TS19450CSRL [TSC]

AC/DC WLED Driver with External MOSFET Universal High Brightness; AC / DC WLED驱动器，外置MOSFET通用高亮度


型号：	TS19450CSRL
厂家：	TAIWAN SEMICONDUCTOR COMPANY, LTD
描述：	AC/DC WLED Driver with External MOSFET Universal High Brightness AC / DC WLED驱动器，外置MOSFET通用高亮度驱动器接口集成电路光电二极管
文件：	总8页 (文件大小：393K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

TS19450

AC/DC WLED Driver with External MOSFET

Universal High Brightness

SOP-8

Pin Definition:

1. VIN

8. RT

2. CS

7. LD

3. GND

4. Gate

6. VDD

5. PWMD

General Description

The TS19450 is an open loop, current mode control LED driver IC. It can be programmed to operate in either a

constant frequency or constant off-time mode. It includes an 8V~450V linear regulator which allows it to work from a

wide range of input voltages without the need for an external low voltage supply. The TS19450 includes a PWM

dimming input that can accept an external control signal with a duty ratio of 0~100% and a frequency of up to a few

kHz. It also includes a 0~250mV linear dimming input which can be used for linear dimming of the LED current.

The TS19450 is ideally suited for buck LED drivers. Since it operates in open loop current mode control, the controller

achieves good output current regulation without the need for any loop compensation. PWM dimming response is

limited only by the rate of rise and fall of the inductor current, enabling very fast rise and fall times. The TS19450

requires only free 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

●

Switch mode controller for single switch LED drivers

Part No.

Package

SOP-8

Packing

Open loop peak current controller

TS19450CS RL

2.5Kpcs / 13” Reel

Internal 8V~450V linear regulator

Constant frequency or constant off-time operation

Linear and PWM dimming capability

Typical Application Circuit

Requires few external components for operation

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

Charger

Absolute Maximum Rating

Parameter

Symbol

V_INto GND

V_DDto GND

Limit

-0.5 ~ +470

13.5

Unit

Input Voltage Range

Internal Regulated Voltage

CS, LD, PWMD, Gate, RT to GND

Continuous Power Dissipation

Storage Temperature Range

Junction Temperature Range

Thermal Resistance – Junction to Ambient

-0.3 ~ (V_DD+0.3)

630

P_D

T_A

^oC

-65 to +150

-40 to +150

128

T_J

Rθ_JA

^oC/W

1/8

Version: A10

TS19450

AC/DC WLED Driver with External MOSFET

Universal High Brightness

Electrical Specifications (T_A= 25^oC, V_IN= 12V, unless otherwise noted)

Function Parameter

Input

Symbol

Test Conditions

Min Typ Max Units

DC Input Voltage Range

V_INDC

I_INSD

DC input voltage

8.0

450

1.0

Shut-down Mode Supply Current

Pin PWMD to GND

0.5

Internal Regulator

V_IN=8V, I_DD(EXT)=0, 500pF at

Gate, R_T=226kΩ, PWMD=V_DD

V_IN=8~450V, I_DD(EXT)=0, 500pF at

Gate, R_T=226kΩ, PWMD=V_DD

I_DD(EXT)=0~1mA, 500pF at Gate,

R_T=226kΩ, PWMD=V_DD

Internally Regulated Voltage

Line Regulation of V_DD

Load Regulation of V_DD

V_DD

7.0

7.5

8.0

1.0

∆V_DDLine

∆V_DDLoad

100

Undervoltage Lockout Threshold

Undervoltage Lockout Hysteresis

UVLO

V_DDrising

V_DDfalling

6.45

6.7

6.95

∆UVLO

500

VDD current available for external

circuitry

V_{DD (EXT)}

V_IN=8V~100V

1.0

Dimming

PWMD Input Low Voltage

PWMD Input High Voltage

V_ENL

V_ENH

V_IN=8V~450V

1.0

2.4

PWMD Pull-down resistance at

PWMD

R_EN

V_LD

V_PWMD=5V

V_IN=12V

100

150

250

kΩ

Linear Dimming pin voltage

Current Sense Comparator

-40ºC < T_A< +85ºC

T_A< +125ºC

225

213

-12

250

275

287

Current Sense Pull-in Threshold

Voltage

V_CSTH

Offset Voltage for LD Comparator

Current Sense Blanking Interval

V_OFFSET

T_BLANK

V_LD=V_DD, V_CS=0.55V_LD

150

215

280

V_IN=12V, V_LD=0.15V,

V_CS=0~0.22V after T_BLANK

Delay to Output

T_DELAY

300

Oscillator

R_T=1MΩ

100

Oscillator Frequency

f_OSC

kHz

R_T=223kΩ

120

100

Max. Oscillator PWM Duty Cycle

Gate Driver

D_MAX

F=25kHz at Gate, CS to GND

Gate Sourcing Current

I_SOURCE

I_SINK

V_GATE=0V, V_DD=7.5V

V_GATE=V_DD, V_DD=7.5V

I_OUT=-10mA

165

Gate Sinking Current

V_DD

Gate high output voltage

V_GATE(HI)

