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July 2008 Rev 2 1/19

STCS1A

1.5 A max constant current LED driver

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

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.

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

DFN8 (3 x 3 mm)

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

www.st.com

Summary of content (19 pages)

PAGE 1
STCS1A 1.5 A max constant current LED driver 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 DFN8 (3 x 3 mm) Power SO-8 Applications ■ LED constant current supplying for varying input voltages ■ Low voltage lighting ■ Small appliances LED lighting ■ Car LED lights The current is set with external resistor up to 1.
PAGE 2
Contents STCS1A Contents 1 Application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Timing . . . . . . . . . . . . . . . . . . . .
PAGE 3
STCS1A 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 ON PWM ON EN OFF OFF DISC Load disconnection (Open Drain output) DRAIN STCS1A CDRAIN 0.47µF SLOPE GND FB CSLOPE 10nF RFB 0.
PAGE 4
Pin configuration STCS1A 2 Pin configuration Figure 2. Pin connections (top view) PowerSO-8 DFN8 Table 2. Pin description Pin n° Symbol 1 VCC 2 PWM 3 EN 4 DRAIN 5 FB 6 GND 7 SLOPE 8 DISC Exp-pad 4/19 Note Supply voltage PWM dimming input Shutdown pin Internal N-MOSFET drain Feedback input. The control loop regulates the current in such a way that the average voltage at the FB input is 100 mV (nominal).
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STCS1A Maximum ratings 3 Maximum ratings Table 3. Absolute maximum ratings Symbol VCC Parameter Value Unit DC supply voltage -0.3 to +45 DRAIN Drain pin -0.3 to +45 PWM, EN, DISC Logic pins -0.3 to + VCC + 0.3 V -0.3 to + 3.3 V ±2 kV Junction temperature -40 to 150 °C Storage temperature range -55 to 150 °C V SLOPE, FB ESD TJ (1) TSTG Configuration pins Human body model (all pins) 1.
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Electrical characteristics STCS1A 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 VCC IO VFB Parameter Test conditions Min. VDROP TD 40 V Output current range 1 1500 mA Output current RFB = 0.2 Ω Regulation (percentage with respect to VCC=12V) VCC = 4.
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STCS1A Timing 5 Timing Figure 3. PWM and output current timing PWM 90% Current 10% TD Figure 4. Trise TD Block diagram High Voltage 45 V VCC Tfall Preregulator 3.3 V Low Voltage 3.3 V H.V. 45 V Thermal Shutdown Bandgap 1.
PAGE 8
Typical performance characteristics STCS1A 6 Typical performance characteristics Figure 5. IDRAIN vs VCC, TA = 25°C Figure 6. IDRAIN vs RSET Figure 7. IDRAIN vs Temperature Figure 8. VDROP (including VFB) vs temperature Figure 9. ICC vs Temperature Figure 10.
PAGE 9
STCS1A Figure 11. Trise/Tfall vs CSLOPE Typical performance characteristics Figure 12. Turn-on time CSLOPE = floating Figure 13. Dimming operation: Rise Figure 14.
PAGE 10
Detail description 7 STCS1A Detail description 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. 7.1 Current setting The current is set with an external sensing resistor connected to the FB pin.
PAGE 11
STCS1A 7.4 Detail description Diagnostic When STCS1A is in on mode (EN is high), the device is able to detect disconnection or fail of the LED string monitoring VDRAIN pin. If VDRAIN is lower than 75 mV the DISC pin is pulled low regardless the PWM pin status. This information can be used by the system to inform that some problem happens in the LEDs.
PAGE 12
Application information STCS1A 8 Application information 8.1 Reverse polarity protection STCS1A must be protected from reverse connection of the supply voltage. Since the current sunk from VCC pin is in the range of 450 µA a small diode connected to VCC is able to protect the chip.
PAGE 13
STCS1A Application information – LEDs current: 500 mA; – Package: DFN8 3x3 mm; – TA = 50°C; In this case VDRAIN = 12 - 3 x 3.6 = 1.2 V PD = (1.2 - 0.1) x 0.5 + 12 x 0.5 x 10-3 = 0.55 + 6 x 10-3 = 556 mW The junction temperature will be: TJ = 37.6 x 0.556 + 50 = 70.9 °C The following pictures show the maximum power dissipation according to the ambient temperature for both packages: Figure 16. Maximum power dissipation vs TA for DFN8 3x3 mm Figure 17. Maximum power dissipation vs TA for PowerSO-8 3.00 3.
PAGE 14
Package mechanical data 9 STCS1A Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a lead-free second level interconnect. The category of second Level Interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.
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STCS1A Package mechanical data DFN8 (3x3 mm) mechanical data mm. mils. Dim. Min. Typ. Max. Min. Typ. Max. 0.80 0.90 1.00 31.5 35.4 39.4 A1 0.02 0.05 0.8 2.0 A2 0.70 27.6 A3 0.20 7.9 A b 0.18 D D2 2.23 7.1 2.38 1.49 1.64 2.48 87.8 0.40 11.8 93.7 97.7 118.1 1.74 58.7 0.50 0.30 9.1 118.1 3.00 e L 0.30 3.00 E E2 0.23 64.6 68.5 19.7 0.50 11.8 15.7 19.
PAGE 16
Package mechanical data STCS1A PowerSO-8 mechanical data Dim. mm. Min. Typ. A inch. Max. Min. Typ. 1.70 A1 0.00 A2 1.25 b 0.31 c 0.17 D 4.80 D1 0.067 0.00 0.006 0.049 0.142 0.51 0.012 0.020 0.25 0.007 0.010 4.90 5.00 0.189 0193 0.197 2.24 3.10 3.20 0.088 0.122 0.126 E 5.80 6.00 6.20 0.228 0.236 0.244 E1 3.80 3.90 4.00 0.150 0.154 0.157 E2 1.55 2.41 2.51 0.061 0.095 0.099 e 0.15 Max. 1.27 0.050 h 0.25 0.50 0.010 0.020 L 0.40 1.27 0.
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STCS1A Package mechanical data Tape & reel QFNxx/DFNxx (3x3) mechanical data mm. inch. Dim. Min. Typ. A Max. Min. Typ. 180 13.2 7.087 C 12.8 D 20.2 0.795 N 60 2.362 T Max. 0.504 0.519 14.4 0.567 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.
PAGE 18
Revision history STCS1A 10 Revision history Table 6. Document revision history Date Revision 19-Feb-2008 1 Initial release. 02-Jul-2008 2 Modified: Table 5 on page 6.
PAGE 19
STCS1A Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.