STCS1PHR [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： | STCS1PHR |
| 厂家： | 
ST |
| 描述： | 1.5 A max constant current LED driver |
| 文件： | 总17页 (文件大小：436K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
STCS1
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 (3x3mm)
Power SO-8
■ LED disconnection diagnostic
Applications
■ Supplying LEDs with constant current for
The current is set with external resistor up to 1.5
A with a 10% precision; a dedicated pin allows
implementing PWM dimming.
varying input voltages
■ Low voltage lighting
■ Small appliance LED lighting
■ Car LED lights
An open-drain pin output provides information on
load disconnection condition.
Description
The STCS1 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
STCS1PUR
STCS1PHR
DFN8 (3mm x 3mm)
Power SO-8
3000 parts per reel
2500 parts per reel
October 2007
Rev. 5
1/17
www.st.com
17
STCS1
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10
2/17
STCS1
1
Application diagram
Application diagram
Figure 1.
Typical application diagram for 0.5 A LED current
VIN
4.5V to 40V
(*)
RIN
100Ohm
CBYP
0.1µF
VCC
PWM
EN
DRAIN
ON
ON
STCS1
CDRAIN
0.47µF
OFF
OFF
DISC
FB
GND
RFB
0.2Ohm
Load disconnection
(Open Drain output)
(*) The RIN resistor must be inserted when dVCC/dt is higher than 10 V/µs
3/17
Pin configuration
STCS1
2
Pin configuration
Figure 2.
Pin connections (top view)
PowerSO-8
DFN8
Table 2.
Pln 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.
Not connected
DISC
Exp-pad
Load disconnection flag (open drain)
Internally connected to ground.
4/17
STCS1
3
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 accoring the following formula:
TJ = TA + (PD x RthJA). See Figure 12. and Figure 13. 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.
5/17
Electrical characteristics
STCS1
4
Electrical characteristics
Table 5.
Electrical characteristics
(V = 12 V; I = 100 mA; T = -40°C to 85°C; V
= 1 V; C
= 1 µF; C = 100 nF
BYP
CC
O
A
DRAIN
DRAIN
typical values are at T = 25°C, unless otherwise specified)
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 = 100 mA; VDRAIN = 1 V
-1
+1
%
VFB
Feedback voltage
All the current range
On Mode
90
100
450
110
650
mV
Quiescent current (measured on
VCC pin)
ICC
µA
Shutdown Mode;
1
VCC = 5 to 40 V
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
Shutdown; VDRAIN = 40 V
VPWM rising, VCC = 12 V
VPWM falling, VCC = 12 V
ISINK = 5 mA
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
V
DISC = 5 V
µA
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
50
µA
VPWM = 40 V
100
Note:
All devices 100% production tested at T = 25°C. Limits over the operating temperature
A
range are guaranteed by design.
6/17
STCS1
5
Timing
Timing
Figure 3.
PWM and output current timing
PWM
90%
10%
Current
TD
Trise
TD Tfall
Figure 4.
Block diagram
7/17
Typical performance characteristics
STCS1
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
8/17
STCS1
Detail description
7
Detail description
The STCS1 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 1.5 A can be set according to the resistor value, the resulting
output current has a tolerance of 10%.
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 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 TD (see Figure 3.).
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.
7.4
Diagnostic
When STCS1 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 pulled
DRAIN
DRAIN
low regardless the PWM pin status. This information can be used by the system to inform
that some problem happens in the LEDs.
9/17
Application information
STCS1
8
Application information
8.1
Reverse polarity protection
STCS1 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
+
8.2
Thermal considerations
The STCS1 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 circuit
thJA
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
– LEDs current: 500mA;
10/17
STCS1
Application information
– 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 12. Maximum power dissipation vs T
Figure 13. Maximum power dissipation vs T
A
A
for DFN8 3x3mm
for PowerSO-8
2.50
2.00
1.50
1.00
0.50
0.00
2.00
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
25
35
45
55
65
75
85
25
35
45
55
65
75
85
[°C]
[°C]
11/17
Package mechanical data
STCS1
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.
12/17
STCS1
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
13/17
Package mechanical data
STCS1
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
14/17
STCS1
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
15/17
Revision history
STCS1
10
Revision history
Table 6.
Document revision history
Revision
Date
Changes
10-Apr-2007
07-May-2007
1
2
Initial release.
PowerSO-8 mechanical data has been updated and the RthJC for PowerSO-8
value on Table 4. is changed.
24-May-2007
27-Sep-2007
02-Oct-2007
3
4
5
Change value CBYP 0.1µF ==> 1 µF on Figure 1. typical application.
Add RIN on Figure 1. application diagram.
Figure 1. updated.
16/17
STCS1
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