ST STCS05A User Manual

STCS05A

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

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

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

2/18

STCS05A	Application diagram

1 Application diagram

Figure 1. Typical application diagram for 0.5 A LED current

VIN

4.5V to 40V

BAT46ZFILM
RIN 100 ohm CBYP
0.1µF	VCC		DRAIN
ON	PWM	STCS05A		CDRAIN
OFF
				0.47µF
ON	EN
OFF	DISC	SLOPE GND FB
Load disconnection		CSLOPE	RFB
			0.2 ohm
(Open Drain output)		10nF

3/18

Pin configuration	STCS05A

2 Pin configuration

Figure 2. Pin connections (top view)

Table 2.	Pin description
Pin n°	Symbol	Note
1	VCC	Supply voltage
2	PWM	PWM dimming input
3	EN	Shutdown pin
4	DRAIN	Internal N-MOSFET drain
		Feedback input. The control loop regulates the current in such a way that the average
5	FB	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.
6	GND	Ground
7	SLOPE	Capacitor for slope control
8	DISC	Load disconnection flag (open drain)

4/18

STCS05A						Maximum ratings
3	Maximum ratings
Table 3.	Absolute maximum ratings
Symbol			Parameter			Value		Unit
VCC			DC supply voltage			-0.3 to +45		V
DRAIN			Drain pin			-0.3 to +45
PWM, EN, DISC			Logic pins		-0.3 to + VCC + 0.3			V
SLOPE, FB			Configuration pins			-0.3 to + 3.3		V
ESD			Human body model (all pins)		±2			kV
Power Dissipation			SO-8 T =25°C (1)		0.85			W
			A
TJ			Junction temperature			-40 to 150		°C
TSTG			Storage temperature range			-55 to 150		°C
1. See Figure 16 for details of max power dissipation for ambient temperature higher than 25 °C
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
RthJC		Thermal resistance junction-case				20		°C/W
R		Thermal resistance junction-ambient (1)				100		°C/W
thJA

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

5/18

Electrical characteristics							STCS05A
4		Electrical characteristics
Table 5.		Electrical characteristics (VCC = 12 V; IO = 100 mA; TJ = -40 °C to 125 °C; VDRAIN = 1 V;
		CDRAIN = 1 µF; CBYP = 100 nF typical values are at TA = 25 °C, unless otherwise specified)
Symbol		Parameter		Test conditions	Min.	Typ.	Max.	Unit
VCC		Supply voltage range			4.5		40	V
		Output current range			1		500	mA
	IO	Output current		RFB = 0.2 Ω		500		mA
		Regulation (percentage with		VCC = 4.5 to 40V,	-1		+1	%
		respect to VCC = 12 V)		IO = 100mA; VDRAIN = 1V
VFB		Feedback Voltage		IO = 0 to 0.5A	90	100	110	mV
				On Mode		450	750
		Quiescent current (Measured on		Shutdown Mode;			1
	ICC			VCC = 5 to 12V				µA
		VCC pin)
				Shutdown Mode;			3
				VCC = 12 to 40V
V		Dropout voltage (V	to GND)	IO = 100mA		0.12	0.16	V
	DROP
		DRAIN		IO = 0.5A		0.58	0.9
LEAKDRAIN		Drain leakage current		Shutdown; VDRAIN = 40V			10	µA
TR/TF		Rise/Fall time of the current on		CSLOPE = 10 nF,		800		µs
		PWM transition		TJ = -40 °C to 105 °C
				VPWM rising, VCC = 12V		3
	TD	Delay on PWM signal (see		CSLOPE = floating,				µs
		Figure 3)		VPWM falling, VCC = 12V		1.2
				CSLOPE = floating
		Low level voltage		ISINK = 5mA		0.2	0.5	V
DISC		Leakage current		VDISC = 5V			1	µA
		Load disconnection threshold		DISC Turn-ON		75		mV
		(VDRAIN-GND)		DISC Turn-OFF		110
Thermal		Shutdown temperature				155		°C
Protection		Hysteresis				25
Logic inputs (PWM and EN)
	VL	Input low level					0.4	V
	VH	Input high level			1.2			V
		EN, PWM leakage current		VEN = 5V; VPWM = 5V			2
		EN input leakage current		VEN = 40V			60	µA
		PWM input leakage current		VPWM = 40V			120
Note:		All devices 100 % production tested at TA = 25 °C. Limits over the operating temperature
		range are guaranteed by design.
6/18