450V
--
--
0.8
V
PWMD Input High Voltage
PWMD Pull-down resistance at
PWMD
VENH
VIN=8V~450V
2.0
--
--
V
REN
VPWMD=5V
50
100
150
kΩ
238
--
250
0.18
262
--
mV
mV
---
150
200
---
mV
mV
150
-32
----
280
1
48
ns
µs
---
12
--
Average Current Sense Logic
Current Sense Reference Voltage
LD to Current Sense Ratio
LD input Voltage Shutdown
LD input Voltage Enable
Current Sense Blanking Interval
Minimum On-Time
VCS
Av(LD)
VLD(OFF)
∆VLD(OFF)
TBLANK
TON(min)
VLD falling
VLD rising
VCS= VCS + 30mV
RT=1MΩ
Off Time
TOFF
Max. Steady-State Duty Cycle
DMAX
8
75
Hiccup Threshold Voltage
Current Limit Delay CS to Gate
VCS
TDELAY
VCS= VCS + 30mV
410
--
---
470
150
mV
ns
Short Circuit Hiccup Time
Minimum On-Time (Short Circuit)
THICCUP
TON(min)
VCS= VDD
330
--
---
460
430
µs
ns
Gate Sourcing Current
ISOURCE
VGATE=0V, VDD=7.5V
165
--
--
mA
Gate Sinking Current
Gate output Rise Time
ISINK
TRISE
VGATE=VDD, VDD=7.5V
CGATE=500pF, VDD=7.5V
165
--
-30
-50
mA
ns
--
30
50
ns
RT=226kΩ
µs
%
Short Circuit Protection
Gate Driver
Gate Output Fall Time
TFALL
CGATE=500pF, VDD=7.5V
Note:
1. Limited by package power dissipation, whichever is lower
2/7
Version: C13
TS19460
AC/DC WLED Driver with Average-Mode
Constant Current Control
Block Diagram
Pin Description
Pin
Function
1
VIN
2
CS
3
GND
4
GATE
5
PWMD
6
VDD
Description
This pin is the input of 8V~450V linear regulator
This pin is the current sense pin used to sense the MOSFET current by means of an
external sense resistor.
Ground return for all internal circuitry. This pin must be electrically connected to the
ground of the power train.
This pin is the output GATE driver for an external N-CH Power MOSFET
This is the PWM dimming input of the IC. When this pin is pulled to GND, the Gate Driver
is turned off. When the pin is pulled high, the GATE driver operates normally.
This is the power supply pin for all internal circuits.
It must be bypassed with a low ESR capacitor to GND (≥0.1µF)
This pin is the linear dimming input and sets the current sense threshold as long as the
7
LD
voltage at the pin is less than 1.5V, The Gate output is disable when LD voltage
<150mV(typ.) and recovery when LD voltage >200mV (typ.)
8
RT
A resistor is connected between RT and GND to program the Gate off-time.
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Version: C13
TS19460
AC/DC WLED Driver with Average-Mode
Constant Current Control
Application Information
The TS19460 is optimized to drive buck LED drivers using average current mode control. This method of control
enables fairly accurate LED current control without the need for high side current sensing or the design of any
closed loop controllers. The IC uses very few external components and enables both linear and PWM dimming of
the LED current.
A resistor connected to the RT pin programs the off-time. Constant off-time control average current mode is used
for stability and to improve the LED current regulation over a wide range of input voltages.
The current through the switching MOSFET source is averaged and used to give constant-current feedback. This
current is detected from a sense resistor at the CS pin, the feedback operates in a fast open-loop mode, there is no
compensation required, the output current is programmed as
ILED = 0.25V / RCS
When the Voltage at the LD input >1.5V, otherwise
ILED = ( VLD * 0.181 ) / RCS
When application to design the inductor witching ripple current in it is 40% of average peak to peak, full load
current, the inductance can be calculated as follow:
LOUT = ( VOUT(max) * TOFF ) / ( 0.4 * IOUT )
The duty cycle range of current control feedback is limited to duty <75%, A reduction in the LED current string
voltage is greater than 75% of input voltage.
