ST STCS2A User Manual

Features

■ Up to 40 V input voltage

■ Less than 0.5 V voltage overhead

■ Up to 2 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 STCS2A 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

STCS2A

2 A max constant current LED driver

10

1

PowerSO-10

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 2 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

STCS2ASPR PowerSO-10 600 parts per reel

July 2008 Rev 3 1/18

www.st.com

18

Contents STCS2A

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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STCS2A Application diagram

1 Application diagram

Figure 1. Typical application diagram for 2 A LED current

V

IN

4.5V up to 40V

BAT46ZFILM

R

100 ohm

R

100 ohm

IN

C

0.1µF

ON

OFF

ON

OFF

Load disconnection

Load disconnection (Open Drain output)

(Open Drain output)

BYP

V

CC

PWM

EN

DISC

C

SLOPE

10nF

STCS2A

SLOPE

GND

FB

DRAIN

SOURCE

R

FB

0.05 ohm

C

DRAIN

0.47µF

3/18

Pin configuration STCS2A

2 Pin configuration

Figure 2. Pin connections (top view)

Table 2. Pin description

Pin n° Symbol Note

1V

2 PWM PWM dimming input

3ENShutdown

4 NC No connect

5 DRAIN Internal N-MOSFET drain

6 SOURCE

7FB

8 GND Ground

9 SLOPE Capacitor for slope control

10 DISC Load disconnection flag (open drain)

CC

exp-pad Internally connected to ground

Supply voltage

Internal N-MOSFET source. Reference voltage is 100 mV. An external resistor between SOURCE and GND pins sets different current levels for different application needs

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

STCS2A 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

SOURCE Source pin -0.3 to + 3.3 V

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

+ 3.3 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 according the following formula: T

= TA + (PD x R

J

Junction temperature -40 to 150 °C

Storage temperature range -55 to 150 °C

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

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 PowerSO-10 Unit

R

thJC

R

thJA

R

thJA

R

thJA

1. FR4 with using the recommended pad-layout

2. FR4 with heat sink on board (6 cm

3. FR4 with copper-filled through holes and external heat sink applied.

Thermal resistance junction-case 2 °C/W

Thermal resistance junction-ambient

2

).

(1)

(2)

(3)

50 °C/W

35 °C/W

12 °C/W

5/18

Electrical characteristics STCS2A

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 2000 mA

I

O

Output current R

Regulation (percentage with respect to V

V

FB

Feedback voltage IO = 0 to 2A 90 100 110 mV

CC

= 12 V)

= 50 mΩ 2A

FB

V

= 4.5 to 40 V,

CC

IO = 100 mA; 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 (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

= 2 A 0.58 0.9

I

O

= 40 V 10 µA

DRAIN

C T

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

= 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

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.

6/18