STCS05ADR [STMICROELECTRONICS]
0.5 A max constant current LED driver; 0.5 A的最大恒定电流LED驱动器
| 型号： | STCS05ADR |
| 厂家： | 
ST |
| 描述： | 0.5 A max constant current LED driver |
| 文件： | 总18页 (文件大小：854K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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
SO-8
■ LED disconnection diagnostic
■ Slope control with external cap
Applications
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.
■ 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 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.
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
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
18
Contents
STCS05A
Contents
1
2
3
4
5
6
7
Application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Detail description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1
7.2
7.3
7.4
Current setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
PWM dimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1
8.2
Reverse polarity protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10
2/18
STCS05A
1
Application diagram
Application diagram
Figure 1.
Typical application diagram for 0.5 A LED current
VIN
4.5V to 40V
BAT46ZFILM
CBYP
RIN 100 ohm
0.1µF
VCC
PWM
EN
DRAIN
ON
ON
STCS05A
CDRAIN
0.47µF
OFF
OFF
DISC
FB
SLOPE GND
RFB
0.2 ohm
CSLOPE
10nF
Load disconnection
(Open Drain output)
3/18
Pin configuration
STCS05A
2
Pin configuration
Figure 2.
Pin connections (top view)
Table 2.
Pin n°
Pin description
Symbol
Note
1
2
3
4
VCC
PWM
EN
Supply voltage
PWM dimming input
Shutdown pin
DRAIN
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.
5
FB
6
7
8
GND
SLOPE
DISC
Ground
Capacitor for slope control
Load disconnection flag (open drain)
4/18
STCS05A
3
Maximum ratings
Maximum ratings
Table 3.
Absolute maximum ratings
Symbol
VCC
DRAIN
Parameter
Value
Unit
DC supply voltage
Drain pin
-0.3 to +45
-0.3 to +45
-0.3 to + VCC + 0.3
-0.3 to + 3.3
2
V
PWM, EN, DISC Logic pins
V
V
SLOPE, FB
ESD
Configuration pins
Human body model (all pins)
kV
W
°C
°C
Power Dissipation SO-8 TA=25°C (1)
0.85
TJ
Junction temperature
-40 to 150
-55 to 150
TSTG
Storage temperature range
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
Thermal resistance junction-case
Thermal resistance junction-ambient (1)
SO-8
Unit
RthJC
RthJA
20
°C/W
°C/W
100
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 (V = 12 V; I = 100 mA; T = -40 °C to 125 °C; V
= 1 V;
DRAIN
CC
O
J
C
= 1 µF; C
= 100 nF typical values are at T = 25 °C, unless otherwise specified)
DRAIN
BYP A
Symbol
Parameter
Test conditions
Min.
Typ.
Max.
Unit
VCC
Supply voltage range
Output current range
Output current
4.5
1
40
V
500
mA
mA
IO
RFB = 0.2 Ω
500
Regulation (percentage with
respect to VCC = 12 V)
VCC = 4.5 to 40V,
IO = 100mA; VDRAIN = 1V
-1
+1
%
VFB
Feedback Voltage
IO = 0 to 0.5A
On Mode
90
100
450
110
750
mV
Shutdown Mode;
VCC = 5 to 12V
Quiescent current (Measured on
VCC pin)
1
3
ICC
µA
Shutdown Mode;
VCC = 12 to 40V
IO = 100mA
0.12
0.58
0.16
0.9
10
VDROP
Dropout voltage (VDRAIN to GND)
V
IO = 0.5A
LEAKDRAIN Drain leakage current
Rise/Fall time of the current on
Shutdown; VDRAIN = 40V
µA
µs
CSLOPE = 10 nF,
TJ = -40 °C to 105 °C
TR/TF
800
3
PWM transition
VPWM rising, VCC = 12V
CSLOPE = floating,
Delay on PWM signal (see
Figure 3)
TD
µs
VPWM falling, VCC = 12V
1.2
0.2
CSLOPE = floating
Low level voltage
Leakage current
ISINK = 5mA
0.5
1
V
V
DISC = 5V
µA
DISC
DISC Turn-ON
DISC Turn-OFF
75
110
155
25
Load disconnection threshold
(VDRAIN-GND)
mV
°C
Shutdown temperature
Hysteresis
Thermal
Protection
Logic inputs (PWM and EN)
VL
Input low level
0.4
V
V
VH
Input high level
1.2
EN, PWM leakage current
EN input leakage current
PWM input leakage current
VEN = 5V; VPWM = 5V
2
V
EN = 40V
60
µA
VPWM = 40V
120
Note:
All devices 100 % production tested at T = 25 °C. Limits over the operating temperature
A
range are guaranteed by design.
6/18
STCS05A
5
Timing
Timing
Figure 3.
PWM and output current timing
PWM
90%
10%
Current
TD
Trise
TD Tfall
Figure 4.
Block diagram
H.V.
45 V
High Voltage
45 V
Low Voltage 3.3 V
Thermal
Shutdown
Bandgap
1.23 V
Preregulator
3.3 V
VCC
DISC
Shutdown
all blocks
+
75 mV
-
Disc
comp
Enable
Input
Enable,
PWM &
EN
DRAIN
Slope controll
Logic
PWM
Input
PWM
+
Logic
-
100 mV
Driver
Comp
Slope
Control
GND
FB
SLOPE
7/18
Typical performance characteristics
STCS05A
6
Typical performance characteristics
Figure 5.
