STCS05A
SO-8
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
Applications
•
LED constant current supplying for varying input voltages
•
Low voltage lighting
•
Small appliances LED lighting
0.5 A max constant current LED driver
Datasheet
-
production data
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 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.
Order code
STCS05ADR
Table 1. Device summary
Package
SO-8
Packing
2500 parts per reel
January 2022
This is information on a product in full production.
DocID14510 Rev 3 1/18 www.st.com
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Contents
Contents
8
9
10
STCS05A
Application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Detail description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1
Current setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.2
Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.3
PWM dimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.4
Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1
Reverse polarity protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.2
Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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STCS05A
1 Application diagram
Figure 1. Typical application diagram for 0.5 A LED current
Application diagram
DocID14510 Rev 3 3/18
18
Pin configuration
2 Pin configuration
Figure 2. Pin connections (top view)
STCS05A
5
6
7
8
Pin n°
1
2
3
4
Symbol
V
CC
PWM
EN
DRAIN
FB
GND
SLOPE
DISC
Table 2. Pin description
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). The cathode of the LED and a resistor to ground to set the LED current should be connected at this point.
Ground
Capacitor for slope control
Load disconnection flag (open drain)
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STCS05A
3 Maximum ratings
Maximum ratings
Symbol
Table 3. Absolute maximum ratings
Parameter Value
V
CC
DRAIN
DC supply voltage
Drain pin
PWM, EN, DISC Logic pins
-0.3 to +45
-0.3 to +45
-0.3 to + V
CC
+ 0.3
-0.3 to + 3.3
SLOPE, FB Configuration pins
ESD Human body model (all pins)
Power Dissipation SO-8 T
A
= 25°C
(1)
T
J
T
STG
Junction temperature
Storage temperature range
1. See
Figure 16
for details of max power dissipation for ambient temperature higher than 25 °C
± 2
0.85
-40 to 150
-55 to 150
Note: Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these conditions is not implied.
Symbol
Table 4. Thermal data
Parameter
R thJC
R thJA
Thermal resistance junction-case
Thermal resistance junction-ambient
(1)
1. This value depends from thermal design of PCB on which the device is mounted.
SO-8
20
100
Unit
°C/W
°C/W
Unit
V
W
°C
°C
V
V kV
DocID14510 Rev 3 5/18
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Electrical characteristics
4 Electrical characteristics
STCS05A
Table 5. Electrical characteristics (V
CC
= 12 V; I
O
= 100 mA; T
J
= -40 °C to 125 °C; V
DRAIN
= 1 V;
C
DRAIN
= 1 µF; C
BYP
= 100 nF typical values are at T
A
= 25 °C, unless otherwise specified)
Symbol Parameter Test conditions Min.
Typ.
Max.
Unit
V
V
I
CC
O
FB
Supply voltage range
Output current range
Output current
Regulation (percentage with respect to V
CC
= 12 V)
Feedback Voltage
R
FB
= 0.2 Ω
V
CC
= 4.5 to 40 V,
I
O
= 100 mA; V
DRAIN
= 1 V
I
O
= 0 to 0.5 A
On Mode
V
T
I
CC
DROP
LEAK
DRAIN
R
T
/T
D
F
DISC
Quiescent current (Measured on
V
CC
pin)
Dropout voltage (V
DRAIN to GND)
Drain leakage current
Rise/Fall time of the current on
PWM transition
Delay on PWM signal (see
Figure 3 )
Low level voltage
Leakage current
Load disconnection threshold
(V
DRAIN
-GND)
Shutdown Mode;
V
CC
= 5 to 12 V
Shutdown Mode;
V
CC
= 12 to 40 V
I
O
= 100 mA
I
O
= 0.5 A
Shutdown; V
DRAIN
= 40 V
C
SLOPE
= 10 nF,
T
J
= -40 °C to 105 °C
V
PWM
rising, V
CC
= 12 V
C
SLOPE
= floating
V
PWM
falling, V
CC
= 12 V
C
SLOPE
= floating
I
SINK
= 5 mA
V
DISC
= 5 V
DISC Turn-ON
DISC Turn-OFF
Shutdown temperature
Thermal
Protection
Hysteresis
Logic inputs (PWM and EN)
4.5
1
-1
90
500
100
450
0.12
0.58
800
3
1.2
0.2
75
110
155
25
40
500
+1
110
750
1
3
0.16
0.9
10
0.5
1
V mA mA
% mV
µA
V
µA
µs
µs
V
µA mV
°C
V
L
V
H
Input low level
Input high level
EN, PWM leakage current
EN input leakage current
PWM input leakage current
V
EN
= 5 V; V
PWM
= 5 V
V
EN
= 40 V
V
PWM
= 40 V
1.2
0.4
2
60
120
V
V
µA
Note:
6/18
All devices 100 % production tested at T
A
= 25 °C. Limits over the operating temperature range are guaranteed by design.
