Features
STP4CMP
Low voltage 4-channel constant current
LED driver with charge pump
■ Operating voltage range: V
(opr) = 2.7 V to
CC
5.5 V
■ Full RGB function support
■ 4-channel LED driver with individual ON/OFF
control directly from input pins
■ Individual programmable output current for the
4 channels through 4 external resistors with a
max. capability of 30 mA
■ Absolute output current accuracy of max. ±7%
and channel-to-channel mismatch of max.
±
4%
■ Selectable charge pump enable/disable
■ Thermal protection
■ Small QFN20 (1.8 x 3.2 mm) package
Applications
■ Mobile phone display backlighting
■ RGB LED indicator drivers
Description
QFN20
(1.8 x 3.2 mm)
provide brightness control. When enabled, the
charge pump, which uses a small ceramic bucket
capacitor between C1P and C1N, operates to
regulate the V
with a clamping voltage at typ.
OUT
5 V. The tiny QFN20 (1.8 x 3.2 mm) package
allows the device to be also used for applications
with space limitation.
The STP4CMP is a charge pump based 4channel LED driver designed for RGB illumination
or LCD display backlighting. The STP4CMP
works off a battery with an input voltage between
2.7 V - 5.5 V. The device generates regulated
current sinks with high absolute and channel-tochannel accuracy to drive up to 4 LEDs. It can
support LEDs with forward voltage as high as 3.8
V. The current sink for each channel can be set
with 4 individual external resistors. Each channel
is controlled independently. The PWM control can
be applied directly to the 4 EN (enable) pins to
Table 1. Device summary
Order code Package Packaging
STP4CMPQTR QFN20 Tape and reel
January 2012 Doc ID 15770 Rev 2 1/22
www.st.com
22
Contents STP4CMP
Contents
1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 Enable pin (EN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2 LED turn-on pin (ONx) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.3 Programmable output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.4 Charge pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.5 Thermal protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7 PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1 Recommended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2 Demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.3 Demonstration board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2/22 Doc ID 15770 Rev 2
STP4CMP Schematic
1 Schematic
Figure 1. Application schematic
GND
ON1
C
C
V
OUT
VCC
LED1
LED2
LED3
LED4
C2
C3
LED1
LED2
LED3
LED4
C1
C
OUT
AM00798V1
ON2
ON3
ON4
EN
I
SET1
R
SET1
I
SET2
R
SET2
I
SET3
R
SET3
I
SET4
R
SET4
GND
CP_Sel
Figure 1
shows the typical application diagram with the external components. To ensure an
optimal charge pump performance, it is highly recommended that the bucket capacitor, C1,
and the output capacitor, C
, to be placed as close as possible to the pins.
OUT
Table 2. Typical external components
Component Manufacturer Part number Value Size
MURATA GRM155R61A105KE15D
C1- C
OUT
TDK C1005X5R1A105MT
1 µF / 10 V 0402
MURATA GRM188R60J106ME84
C2
10 µF / 6.3 V 0603
TDK C1608X5R0J106MT
MURATA GRM155R60J104KA01D
C3
100 nF 0402
TDK C1005X5R1C104KT
R
LED1-4
1. R
(1)
SET1-4
(2)
: 649 Ω - 7.87 kΩ according to the desired output current from each channel.
SET1-4
2. LED1-4: typ. forward voltage of 3.8 V.
Tyco CPF0402B976RE1 976 Ω 0402
Note: All the above components refer to a typical application. Operation of the device is not limited
to the choice of these external components.