I
vs V , T = 25 °C
Figure 6.
I
vs R
SET
DRAIN
CC
A
DRAIN
1000
100
10
1
0.1
1
10
100
RFB [Ω]
Figure 7.
I
vs temperature
Figure 8.
V
(including V ) vs
DRAIN
DROP FB
temperature
Figure 9.
I
vs temperature
Figure 10. I vs V
CC CC
CC
8/18
STCS05A
Typical performance characteristics
Figure 11. T /T vs C
Figure 12. Turn-on time
rise fall
SLOPE
IDRAIN = 80 mA - CSLOPE = 10nF - TA = 25° C
VPWM 2V/DIV
DRAIN 20mA/DIV
I
VDRAIN 1V/DIV
Time 210µsec/DIV
Figure 13. Rise time
Figure 14. Fall time
IDRAIN = 80 mA - CSLOPE = 10nF - TA = 25° C
IDRAIN = 80 mA - CSLOPE = 10nF - TA = 25° C
VPWM 2V/DIV
DRAIN 20mA/DIV
DRAIN 1V/DIV
Time 200µsec/DIV
VPWM 2V/DIV
IDRAIN 20mA/DIV
DRAIN 1V/DIV
Time 200µsec/DIV
I
V
V
9/18
Detail description
STCS05A
7
Detail 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.
7.1
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 should be selected according to
F
the following equation:
R = V / I
= 100 mV / 350 mA = 284 mΩ
F
FB LEDs
7.2
7.3
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
= 0) which is around 4 µs each.
SLOPE
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
capacitor. The rise and fall
SLOPE
time are linear dependent from the C
capacitor value (see graph in typical
SLOPE
characteristics). A controlled rise time has two main benefits: reducing EMI noise and avoid
current spike at turn on.
When C
is left floating, the internal switch is turned on at maximum speed, in this
SLOPE
condition an overshoot can be present on the LED current before the system goes into
regulation.
10/18
STCS05A
Detail description
7.4
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 pin. If V is lower than 75 mV the DISC pin is
DRAIN
DRAIN
pulled low regardless the PWM pin status. This information can be used by the system to
inform that some problem happens in the LEDs.
11/18
Application information
STCS05A
8
Application information
8.1
Reverse polarity protection
STCS05A must be protected from reverse connection of the supply voltage. Since the
current sunk from V pin is in the range of 450 µA a small diode connected to V is able
CC
CC
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 and GND, a negative
IN
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
VIN
BAT46
or similar
DRAIN
VCC
PWM
EN
FB
DISC
SLOPE GND
+
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 = (V
- V ) x I
+ (V x I
)
CC
D
DRAIN
FB
LED
CC
basing on this and on the thermal resistance and ambient temperature, the junction
temperature can be calculated as:
T = R
x P + T
D A
J
thJA
A typical application could be:
– Input voltage: 12 V;
– 3 white LEDs with an typical V = 3.6 V;
F
– LEDs current: 350 mA;
– Package: SO-8;
– T = 50 °C;
A
12/18
STCS05A
Application information
In this case V
= 12 - 3 x 3.6 = 1.2 V
DRAIN
-3
-3
P = (1.2 - 0.1) x 0.35 + 12 x 0.5 x 10 = 0.385 + 6 x 10 = 391 mW
D
The junction temperature will be:
T = 100 x 0.391 + 50 = 89 °C
J
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 for SO-8
A
1.40
1.20
1.00
0.80
0.60
RthJA = 100 [°C/W]
0.40
0.20
PDMAX = (TJMAX-TA)/RthJA
25
35
45
55
65
75
85
95 105 115 125
[°C]
13/18
Package mechanical data
STCS05A
9
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.st.com.
14/18
STCS05A
Package mechanical data
SO-8 mechanical data
mm.
inch.
Dim.
Min.
Typ.
Max.
Min.
Typ.
Max.
A
A1
A2
B
1.35
1.75
0.053
0.069
0.10
1.10
0.33
0.19
4.80
3.80
0.25
1.65
0.51
0.25
5.00
4.00
0.04
0.010
0.065
0.020
0.010
0.197
0.157
0.043
0.013
0.007
0.189
0.150
C
D
E
e
1.27
0.050
H
5.80
0.25
0.40
6.20
0.50
1.27
0.228
0.010
0.016
0.244
0.020
0.050
h
L
k
8° (max.)
ddd
0.1
0.04
0016023/C
15/18
Package mechanical data
STCS05A
Tape & reel SO-8 mechanical data
mm.
inch.
Typ.
Dim.
Min.
Typ.
Max.
330
Min.
Max.
12.992
0.519
A
C
D
12.8
20.2
60
13.2
0.504
0.795
2.362
N
T
22.4
8.5
5.9
2.3
4.1
8.1
0.882
0.335
0.232
0.090
0.161
0.319
Ao
Bo
Ko
Po
P
8.1
5.5
2.1
3.9
7.9
0.319
0.216
0.082
0.153
0.311
16/18
STCS05A
Revision history
10
Revision history
Table 6.
Date
Document revision history
Revision
Changes
04-Mar-2008
02-Jul-2008
1
2
Initial release.
Modified: Table 5 on page 6.
17/18
STCS05A
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