STCS05DR [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： | STCS05DR |
| 厂家： | 
ST |
| 描述： | 0.5 A max constant current LED driver |
| 文件： | 总16页 (文件大小：683K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
STCS05
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
Applications
■ LED constant current supplying for varying
The current is set with external resistor up to 0.5
A with a 10 % precision; a dedicated pin allows
implementing PWM dimming.
input voltages
■ Low voltage lighting
■ Small appliances LED lighting
■ Car LED lights
An open-drain pin output provides information on
load disconnection condition.
Description
The STCS05 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.
Table 1.
Device summary
Order code
Package
Packaging
STCS05DR
SO-8
2500 parts per reel
July 2008
Rev 4
1/16
www.st.com
16
STCS05
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1
7.2
7.3
7.4
Current setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
PWM dimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1
8.2
Reverse polarity protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10
2/16
STCS05
Application diagram
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
PWM
EN
DRAIN
ON
ON
STCS05
CDRAIN
0.47µF
OFF
OFF
DISC
FB
GND
RFB
0.2 ohm
Load disconnection
(Open Drain output)
3/16
Pin configuration
STCS05
1
Pin configuration
Figure 2.
Pin connections (top view)
Table 2.
Pin n°
Pin description
Symbol
Note
1
2
3
4
5
6
7
8
VCC
PWM
EN
Supply voltage
PWM dimming input
Shutdown pin
DRAIN
FB
Internal N-MOSFET drain
External resistor connection for current set (N-MOSFET source)
Ground
GND
N.C.
DISC
In order to guarantee the device works properly it is mandatory to leave this pin floating
Load disconnection flag (open drain)
4/16
STCS05
2
Maximum ratings
Maximum ratings
Table 3.
Absolute maximum ratings
Symbol
VCC
VD
Parameter
Value
Unit
DC supply voltage
Drain voltage
-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
FB
Configuration pins
ESD
Human body model (all pins)
Junction temperature
kV
°C
°C
(1)
TJ
-40 to 150
-55 to 150
TSTG
Storage temperature range
1. TJ is calculated from the ambient temperature TA and the power dissipation PD according the following formula:
TJ = TA + (PD x RthJA). See Figure 12 for details of max power dissipation for ambient temperatures 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.
5/16
Electrical characteristics
STCS05
3
Electrical characteristics
Table 5.
Electrical characteristics
(V = 12 V; I = 100 mA; T = -40 °C to 125 °C; V
= 1 V; C
= 1 µF;
DRAIN
CC
O
J
DRAIN
C
= 100 nF typical values are at T = 25 °C, unless otherwise specified)
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 = 0.2Ω
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
Shutdown; VDRAIN = 40V
VPWM rising, VCC = 12V
VPWM falling, VCC = 12V
ISINK = 5mA
µA
µs
3
Delay on PWM signal (see
Figure 3)
TD
1.2
0.2
Low level voltage
0.5
1
V
Leakage current
DISC
VDISC = 5V
µA
DISC Turn-ON
75
110
155
25
Load disconnection threshold
(VDRAIN-GND)
mV
°C
DISC Turn-OFF
Shutdown temperature
Thermal
Protection
Hysteresis
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
VEN = 40V
2
60
µA
V
PWM = 40V
120
Note:
All devices 100 % production tested at T = 25 °C. Limits over the operating temperature
A
range are guaranteed by design.
6/16
STCS05
4
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
EN
Enable
&
DRAIN
PWM
Logic
PWM
Input
PWM
+
-
100 mV
Logic
Driver
Comp
GND
FB
7/16
Typical performance characteristics
STCS05
5
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
8/16
STCS05
Detail description
6
Detail description
The STCS05 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.
6.1
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
6.2
6.3
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 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 a short delay time T (see Figure 3)
D
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.
6.4
Diagnostic
When STCS05 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.
9/16
Application information
STCS05
7
Application information
7.1
Reverse polarity protection
STCS05 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 to
CC
CC
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 11. Reverse polarity condition
VIN
BAT46
or similar
VCC
DRAIN
FB
PWM
EN
GND
DISC
+
7.2
Thermal considerations
The STCS05 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
10/16
STCS05
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
The following pictures show the maximum power dissipation according to the ambient
temperature:
Figure 12. 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]
11/16
Package mechanical data
STCS05
8
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.
12/16
STCS05
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
13/16
Package mechanical data
STCS05
Tape & reel SO-8 mechanical data
mm.
inch.
Typ.
Dim.
Min.
Typ.
Max.
330
Min.
Max.
A
12.992
0.519
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
14/16
STCS05
9
Revision history
Revision history
Table 6.
Document revision history
Revision
Date
Changes
03-Oct-2007
15-Feb-2008
05-May-2008
02-Jul-2008
1
2
3
4
Initial release.
Modified: Figure 1 on page 3, Figure 4 on page 7, Figure 12 on page 11.
Modified: Table 2 on page 4, pin 7 description.
Modified: Table 5 on page 6.
15/16
STCS05
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