V_DD

0.3

Gate low output voltage

Gate output Rise Time

Gate Output Fall Time

V_GATE(LO)

T_RISE

I_OUT=10mA

0.3

C_GATE=500pF, 10%~90% V_GATE

C_GATE=500pF, 90%~10% V_GATE

T_FALL

Note 1: Limited by package power dissipation, whichever is lower

Note 2: V_DDload current external to the TS19450

Note 3: Denotes the specifications which apply over the full operating ambient temperature range of -40ºC<T_A<+125ºC

2/8

Version: A10

TS19450

AC/DC WLED Driver with External MOSFET

Universal High Brightness

Block Diagram

ꢀ

Pin Description

Function

Description

VIN

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. When this pin exceeds the low of either the internal 250mV

or the voltage at the LD pin, the GATE output goes low

Ground return for all internal circuitry. This pin must be electrically connected to the

ground of the power train.

GND

GATE

PWMD

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.

VDD

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 voltage at the pin is less than 250mV (typ.)

This pin sets the oscillator frequency. When a resistor is connected between RT and

GND, the IC operates in constant frequency mode. When the resistor is connected

between RT and GATE, the IC operates in constant off-time mode.

3/8

Version: A10

TS19450

AC/DC WLED Driver with External MOSFET

Universal High Brightness

Application Information

The TS19450 is optimized to drive buck LED drivers using open-loop peak 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 frequency of operation (or the off-time). The oscillator produces

pulses at regular intervals. These pulses set the SR ﬂip-ﬂop in the TS19450 which causes the GATE driver to turn on.

The same pulses also start the blanking timer which inhibits the reset input of the SR ﬂip ﬂop and prevent false turn-

offs due to the turn-on spike. When the FET turns on, the current through the inductor starts ramping up. This current

ﬂows through the external sense resistor R_CSand produces a ramp voltage at the CS pin. The comparators are

constantly comparing the CS pin voltage to both the voltage at the LD pin and the internal 250mV. Once the blanking

timer is complete, the output of these comparators is allowed to reset the ﬂip ﬂop. When the output of either one of the

two comparators goes high, the ﬂip ﬂop is reset and the GATE output goes low. The GATE goes low until the SR ﬂip

ﬂop is set by the oscillator. Assuming a 30% ripple in the inductor, the current sense resistor R_CScan be set using:

Constant frequency peak current mode control has an inherent disadvantage – at duty cycles greater than 0.5, the

control scheme goes into sub harmonic oscillations. To prevent this, an artiﬁcial slope is typically added to the current

sense waveform. This slope compensation scheme will affect the accuracy of the LED current in the present form.

However, a constant off-time peak current control scheme does not have this problem and can easily operate at duty

cycles greater then 0.5 and also gives inherent input voltage rejection making the LED current almost insensitive to

input voltage variations. But, it leads to variable frequency operation and the frequency range depends greatly on the

input and output voltage variation. TS19450 makes it easy to switch between the two modes of operation by changing

one connection (see oscillator section).

Input Voltage Regulator

The TS19450 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 TS19450 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 TS19450 can be also operated by supplying a voltage at the VDD pin greater than the internally regulated voltage.

This will turn off the internal linear regulator of the IC and the TS19450 will operate directly off the voltage supplied at

the VDD pin. Please note that this external voltage at the VDD pin should not exceed 12V.

Although the VIN pin of the TS19450 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 Rθ_JA= 128°C/ W)

TS19450 draws about I_IN= 2.0mA from the VIN pin, and has a maximum allowable temperature rise of the junction

temperature limited to about ∆T=10ºCm the maximum voltage at the VIN pin would be:

In these cases, to operate the TS19450 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 TS19450 to the Zener diode. In the above example, using a 100V zener

diode will allow the circuit to easily work up to 450V.