Doc ID 15770 Rev 2 3/22
Schematic STP4CMP
Figure 2. Block schematic
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4/22 Doc ID 15770 Rev 2
!-6
STP4CMP Pin configuration
2 Pin configuration
Figure 3. Pin connection (top through view)
340#-0
Table 3. Pin description
Pin number Symbol Name and function
1 ON1 LED1 enable
2 ON2 LED2 enable
!-6
3 ON3 LED3 enable
4 ON4 LED4 enable
5 EN Chip enable
6I
7I
8I
9I
SET1
SET2
SET3
SET4
LED1 max. current setting resistor
LED2 max. current setting resistor
LED3 max. current setting resistor
LED4 max. current setting resistor
10 GND Ground
11 CP_Sel Charge pump mode selection, ‘1’ => enable; ‘0’ => disable
12 LED4 4
13 LED3 3
th
LED current sink
rd
LED current sink
14 LED2 2nd LED current sink
15 LED1 1
16 V
17 V
18 C
CC
OUT
1P
st
LED current sink
Supply voltage
Charge pump output
Positive terminal of charge pump bucket capacitor
Doc ID 15770 Rev 2 5/22
Pin configuration STP4CMP
Table 3. Pin description (continued)
Pin number Symbol Name and function
19 C
Negative terminal of charge pump bucket capacitor
1N
20 GND Ground
6/22 Doc ID 15770 Rev 2
STP4CMP Maximum ratings
3 Maximum ratings
Table 4. Absolute maximum ratings
Symbol Parameter Value Unit
ON
; VCC;
1-4
EN; CP_Sel;
C1P; C1N;
VOUT Output voltage - 0.3 to +6 V
LED
; ISET
1-4
Supply voltage - 0.3 to +6 V
Current setting - 0.3 V to 2 V
1-4
Machine model ± 200
ESD
VHuman body model (MIL STD_883) ±1500
Charged device model ± 500
T
T
AMB
T
J
STG
Operating ambient temperature - 30 to 85 °C
Maximum operating junction temperature + 150 °C
Storage temperature - 65 to 150 °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 5. Recommended operating conditions
Val ue
Symbol Parameter
V
T
I
LED
T
pwm_ON
T
pwm_OFF
Supply voltage 2.7 - 5.5 V
CC
Operating temperature -40 - 85 °C
op
Current through each LED 2.5 - 30 mA
ON time of PWM signal at each ON
pin
OFF time of PWM signal at each ON
pin
Min. Typ. Max.
33 - µs
33 - µs
Unit
V
LED forward voltage - 3.8 V
fw
Table 6. Thermal data
Symbol Parameter Value Unit
(1)
R
thJA
1. This parameter corresponds to the PCB board, 4-layers with 1inch² of cooling area.
Junction to ambient thermal resistance 70 °C/W
Doc ID 15770 Rev 2 7/22
Electrical characteristics STP4CMP
4 Electrical characteristics
VCC=3.3V, VEN=V
= 649 Ω, C1 =1 µF, typical values are at TA=25°C, unless otherwise specified.
R
SET4
Table 7. Electrical characteristics
ON1=VON2=VON3=VON4=VCC
, V
CP_SEL
= VCC, R
SET1
= R
SET2
= R
SET3
Symbol Parameter Test condition Min. Typ. Max. Unit
V
CC
V
cp_clamp
Supply voltage 2.7 5.5 V
Charge pump clamp voltage
2.7 V ≤ VCC < 3.1 V;
V
V
I
CP_sel
> 3.1 V; V
CC
≤ 120 mA
OUT
= V
CC; IOUT
CP_sel
≤ 40 mA
= V
CC;
5
5
From CP_sel low to high
T
cp_start
Charge pump startup time
transition to CP reaches
10 ms
steady-state at 5 V
R
I
LED1,2,3,4
Δ I
LED
V
IH
V
IL
= 649 Ω at V
setx
> 3.1 V
V
LED sink current for each
channel
Output current error
between each channel
CC
= 7.87 kΩ at
R
setx
V
= 0.9 V; VCC ≥ 3.1 V
LEDx
R
set1=Rset2=Rset3=Rset
TA = 25 °C
High level input voltage 2.0 V
Low level input voltage 0.8 V
V
ON1=VON2=VON3=VON4
ND; no load; V
(charge pump disabled);
V
R
=GND,
CP_SEL
set1=Rset2=Rset3=Rset4
LEDx
CC
=0.9 V;
=5.5 V
27.9 30 32.1 mA
2.33 2.5 2.68 mA
±1 ±4 %
=G
3.6
=
7.87 kΩ
=
V
V
ON1=VON2=VON3=VON4
ND; no load; V
(charge pump disabled);
V
R
I
CC
Supply operating current
649 Ω
V
=GND,
CP_SEL
set1=Rset2=Rset3=Rset4
ON1=VON2=VON3=VON4
ND; no load; V
(charge pump disabled);
V
CP_SEL=VCC
7.87 kΩ
V
ON1=VON2=VON3=VON4
ND; no load; V
(charge pump disabled);
V
CP_SEL=VCC
R
set1=Rset2=Rset3=Rset4
649 Ω
8/22 Doc ID 15770 Rev 2
=5.5 V
CC
=3.3 V
CC
, R
set1=Rset2
=3.3 V
CC
,
=G
1.7
=
mA
=G
4.5
=
=G
17.2
=
STP4CMP Electrical characteristics
Table 7. Electrical characteristics (continued)
