STCS1APHR [STMICROELECTRONICS]
1.5 A max constant current LED driver; 1.5 A的最大恒定电流LED驱动器型号: | STCS1APHR |
厂家: | ST |
描述: | 1.5 A max constant current LED driver |
文件: | 总19页 (文件大小:449K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
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
DFN8 (3 x 3 mm)
Power SO-8
■ LED disconnection diagnostic
■ Slope control with external cap
Applications
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.
■ LED constant current supplying for varying
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 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.
Table 1.
Device summary
Order codes
Packages
Packaging
STCS1APUR
STCS1APHR
DFN8 (3 x 3 mm)
Power SO-8
3000 parts per reel
2500 parts per reel
July 2008
Rev 2
1/19
www.st.com
19
Contents
STCS1A
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10
2/19
STCS1A
1
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
DRAIN
ON
ON
PWM
STCS1A
CDRAIN
0.47µF
OFF
OFF
EN
DISC
FB
SLOPE GND
RFB
0.2 ohm
CSLOPE
10nF
Load disconnection
(Open Drain output)
3/19
Pin configuration
STCS1A
2
Pin configuration
Figure 2.
Pin connections (top view)
PowerSO-8
DFN8
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)
Internally connected to ground.
Exp-pad
4/19
STCS1A
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)
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 accoring the following formula:
TJ = TA + (PD x RthJA). See Figure 16 and Figure 17 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.
Symbol
Thermal data
Parameter
DFN8
Power SO-8
Unit
RthJC
RthJA
Thermal resistance junction-case
Thermal resistance junction-ambient
10
12
°C/W
°C/W
37.6 (1)
45 (2)
1. This value is referred to four-layer PCB, JEDEC standard test board.
2. With two sides, two planes PCB following EIA/JEDEC JESD51-7 standard.
5/19
Electrical characteristics
STCS1A
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
1500
mA
mA
IO
RFB = 0.2 Ω
500
Regulation (percentage with
respect to VCC=12V)
VCC = 4.5 to 40 V,
IO = 100mA; VDRAIN = 1 V
-1
+1
%
VFB
Feedback voltage
IO = 0 to 1.5A
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 = 100 mA
0.12
0.58
0.16
0.9
10
VDROP
Dropout voltage (VDRAIN to GND)
V
IO = 1.5 A
LEAKDRAIN Drain leakage current
Rise/Fall time of the current on
Shutdown; VDRAIN = 40 V
µA
µs
CSLOPE = 10 nF,
TJ = -40 °C to 105 °C
TR/TF
800
3
PWM transition
VPWM rising, VCC = 12 V
CSLOPE = floating
Delay on PWM signal
(see Figure 1)
TD
µs
VPWM falling, VCC = 12 V
1.2
0.2
CSLOPE = floating
Low level voltage
Leakage current
ISINK = 5 mA
0.5
1
V
V
DISC = 5 V
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 = 5 V; VPWM = 5 V
2
V
EN = 40 V
60
µA
VPWM = 40 V
120
Note:
All devices 100 % production tested at T = 25 °C. Limits over the operating temperature
A
range are guaranteed by design.
6/19
STCS1A
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
7/19
Typical performance characteristics
STCS1A
6
Typical performance characteristics
Figure 5.
I
vs V , T = 25°C
Figure 6.
I
vs R
DRAIN SET
DRAIN
CC
A
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
8/19
STCS1A
Typical performance characteristics
Figure 11. T /T vs C
Figure 12. Turn-on time
rise fall
SLOPE
CSLOPE = floating
Figure 13. Dimming operation: Rise
Figure 14. Dimming operation: Fall
CSLOPE = 1nF
CSLOPE = 1nF
9/19
Detail description
STCS1A
7
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. The feedback
voltage is 100 mV, then a low resistor value can be chosen reducing power dissipation. A
value between 1 for instance, should one need a 700 mA LEDs current, R should be
F
selected according to the following equation:
For instance, should one need a 700 mA LEDs current, R should be selected according to
F
the following equation:
R = V / I
= 100 mV / 700 mA = 142 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 4µs 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.
