ST STCS1A User Manual

Features

■ Up to 40 V input voltage

■ Less than 0.5 V voltage overhead

■ Up to 1.5 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

STCS1A

1.5 A max constant current LED driver

DFN8 (3 x 3 mm)

The current is set with external resistor up to 1.5
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.

Power SO-8

The STCS1A 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
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.

Table 1. Device summary

Order codes Packages Packaging

STCS1APUR DFN8 (3 x 3 mm) 3000 parts per reel

STCS1APHR Power SO-8 2500 parts per reel

July 2008 Rev 2 1/19

www.st.com

19

Contents STCS1A

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2/19

STCS1A 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

STCS1A

STCS1A

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

3/19

Pin configuration STCS1A

2 Pin configuration

Figure 2. Pin connections (top view)

DFN8

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

Exp-pad Internally connected to ground.

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.

PowerSO-8

4/19

STCS1A 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)

T

J

T

STG

1. TJ is calculated from the ambient temperature TA and the power dissipation PD accoring the following formula:
= TA + (PD x R

T

J

than 25°C.

Junction temperature -40 to 150 °C

Storage temperature range -55 to 150 °C

). See Figure 16 and Figure 17 for details of max power dissipation for ambient temperatures higher

thJA

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 DFN8 Power SO-8 Unit

R

thJC

R

thJA

1. This value is referred to four-layer PCB, JEDEC standard test board.

2. With two sides, two planes PCB following EIA/JEDEC JESD51-7 standard.

Thermal resistance junction-case 10 12 °C/W

Thermal resistance junction-ambient 37.6

(1)

45

(2)

°C/W

5/19

Electrical characteristics STCS1A

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 1500 mA

I

O

Output current R

Regulation (percentage with
respect to V

V

FB

Feedback voltage IO = 0 to 1.5A 90 100 110 mV

CC

=12V)

= 0.2 Ω 500 mA

FB

V

= 4.5 to 40 V,

CC

IO = 100mA; V

DRAIN

= 1 V

-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 1)

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

= 100 mA 0.12 0.16

O

= 1.5 A 0.58 0.9

I

O

= 40 V 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

= 5 mA 0.2 0.5 V

SINK

= 5 V 1 µA

DISC

CC

CC

= 12 V

= 12 V

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

= 5 V; V

EN

= 40 V 60

EN

= 40 V 120

PWM

= 5 V 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.

6/19