Symbol Parameter Test condition Min. Typ. Max. Unit
I
SHUTDOWN
T
SD
T
HS
Supply current during
power-down
VEN=V
ON1=VON2=VON3=VON
=V
4
CP_SEL
= 0 V
5µA
Thermal shutdown 150 °C
Thermal shutdown
hysteresis
15 °C
Doc ID 15770 Rev 2 9/22
Detailed description STP4CMP
5 Detailed description
The STP4CMP is a charge-pump-based 4-channel LED driver designed for RGB
illumination or LCD display backlighting, using constant current topology. Each of the 4
channels can be controlled independently. When ONx is pulled high, a constant current is
sunk into the LEDx pin when a LED is connected. This constant current is defined or
programmed by the value of the resistor at I
5.1 Enable pin (EN)
The active high enable input pin is used to shut down the whole device. When this pin is
pulled low, the device enters into shutdown mode with only 5 µA max. current consumption.
An internal pulled down of 300 kΩ is present at this pin.
5.2 LED turn-on pin (ONx)
When the EN pin is pulled high, the STP4CMP provides the flexibility to control the turningON/OFF on the 4 channels independently through the 4 active high ON pins. To control the
brightness of each LED channel, it is possible to drive the selected ON pin with a PWM
signal with a frequency up to a minimum T
is present at these pins.
SETX
ON/TOFF
pin.
of 33 µs. An internal pull-down of 300 kΩ
5.3 Programmable output current
The LED currents at the 4 channels are programmed individually through a resistor
connected from I
and the LED current (I
set1
, I
, I
set2
LED
, I
set3
) is governed by this equation:
Equation 1
R
= 16 * (1.22 / I
SET
LED
)
5.4 Charge pump
The STP4CMP charge pump can be disabled or enabled according to the CP_sel pin.
When enabled (CP_sel is high), the charge pump provides a clamping voltage of typ 5.0 V
to ensure enough headroom to drive the LEDs. An internal pull-down of 300 kΩ is present at
this pin.
The charge pump can be disabled by pulling low the CP_sel pin, based on the V
forward voltage of the LEDs used. This allows the connection of V
drive the external LEDs.
At V
drawn from it (at V
At 2.7 ≤ V
current drawn from it (at V
3.1 V, the charge pump is able to maintain regulation at 5 V when the total current
CC
< 3.1 V, in order for the charge pump to maintain regulation at 5 V, the total
CC
pin) is ≤ 120 mA.
OUT
pin) must be lowered to ≤ 40 mA.
OUT
to ground. The relationship between the resistor (R
set4
directly to V
CC
CC
OUT
and
to
SET
)
10/22 Doc ID 15770 Rev 2
STP4CMP Detailed description
5.5 Thermal protection
The thermal protection circuit ensures device shutdown when it is overheated (for example,
due to an output short-circuit) to typ. 150 °C. The device resumes normal operation when
the temperature drops by 15 °C from the thermal shutdown threshold.
Doc ID 15770 Rev 2 11/22
Typical performance characteristics STP4CMP
6 Typical performance characteristics
Figure 4. Eff. vs.VIN, I
100
95
90
85
80
75
70
65
60
Eff [%]
55
50
45
40
35
30
2.7 3.0 3.2 3.5 3.7 4.0 4.2 4.5 4.7 5.0 5.2 5.5
Figure 5. Eff. vs.V
100
Eff [%]
, I
IN
95
90
85
80
75
70
65
60
55
50
45
40
35
30
2.7 3.0 3.2 3.5 3.7 4.0 4.2 4.5 4.7 5.0 5.2 5.5
OUT
OUT
= 10 mA
= 60 mA
VIN[V]
VIN[V]
AM10404V1
EFF
Iin
AM10405V1
EFF
Iin
29
27
25
23
21
19
17
15
260
250
240
230
220
210
200
[mA]
IN
I
[mA]
IN
I
Figure 6. V
OUT
vs.V
IN
5.00
4.95
4.90
4.85
4.80
4.75
[V]
OUT
4.70
V
4.65
4.60
4.55
4.50
2.6 2.9 3.1 3.4 3.6 3.9 4.1 4.4 4.6 4.9 5.1 5.4
12/22 Doc ID 15770 Rev 2
AM10406V1
VIN[V]
STP4CMP Typical performance characteristics
Figure 7. PWM modulation CH1-2
Figure 8. Output ripple
Doc ID 15770 Rev 2 13/22
PCB layout STP4CMP
7 PCB layout
7.1 Recommended
The STP4CMP is a charge pump power device so it requires a proper PCB layout in order to
obtain the necessary stability and optimize line/load regulation and output voltage ripple.