4/8

Version: A10

TS19450

AC/DC WLED Driver with External MOSFET

Universal High Brightness

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

In the above equation, f_Sis the switching frequency and Q_Gis the GATE charge of the external MOSFET (which can be

obtained from the datasheet of the MOSFET).

Current Sense

The current sense input of the TS19450 goes to the non-inverting inputs of two comparators. The inverting terminal of

one comparator is tied to an internal 250mV reference whereas the inverting terminal of the other comparator is

connected to the LD pin. The outputs of both these comparators are fed into an OR GATE and the output of the OR

GATE is fed into the reset pin of the ﬂip-ﬂop. Thus, the comparator which has the lowest voltage at the inverting

terminal determines when the GATE output is turned off.

The outputs of the comparators also include a 150~280ns blanking time which prevents spurious turn-offs of the exter-

nal MOSFET due to the turn-on spike normally present in peak current mode control. In rare cases, this internal

blanking might not be enough to ﬁlter out the turn-on spike. In these cases, an external RC ﬁlter needs to be added

between the external sense resistor (R_CS) and the CS pin.

Please note that the comparators are fast (with a typical 80ns response time). Hence these comparators are more

susceptible to be triggered by noise than the comparators of the TS19450. A proper layout minimizing external induc-

tances will prevent false triggering of these comparators.

Oscillator

The oscillator in the TS19450 is controlled by a single resistor connected at the RT pin. The equation governing the

oscillator time period t_OSCis given by:

If the resistor is connected between RT and GND, TS19450 operates in a constant frequency mode and the above

equation determines the time-period. If the resistor is connected between RT and GATE, the TS19450 operates in a

constant off-time mode and the above equation determines the off-time.

Linear Dimming

The Linear Dimming pin is used to control the LED current. There are two cases when it may be necessary to use the

Linear Dimming pin.

* In some cases, it may not be possible to ﬁnd the exact value required to obtain the LED current when the R_CS

internal 250mV is used. In these cases, an external voltage divider from the VDD pin can be connected to the LD pin

to obtain a voltage (less than 250mV) corresponding to the desired voltage across R_CS.

* Linear dimming may be desired to adjust the current level to reduce the intensity of the LEDs. In these cases, an

external 0~250mV voltage can be connected to the LD pin to adjust the LED current during operation.

To use the internal 250mV, the LD pin can be connected to VDD.

Note:

Although the LD pin can be pulled to GND, the output current will not go to zero. This is due to the presence of a mini-

mum on-time (which is equal to the sum of the blanking time and the delay to output time) which is about 450ns. This

will cause the MOSFET to be on for a minimum of 450ns and thus the LED current when LD = GND will not be zero.

This current is also dependent on the input voltage, inductance value, forward voltage of the LEDs and circuit parasitic.

To get zero LED current, the PWMD pin has to be used.

5/8

Version: A10

TS19450

AC/DC WLED Driver with External MOSFET

Universal High Brightness

Application Information (Continue)

PWM Dimming

PWM Dimming can be achieved by driving the PWMD pin with a low frequency square wave signal. When the PWM

signal is zero, the GATE driver is turned off and when the PWMD signal if high, the GATE driver is enabled. Since the

PWMD signal does not turn off the other parts of the IC, the response of the TS19450 to the PWMD signal is almost

instantaneous. The rate of rise and fall of the LED current is thus determined solely by the rise and fall times of the

inductor current.

To disable PWM dimming and enable the TS19450 permanently, connect the PWMD pin to VDD

ꢀ

6/8

Version: A10

TS19450

AC/DC WLED Driver with External MOSFET

Universal High Brightness

SOP-8 Mechanical Drawing

SOP-8 DIMENSION

MILLIMETERS

INCHES

MIN

DIM

MIN

4.80

3.80

1.35

0.35

0.40

MAX

5.00

4.00

1.75

0.49

1.25

MAX.

0.196

0.157

0.068

0.019

0.049

0.189

0.150

0.054

0.014

0.016

1.27BSC

0.05BSC

0.10

0º

0.25

7º

0.004

0º

0.009

7º

5.80

0.25

6.20

0.50

0.229

0.010

0.244

0.019

Marking Diagram

Y = Year Code

M = Month Code

(A=Jan, B=Feb, C=Mar, D=Apl, E=May, F=Jun, G=Jul, H=Aug, I=Sep,

J=Oct, K=Nov, L=Dec)

L = Lot Code

7/8

Version: A10

TS19450

AC/DC WLED Driver with External MOSFET

Universal High Brightness

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.

8/8

Version: A10

TS19450CSRL [TSC]

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