IS31LT3170 [ISSI]

10-TO-150MA CONSTANT-CURRENT LED DRIVER;


型号：	IS31LT3170
厂家：	INTEGRATED SILICON SOLUTION, INC
描述：	10-TO-150MA CONSTANT-CURRENT LED DRIVER 驱动
文件：	总9页 (文件大小：280K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

IS31LT3170/71

10-TO-150MA CONSTANT-CURRENT LED DRIVER

Advanced Information

July 2014

GENERAL DESCRIPTION

FEATURES

The IS31LT3170 and IS31LT3171 are adjustable

linear current devices with excellent temperature

stability. A single resistor is all that is required to set

the operating current from 10mA to 150mA. The

devices can operate from an input voltage from 2.8V

to 42V with a minimal voltage headroom of 0.264V.

Designed with a low dropout voltage; the device can

drive LED strings close to the supply voltage without

switch capacitors or inductors.



Low-side current sink

- Current preset to 10mA

- Adjustable from 10mA to 150mA with external

resistor selection



Wide input voltage range from

- 2.8V to 42V (IS31LT3171)

- 5V to 42V (IS31LT3170)

with a low dropout of 0.5V

The IS31LT3170/71 simplifies designs by

providing a stable current without the additional

requirement of input or output capacitors,

inductors, FETs or diodes. The complete constant

current driver requires only a current set resistor

and a small PCB area making designs both

efficient and cost effective.



Up to 10kHz PWM input (IS31LT3171 only)

Protection features:

- 0.2%/K negative temperature coefficient for-

thermal protection

- Open circuit and over voltage protection



Up to 1W power dissipation in a small SOT23-6

package

The EN Pin (1) of the IS31LT3171 can function as

the PWM signal input used for LED dimming

purposes.

RoHS compliant (Pb-free) package

APPLICATIONS

As a current sink it is ideal for LED lighting

applications or current limiter for power supplies.



Linear current sink

Current limiter for power supplies

LED signage

The device is provided in a lead (Pb) free, SOT23-6

package.

Retail lighting in refrigerator, freezer case and

vending machines



Instrumentation LED lighting

TYPICAL APPLICATION CIRCUIT

Figure 1 Typical Application Circuit

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170/71

PIN CONFIGURATION

Package

Pin Configuration (Top View)

SOT23-6

PIN DESCRIPTION

No.

Description

Enable pin (PWM input IS31LT3171 only).

Current sink.

2,3,5 OUT

GND

Ground.

REXT

Optional current adjust.

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170/71

ORDERING INFORMATION

Industrial Range: -40°C to +125°C

Order Part No.

Package

QTY/Reel

3000

IS31LT3170-STLS4-TR

IS31LT3171-STLS4-TR

SOT-23-6, Lead-free

time without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are

advised to obtain the latest version of this device specification before relying on any published information and before placing orders for products.

Integrated Silicon Solution, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the

product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not

authorized for use in such applications unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that:

a.) the risk of injury or damage has been minimized;

b.) the user assume all such risks; and

c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170/71

ABSOLUTE MAXIMUM RATINGS (Note 1)

Maximum enable voltage, V_EN(MAX)only for IS31LT3170-STLS4-TR

48V

V_EN(MAX)only for IS31LT3171-STLS4-TR

4.5V

Maximum output current, I_OUT(MAX)

Maximum output voltage, V_OUT(MAX)

Reverse voltage between all terminals, V_R

Junction to ambient, θ_JA

Power dissipation, P_D(MAX)(Note 2)

Maximum junction temperature, T_JMAX

Storage temperature range, T_STG

200mA

48V

0.5V

191°C/W

0.65W

150°C

-65°C ~ +150°C

−40°C ~ +125°C

Operating temperature range, T_A

ESD (HBM)

ESD (CDM)

Note 1:

TBD

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only

and functional operation of the device at these or any other condition beyond those indicated in the operational sections of the specifications is

not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Note 2:

Detail information please refer to package thermal de-rating curve on Page 7.

ELECTRICAL CHARACTERISTICS (TBD)

Test condition is T_A= 25°C, unless otherwise specified.

●

○

The symbol in the table means these parameters are only available for IS31LT3170-STLS4-TR.

The symbol in the table means these parameters are only available for IS31LT3171-STLS4-TR.

Symbol

Parameter

Condition

Min.

Typ.

Max. Unit

V_{BD_OUT}OUT pin breakdown voltage

V_EN= 0V

V_EN= 24V

V_EN= 3.3V

●

○

1.2

I_EN

Enable current

Internal resistor

Output current

R_INT

I_RINT= 10mA

83.5

106.5

Ω

V_OUT= 1.4V, V_EN= 24V

V_OUT= 1.4V, V_EN= 3.3V

●

○

●

○

I_OUT

V_OUT> 2.0V, V_EN= 24V

150

0.08

Output current at R_EXT= 5.1Ω

V_OUT> 2.0V, V_EN= 3.3V

I_OUT= 10mA

V_DROP

Voltage drop (V_REXT)

DC CHARACTERISTICS WITH STABILIZED LED LOAD (TBD)

Test condition is T_A= 25°C, unless otherwise specified.