DocID14510 Rev 3
STCS05A
5 Timing
Figure 3. PWM and output current timing
Timing
Figure 4. Block diagram
Shutdown all blocks
Thermal
Shutdown
-
+
-
+
DocID14510 Rev 3 7/18
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Typical performance characteristics
6 Typical performance characteristics
Figure 5. I
DRAIN
vs. V
CC
, T
A
= 25 °C Figure 6. I
DRAIN
vs. R
SET
STCS05A
Figure 7. I
DRAIN
vs. V
CC
, T
A
= 25 °C
[ Ω ]
Figure 8. V
DROP
(including V
FB
) vs. temperature
Figure 9. I
CC
vs. temperature Figure 10. I
CC
vs. V
CC
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STCS05A
Figure 11. T rise
/T fall
vs. C
SLOPE
Typical performance characteristics
Figure 12. Turn-on time
I
DRAIN
= 80 mA - C
SLOPE
= 10nF - T
A
= 25° C
Figure 13. Rise time
I
DRAIN
= 80 mA - C
SLOPE
= 10nF - T
A
= 25° C
V
PWM
2V/DIV
I
DRAIN
20mA/DIV
V
DRAIN
1V/DIV
Time 210µsec/DIV
Figure 14. Fall time
I
DRAIN
= 80 mA - C
SLOPE
= 10nF - T
A
= 25° C
V
PWM
2V/DIV
I
DRAIN
20mA/DIV
V
DRAIN
1V/DIV
Time 200µsec/DIV
V
PWM
2V/DIV
I
DRAIN
20mA/DIV
V
DRAIN
1V/DIV
Time 200µsec/DIV
DocID14510 Rev 3 9/18
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Detail description
7 Detail description
STCS05A
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 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
7.2
7.3
Current setting
The current is set with an external sensing resistor connected to the FB pin. The feedback voltage is 100 mV, then a low resistor value can be chosen reducing power dissipation. A value between 1 mA and 500 mA can be set according to the resistor value, the resulting output current has a tolerance of ± 10 %.
For instance, should one need a 350 mA LEDs current, R
F
should be selected according to the following equation:
R
F
= V
FB
/ I
LEDs
= 100 mV / 350 mA = 284 m
Ω
Enable
When the enable pin is low the device completely off thus reducing current consumption to less than 1 µA. When in shutdown mode, the internal main switch is off.
PWM dimming
The PWM input allows implementing PWM dimming on the LED current; when the PWM input is high the main switch will be on and vice versa. A typical frequency range for the input is from few Hertz to 50 kHz. The maximum dimming frequency is limited by the minimum rise/fall time of the current (obtained with C
SLOPE
= 0) which is around 4 µs each.
Above 50 kHz the current waveforms starts assuming a triangular shape.
While the PWM input is switching, the overall circuitry remains on, this is needed in order to implement two important features: short delay time and controlled slope for the current.
Since the PWM pin is controlling just the main switch, the overall circuitry is always on and it is able to control the delay time between the PWM input signal and the output current in the range of few µs, this is important to implement synchronization among several light LED sources.
The rise and fall slope of the current is controlled by the C
SLOPE
capacitor. The rise and fall time are linear dependent from the C
SLOPE
capacitor value (see graph in typical characteristics). A controlled rise time has two main benefits: reducing EMI noise and avoid current spike at turn on.
When C
SLOPE
is left floating, the internal switch is turned on at maximum speed, in this condition an overshoot can be present on the LED current before the system goes into regulation.
