ST STCS05A User Manual

0.5 A max constant current LED driver

Features

■ Up to 40 V input voltage

■ Less than 0.5 V voltage overhead

■ Up to 0.5 A output current

■ PWM dimming pin

■ Shutdown pin

■ LED disconnection diagnostic

■ Slope control with external cap

Applications

■ LED constant current supplying for varying

input voltages

■ Low voltage lighting

■ Small appliances LED lighting

■ Car LED lights

Description

The STCS05A is a BiCMOS constant current
source designed to provide a precise constant
current starting from a varying input voltage
source. The main target is to replace discrete

STCS05A

SO-8

components solution for driving LEDs in low
voltage applications such as 5 V, 12 V or 24 V
giving benefits in terms of precision, integration
and reliability.

The current is set with external resistor up to 0.5
A with a ± 10 % precision; a dedicated pin allows
implementing PWM dimming. An external
capacitor allows setting the slope for the current
rise from tens of microseconds to tens of
milliseconds allowing reduction of EMI.

An open-drain pin output provides information on
load disconnection condition.

Table 1. Device summary

Order code Package Packaging

STCS05ADR SO-8 2500 parts per reel

July 2008 Rev 2 1/18

www.st.com

18

Contents STCS05A

Contents

1 Application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

6 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

7 Detail description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7.1 Current setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7.2 Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7.3 PWM dimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7.4 Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

8 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

8.1 Reverse polarity protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

8.2 Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

9 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

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STCS05A Application diagram

1 Application diagram

Figure 1. Typical application diagram for 0.5 A LED current

V

V

IN

IN

4.5V to 40V

4.5V to 40V

BAT46ZFILM

BAT46ZFILM

RIN100 ohm

RIN100 ohm

OFF

OFF

OFF

OFF

C

C

BYP

BYP

0.1µF

0.1µF

ON

ON

ON

ON

Load disconnection

Load disconnection
(Open Drain output)

(Open Drain output)

V

V

PWM

PWM

EN

EN

CC

CC

DISC

DISC

STCS05A

STCS05A

C

C

SLOPE

SLOPE

10nF

10nF

DRAIN

DRAIN

C

C

DRAIN

DRAIN

0.47µF

0.47µF

FB

FB

GNDSLOPE

GNDSLOPE

R

R

FB

FB

0.2 ohm

0.2 ohm

3/18

Pin configuration STCS05A

2 Pin configuration

Figure 2. Pin connections (top view)

Table 2. Pin description

Pin n° Symbol Note

1V

2 PWM PWM dimming input

3 EN Shutdown pin

4 DRAIN Internal N-MOSFET drain

5FB

6 GND Ground

7 SLOPE Capacitor for slope control

8 DISC Load disconnection flag (open drain)

CC

Supply voltage

Feedback input. The control loop regulates the current in such a way that the average
voltage at the FB input is 100 mV (nominal). The cathode of the LED and a resistor to
ground to set the LED current should be connected at this point.

4/18

STCS05A Maximum ratings

3 Maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit

V

CC

DC supply voltage -0.3 to +45

V

DRAIN Drain pin -0.3 to +45

PWM, EN, DISC Logic pins -0.3 to + V

+ 0.3 V

CC

SLOPE, FB Configuration pins -0.3 to + 3.3 V

ESD Human body model (all pins) ±2 kV

(1)

Power Dissipation SO-8 T

T

J

T

STG

1. See Figure 16 for details of max power dissipation for ambient temperature higher than 25 °C

Junction temperature -40 to 150 °C

Storage temperature range -55 to 150 °C

=25°C

A

0.85 W

Note: Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these conditions is not implied.

Table 4. Thermal data

Symbol Parameter SO-8 Unit

R

thJC

R

thJA

1. This value depends from thermal design of PCB on which the device is mounted.

Thermal resistance junction-case 20 °C/W

Thermal resistance junction-ambient

(1)

100 °C/W

5/18

Electrical characteristics STCS05A

4 Electrical characteristics

Table 5. Electrical characteristics (V

C

DRAIN

= 1 µF; C

= 100 nF typical values are at TA = 25 °C, unless otherwise specified)

BYP

= 12 V; IO = 100 mA; TJ = -40 °C to 125 °C; V

CC

DRAIN

Symbol Parameter Test conditions Min. Typ. Max. Unit

V

CC

Supply voltage range 4.5 40 V

Output current range 1 500 mA

I

O

Output current R

Regulation (percentage with
respect to V

V

FB

Feedback Voltage IO = 0 to 0.5A 90 100 110 mV

CC

= 12 V)

= 0.2 Ω 500 mA

FB

V

= 4.5 to 40V,

CC

IO = 100mA; V

DRAIN

= 1V

-1 +1 %

On Mode 450 750

V

LEAK

TR/T

DISC

I

CC

DROP

DRAIN

T

D

Quiescent current (Measured on
VCC pin)

Dropout voltage (V

DRAIN

to GND)

Drain leakage current Shutdown; V

Rise/Fall time of the current on

F

PWM transition

Delay on PWM signal (see

Figure 3)

Low level voltage I

Leakage current V

Load disconnection threshold

DRAIN

-GND)

(V

Shutdown Mode;

= 5 to 12V

V

CC

Shutdown Mode;
V

= 12 to 40V

CC

I

= 100mA 0.12 0.16

O

= 0.5A 0.58 0.9

I

O

= 40V 10 µA

DRAIN

C
T

V
C

V
C

= 10 nF,

SLOPE

= -40 °C to 105 °C

J

rising, V

PWM

= floating,

SLOPE

falling, V

PWM

= floating

SLOPE

= 5mA 0.2 0.5 V

SINK

= 5V 1 µA

DISC

CC

CC

= 12V

= 12V

800 µs

3

1.2

DISC Turn-ON 75

DISC Turn-OFF 110

1

3

= 1 V;

µA

V

µs

mV

Thermal

Protection

Shutdown temperature 155

°C

Hysteresis 25

Logic inputs (PWM and EN)

V

V

Input low level 0.4 V

L

Input high level 1.2 V

H

EN, PWM leakage current V

PWM input leakage current V

= 5V; V

EN

= 40V 60

EN

= 40V 120

PWM

= 5V 2

PWM

µAEN input leakage current V

Note: All devices 100 % production tested at TA = 25 °C. Limits over the operating temperature

range are guaranteed by design.

6/18