●

○

The symbol in the table means these parameters are only available for IS31LT3170-STLS4-TR.

The symbol in the table means these parameters are only available for IS31LT3171-STLS4-TR.

Symbol

Parameter

Condition

Min.

Typ.

Max. Unit

Lowest sufficient supply voltage

overhead

V_SMIN

I_OUT> 18mA

V_OUT> 2.0V, V_EN= 24V

V_OUT> 2.0V, V_EN= 3.3V

●

○

●

○

-0.2

Output current change versus T_A

%/K

%/V

∆I_OUT/I_OUT

V_OUT> 2.0V, V_EN= 24V

Output current change versus

V_S

V_OUT> 2.0V, V_EN= 3.3V

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170/71

FUNCTIONAL BLOCK DIAGRAM

OUT

Current

Mirror

REXT

R_INT

GND

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170/71

TYPICAL PERFORMANCE CHARACTERISTICS (TBD)

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170/71

APPLICATIONS INFORMATION

IS31LT3170/71 provides an easy constant current

source solution for LED lighting applications. It uses

an external resistor to adjust the LED current from

10mA to 150mA. The LED current can be

determined by the Equation (1):

(2)

I_LED I_SET0.2%



T_A 25



When operating the chip at high ambient

temperatures, or when driving maximum load

current, care must be taken to avoid exceeding the

package power dissipation limits. Exceeding the

package dissipation will cause the device to enter

thermal protection mode. The maximum package

power dissipation can be calculated using the

following equation (3):

0.065



R_INT R_EXT



(1)

I_SET 15

R_INT R_EXT

Where R_INT(96.7Ω typ) is an internal resistor and

_EXTis the external resistor.

Paralleling a low tolerance resistor R_EXTwith the

internal resistor R_INTwill improve the overall

accuracy of the current sense resistance. The

resulting output current will vary slightly lower due to

the negative temperature coefficient (NTC) resulting

from the self heating of the IS31LT3170/71.

T_{J (MAX )} T_A

(3)

P_{D(MAX )}



_JA

Where T_J(MAX)is the maximum junction temperature,

T_Ais the ambient temperature, and θ_JAis the junction

to ambient thermal resistance; a metric for the

relative thermal performance of a package.

HIGH INPUT VOLTAGE APPLICATION

When driving a long string of LEDs whose total

forward voltage drop exceeds the IS31LT3170

The recommended maximum operating junction

temperature, T_J(MAX), is 150°C and so the maximum

ambient temperature is determined by the package

parameter; θ_JA. The θ_JAfor the IS31LT3170/71

SOT23-6 package, is 191°C/W.

V_{BD_OUT}limit of 42V, it is possible to stack several

LEDs(such as 2 LEDs) between the EN pin and the

OUT pins 2,3, and 5 so the voltage on the EN pin is

higher than 5V. The remaining string of LEDs can

then be placed between power supply +V_Sand EN

pin, (Figure 3). The number of LEDs required to

stack at EN pin will depend on the LED’s forward

voltage drop (VF) and the +V_Svalue.

Therefore the maximum power dissipation at T_A= -

40°C is:

150C  40C

191C /W

P_{D(MAX )}



 1W

The actual power dissipation P_Dis:

(4)

P_DV_OUT(I_EN I_OUT

)

To ensure the performance, the die temperature (T_J)

of the IS31LT3170/71 should not exceed 125°C. The

graph below gives details for the package power

derating.

Figure 3 High Input Voltage Application Circuit

1.2

SOT23-6

Note: when operating the IS31LT3170 at voltages

exceeding the device operating limits, care needs to

be taken to keep the EN pin and OUT pin voltage

below 42V.

0.8

0.6

0.4

THERMAL PROTECTION AND DISSIPATION

The IS31LT3170/71 implements thermal foldback

protection to reduce the LED current when the

package’s thermal dissipation is exceeded and

prevent “thermal runaway”. The thermal foldback

implements a negative temperature coefficient

(NTC) of -0.2%/K. The LED current can be

calculated by Equation (2):

0.2

-40 -25 -10

95 110 125

Temperature (°C)

Figure 4 P_Dvs. T_A(SOT23-6)

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170/71

CLASSIFICATION REFLOW PROFILES

Profile Feature

Pb-Free Assembly

Preheat & Soak

150°C

Temperature min (Tsmin)

200°C

Temperature max (Tsmax)

60-120 seconds

Time (Tsmin to Tsmax) (ts)

Average ramp-up rate (Tsmax to Tp)

Liquidous temperature (TL)

Time at liquidous (tL)

3°C/second max.

217°C

60-150 seconds

Max 260°C

Peak package body temperature (Tp)*

Time (tp)** within 5°C of the specified

classification temperature (Tc)

Average ramp-down rate (Tp to Tsmax)

Time 25°C to peak temperature

Max 30 seconds

6°C/second max.

8 minutes max.

Figure 5 Classification Profile

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170/71

PACKAGE INFORMATION

SOT23-6 (TBD)

Note: All dimensions in millimeters unless otherwise stated.

Integrated Silicon Solution, Inc. – www.issi.com

Rev. 00A, 05/20/2014

IS31LT3170 [ISSI]

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