Input, output, and boost capacitors must be as close as possible to their relative pins.
Figure 9. Top layer
Figure 10. Bottom layer
14/22 Doc ID 15770 Rev 2
STP4CMP PCB layout
Figure 11. Top overlay
7.2 Demonstration board
Figure 12. Demonstration board
Doc ID 15770 Rev 2 15/22
PCB layout STP4CMP
7.3 Demonstration board schematic
Figure 13. Demonstration board schematic
VCC
VCC
20
VOU T
LED1
LED2
LED3
LED4
11
VCC
1
2
P1
U1
STP4CMP
GND
19
C1N
C1N
C1P
18
C1P
VOU T
17
16
VCC
VCC
LED1
15
LED2
14
LED3
13
LED4
12
2
LED4 LED3 LED2 LED1
1
C2
C3
10µF
100n
C1
1µF
12121
P6 - P10 heade r are used to load o utputs when no
1
2
LED is populated.
P6
1
2
P7
1
2
P8
1
2
VOU T
C4
1µF
2
P9
1
2
P10
Pulldown resistors R1 -R6 to gua rant e e c or re c t
function when no jump er is placed.
VCC
1
3
VCC
1
3
VCC
1
3
1
2
P3
1
2
P5
For efficiency measurements, pu ll down s should be
removed to measure correct DUT input curren t,
otherwise pulldown resistors current would affec t
the result.
2
VCC
1
JP3
3
JP4
2
VCC
1
JP5
3
JP6
2
JP1
1
2
P2
1
2
P4
VCC
1
3
JP2
R3
10k
2
2
2
CP_SEL
R4
10k
R5
10k
R6
10k
R1
10k
1kR71kR81kR91k
ON1
1
ON1
ON2
2
ON2
ON3
3
ON3
ON4
4
ON4
EN
5
EN
ISET1
6
ISET1
ISET2
7
ISET2
ISET3
8
ISET3
ISET4
9
ISET4
CP_SEL
GND
10
R10
R2
10k
Pulldown resistors R7 -R 1 0 are set resistors for
each channel. Needed to be changed for different
output current set
up.
AM10407v1
16/22 Doc ID 15770 Rev 2
STP4CMP Package mechanical data
8 Package mechanical data
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.
Figure 14. Package outline for QFN20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm
Doc ID 15770 Rev 2 17/22
Package mechanical data STP4CMP
Table 8. Mechanical data for QFN20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm
Millimeters
Symbol
Min. Typ. Max.
A 0.45 0.50 0.55
A1 0 0.02 0.05
A3 0.127
b 0.15 0.20 0.25
D 3.15 3.20 3.25
E 1.75 1.80 1.85
e 0.40
L 0.35 0.40 0.45
Figure 15. Footprint recommendations for QFN20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm
1. Drawing not to scale.
2. Dimensions are in millimeters.
18/22 Doc ID 15770 Rev 2
STP4CMP Package mechanical data
Figure 16. Carrier tape for QFN20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm
$0Y
Doc ID 15770 Rev 2 19/22
Package mechanical data STP4CMP
Figure 17. Reel information for QFN20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm
1. Drawing not to scale.
2. Dimensions are in millimeters
20/22 Doc ID 15770 Rev 2
STP4CMP Revision history
9 Revision history
Table 9. Document revision history
Date Revision Changes
09-Jun-2009 1 Initial release.
24-Jan-2012 2
Document status promoted from preliminary data to datasheet.
Added
Section 7 on page 14
.
Doc ID 15770 Rev 2 21/22
STP4CMP
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22/22 Doc ID 15770 Rev 2
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