Reducing the output LED voltage is below VOUT(MIN) = VIN * D(MIN), where D(MIN) = 1uS / (TOFF + 1uS), may also
result in the loss of regulation of LED current. This condition will cause an increase in the LED current and can be
possible to trip the short circuit protection comparator.
The short circuit protection comparator trips when the voltage at CS exceeds 0.44V, the Gate off time (THICCUP =
400uS) is generated to prevent stair-casing of inductor current and potentially its saturation due to insufficient
output voltage.
The leading edge blanking delay is provide at CS to prevent false triggering of current feedback and short circuit
protection.
Input Voltage Regulator
The TS19460 can be powered directly from its VIN pin and can work from 8.0V~450VDC at its VIN pin. When a
voltage is applied at the VIN pin, the TS19460 maintains a constant 7.5V at the VDD pin. This voltage is used to
power the IC and any external resistor dividers needed to control the IC. The VDD pin must be bypassed by a low
ESR capacitor to provide a low impedance path for the high frequency current of the output GATE driver. The
TS19460 can be also operated by supplying a voltage at the VDD pin greater than the internally regulated voltage.
Please note that this external voltage at the VDD pin should not exceed 12V.
Although the VIN pin of the TS19460 is rated up to 450V, the actual maximum voltage that can be applied is limited
by the power dissipation in the IC. For example, if an SOP-8 (junction to ambient thermal resistance RθJA = 128°C/
W) TS19460 draws about IIN = 2.0mA from the VIN pin, and has a maximum allowable temperature rise of the
junction temperature limited to about the maximum voltage at the VIN pin would be:
VIN(MAX) = ( TJ(MAX) – TA ) / ( RθJA * IIN ) = 390V
In these cases, to operate the TS19460 from higher input voltages, a Zener diode can be added in series with the
VIN pin to divert some of the power loss from the TS19460 to the Zener diode. In the above example, using a 100V
zener diode will allow the circuit to easily work up to 490V.
4/7
Version: C13
TS19460
AC/DC WLED Driver with Average-Mode
Constant Current Control
Application Information (Continue)
The input current drawn from the VIN pin is a sum of the 1.0mA current drawn by the internal circuit and the current
drawn by the GATE driver (which in turn depends on the switching frequency and the GATE charge of the external
IIN ≈ 1mA + QG x fS
In the above equation, fS is the switching frequency and QG is the GATE charge of the external MOSFET (which
can be obtained from the datasheet of the MOSFET).
Oscillator
The oscillator in the TS19460 is controlled by a single resistor connected at the RT pin. The equation governing the
off-time of the GATE output is given by:
TOFF(uS) = ( RT(KΩ) / 25 ) + 0.3
*within the range of 30kΩ ≤ RT ≤ 1MΩ
Linear Dimming
The Linear Dimming pin is used to control the LED current, when voltage at LD is fall below 1.5V, the internal
reference voltage (250mV) to the constant current feedback become over ridden by VLD * 0.181, and the current in
the inductor remain continuous, the LED current is given by ILED = ( VLD * 0.181 ) / RCS, The Gate output is disable
when LD voltage <150mV(typ.) and recovery when LD voltage >200mV (typ.)
The Linear Dimming input could also be used for mixed-mode dimming to expand the dimming ratio, in this kind of
application condition, the pulse-width modulated signal of a measured amplitude below 1.5V should be applied at
LD.
PWM Dimming
PWM Dimming can be achieved by driving the PWMD pin with a square wave signal. The rising and falling edges
are limited by current slew rate in inductor, the first switching cycle is terminated upon reaching the level (250mV)
at CS, the circuit is further reaching its steady state within 3~5 switching cycle regardless of the switching
frequency.
5/7
Version: C13
TS19460
AC/DC WLED Driver with Average-Mode
Constant Current Control
SOP-8 Mechanical Drawing
Unit: Millimeters
Marking Diagram
Y = Year Code
M = Month Code for Halogen Free Product
(O=Jan, P=Feb, Q=Mar, R=Apl, S=May, T=Jun, U=Jul, V=Aug, W=Sep,
X=Oct, Y=Nov, Z=Dec)
L = Lot Code
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Version: C13
TS19460
AC/DC WLED Driver with Average-Mode
Constant Current Control
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: C13