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STCS05A
7.4
Detail description
Diagnostic
When STCS05A is in on mode (EN is high), the device is able to detect disconnection or fail of the LED string monitoring V
DRAIN
pin. If V
DRAIN
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.
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Application information
8 Application information
8.1
STCS05A
Reverse polarity protection
STCS05A must be protected from reverse connection of the supply voltage. Since the current sunk from V
CC
pin is in the range of 450 µA a small diode connected to V
CC
is able to protect the chip. Care must be taken for the whole application circuit, especially for the
LEDs, in fact, in case a negative voltage is applied between V
IN
and GND, a negative voltage will be applied to the LED string that must have a total breakdown voltage higher than the negative applied voltage in order to avoid any damage.
Figure 15. Reverse polarity condition
8.2 Thermal considerations
The STCS05A is able to control a LED current up to 500 mA and able to sustain a voltage on the drain pin up to 40 V. Those operating conditions are however limited by thermal constraints, the thermal resistances shown in the thermal data section is the typical ones.
The power dissipation in the device can be calculated as follow:
P
D
= (V
DRAIN
- V
FB
) x I
LED
+ (V
CC x I
CC
) basing on this and on the thermal resistance and ambient temperature, the junction temperature can be calculated as:
T
J
= R thJA
x P
D
+ T
A
A typical application could be:
– Input voltage: 12 V;
– 3 white LEDs with an typical V
F
= 3.6 V;
– LEDs current: 350 mA;
– Package: SO-8;
12/18 DocID14510 Rev 3
STCS05A Application information
– T
A
= 50 °C;
In this case V
DRAIN
= 12 - 3 x 3.6 = 1.2 V
P
D
= (1.2 - 0.1) x 0.35 + 12 x 0.5 x 10
-3
= 0.385 + 6 x 10
-3
= 391 mW
The junction temperature will be:
T
J
= 100 x 0.391 + 50 = 89 °C
For a correct operation of the chip, the junction temperature must not exceed 110 °C.
The following pictures show the maximum power dissipation according to the ambient temperature:
Figure 16. Maximum power dissipation vs T
A
for SO-8
25 35 45 55 65 75 85 95 105 115 125
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Package mechanical data
9 Package mechanical data
STCS05A
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK
®
packages, depending on their level of environmental compliance. ECOPACK
® specifications, grade definitions and product status are available at: www.st.com
.
ECOPACK
®
is an ST trademark.
14/18 DocID14510 Rev 3
Dim.
h
L k ddd e
H
D
E
A
A1
A2
B
C
STCS05A
Min.
1.35
0.10
1.10
0.33
0.19
4.80
3.80
5.80
0.25
0.40
SO-8 mechanical data
mm.
Typ.
Max.
1.75
0.25
1.65
0.51
0.25
5.00
4.00
Min.
0.053
0.04
0.043
0.013
0.007
0.189
0.150
1.27
6.20
0.50
1.27
8° (max.)
0.228
0.010
0.016
0.1
Package mechanical data inch.
Typ.
0.050
0.244
0.020
0.050
0.04
Max.
0.069
0.010
0.065
0.020
0.010
0.197
0.157
DocID14510 Rev 3
0016023/C
15/18
18
Package mechanical data
Tape & reel SO-8 mechanical data
Min.
mm.
Typ.
Min.
Dim.
A
C
D
N
T
Ao
Bo
Ko
Po
P
12.8
20.2
60
8.1
5.5
2.1
3.9
7.9
Max.
330
13.2
22.4
8.5
5.9
2.3
4.1
8.1
0.504
0.795
2.362
0.319
0.216
0.082
0.153
0.311
inch.
Typ.
STCS05A
Max.
12.992
0.519
0.882
0.335
0.232
0.090
0.161
0.319
16/18 DocID14510 Rev 3
STCS05A
10 Revision history
Date
04-Mar-2008
02-Jul-2008
20-Jan-2022
Revision
1
2
3
Table 6. Document revision history
Changes
Initial release.
Modified: Table 5 on page 6.
Updated: Applications on the cover page.
Revision history
DocID14510 Rev 3 17/18
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STCS05A
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18/18 DocID14510 Rev 3