10/19
STCS1A
Detail description
7.4
Diagnostic
When STCS1A 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.
11/19
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 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 15. Reverse polarity condition
VIN
BAT46
or similar
DRAIN
VCC
PWM
EN
FB
DISC
SLOPE GND
+
8.2
Thermal considerations
The STCS1A is able to control a LED current up to 1.5 A 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 are the typical ones,
in particular R
depends on the copper area and the number of layers of the printed
thJA
circuit board under the pad. DFN8 and PowerSO-8 have an exposed die attach pad which
enhances the thermal conductivity enabling high power application.
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
12/19
STCS1A
Application information
– LEDs current: 500 mA;
– Package: DFN8 3x3 mm;
– T = 50°C;
A
In this case V
= 12 - 3 x 3.6 = 1.2 V
DRAIN
-3
-3
P = (1.2 - 0.1) x 0.5 + 12 x 0.5 x 10 = 0.55 + 6 x 10 = 556 mW
D
The junction temperature will be:
T = 37.6 x 0.556 + 50 = 70.9 °C
J
The following pictures show the maximum power dissipation according to the ambient
temperature for both packages:
Figure 16. Maximum power dissipation vs T
Figure 17. Maximum power dissipation vs T
A
A
for DFN8 3x3 mm
for PowerSO-8
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
3.00
2.50
2.00
1.50
1.00
0.50
0.00
RthJA = 38 [°C/W]
RthJA = 45 [°C/W]
PDMAX = (TJMAX-TA)/RthJA
PDMAX = (TJMAX-TA)/RthJA
25
35
45
55
65
75
85
95
105 115 125
25
35
45
55
65
75
85
95
105 115 125
[°C]
[°C]
13/19
Package mechanical data
STCS1A
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.
14/19
STCS1A
Package mechanical data
DFN8 (3x3 mm) mechanical data
mm.
mils.
Dim.
Min.
Typ.
0.90
0.02
0.70
0.20
0.23
3.00
2.38
3.00
1.64
0.50
0.40
Max.
1.00
0.05
Min.
Typ.
35.4
0.8
Max.
39.4
2.0
A
A1
A2
A3
b
0.80
31.5
27.6
7.9
0.18
2.23
1.49
0.30
0.30
2.48
1.74
0.50
7.1
9.1
11.8
97.7
68.5
19.7
D
118.1
93.7
118.1
64.6
19.7
15.7
D2
E
87.8
58.7
11.8
E2
e
L
15/19
Package mechanical data
STCS1A
PowerSO-8 mechanical data
mm.
inch.
Typ.
Dim.
Min.
Typ.
Max.
Min.
Max.
A
1.70
0.067
0.006
0.142
0.020
0.010
0.197
0.126
0.244
0.157
0.099
A1
A2
b
0.00
1.25
0.31
0.17
4.80
2.24
5.80
3.80
1.55
0.15
0.00
0.049
0.012
0.007
0.189
0.088
0.228
0.150
0.061
0.51
0.25
5.00
3.20
6.20
4.00
2.51
c
D
4.90
3.10
6.00
3.90
2.41
1.27
0193
0.122
0.236
0.154
0.095
0.050
D1
E
E1
E2
e
h
0.25
0.40
0°
0.50
1.27
8°
0.010
0.016
0°
0.020
0.050
8°
L
k
ccc
0.10
0.004
7195016C
16/19
STCS1A
Package mechanical data
Tape & reel QFNxx/DFNxx (3x3) mechanical data
mm.
Typ.
inch.
Typ.
Dim.
Min.
Max.
180
Min.
Max.
7.087
0.519
A
C
12.8
20.2
60
13.2
0.504
0.795
2.362
D
N
T
14.4
0.567
Ao
Bo
Ko
Po
P
3.3
3.3
1.1
4
0.130
0.130
0.043
0.157
0.315
8
17/19
Revision history
STCS1A
10
Revision history
Table 6.
Document revision history
Revision
Date
Changes
19-Feb-2008
02-Jul-2008
1
2
Initial release.
Modified: Table 5 on page 6.
18/19
STCS1A
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