SITI PC112

PC112/PC113
Version
: A.001
Issue Date : 2004/10/01
File Name : SP-PC112/PC113-A.001.doc
Total Pages: 14
Step Up Converter for White LED Driver
新竹市科學園區展業一路 9 號 7 樓之 1
SILICON TOUCH TECHNOLOGY INC.
9-7F-1, Prosperity Road I, Science Based Industrial Park,
Hsin-Chu, Taiwan 300, R.O.C.
Tel：886-3-5645656
Fax：886-3-5645626
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
General Description
PC112/PC113 is a compact, high-efficiency step-up DC-DC converter which drives
2-6 series white LEDs with constant current from 3V to 5V. Extremely low shutdown
power supply current ensures the high efficiency of battery system. The PC113 works
at 500KHz, allowing the application of tiny external components. Low feedback voltage
and hence minimal input current from the battery extends battery life.
Built-in N-channel power switches optimize the layout area of PCB. Since
PC112/PC113 drives series LEDs, it regulates the light intensity uniformly. With a single
external resistor or PWM signal, users can easily set the LED current and LED
brightness.
While output loading is open, likes the case of LEDs failure, the duty cycle of the
DC-DC converter will increase rapidly, causing high output voltage to damage the
circuit. To avoid this situation, a Zener diode should be connected to the DC-DC
converter’s output to clamp the output voltage in most applications. However, PC113
has built-in the over-voltage protection circuit to protect the output circuit and thus
eliminates the need of the external Zener diode.
PC112/PC113 is also characterized of the soft-start feature, which limits the inrush
current. It is available in Thin-SOT type package.
Features
1.
2.
3.
4.
5.
Typical 85% efficiency
No external power switch
Low shutdown supply current
Low feedback voltage
Drives 6 white LEDs 20mA from working voltage 2.0V
6. ±4 % LED output current accuracy
7. Over voltage protection circuit build in(PC113)
8. Soft-start circuit build in
9. Thin 6-pin SOT23-6 package
Application
1.
2.
3.
4.
5.
White LED Display Backlighting
Cellular Telephones
Personal Digital Assistant
Digital Cameras
Portable Machine
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Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
Block Diagram
FB
VSS
2
3
AMP
Soft
Start
CMP
PreDriver
1
LX
FB
VSS
2
3
AMP
LX
+
Pre
Driver
0.1V
CMP
1
0.5V
OVP
Clock
Genertor
5
5
VDD
Soft
Start
Control
Logic
4
OVP
Clock
Genertor
Control
Logic
5
EN
4
VDD
PC113
EN
PC112
Pin Descriptions
Pin No
PIN NAME
Descriptions
PC113 PC112
1
1
LX
2
2
VSS
3
3
FB
Feedback pin
4
4
EN
Enable pin
5
6
5
1
LX
2 VSS
3
FB
SiTI
PC113
Connect inductor to battery
Ground pin
OVP
Over voltage protection
VDD
Input voltage supply pin
1
VDD 6
2 VSS
OVP 5
EN
LX
4
3
FB
SiTI
VDD 5
PC112
EN
4
TopView
-2 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
Absolute Maximum Ratings
Parameter
Supply Voltage
Symbol
VDD
Rating
5.5
Unit
V
LX Voltage
VLX
24
V
EN Voltage
Power Dissipation
VEN
Pd
5.5
2.5
V
mW
Storage Temperature
Tstg
-65~140
o
C
-40~120
o
C
160
o
C
Operating Temperature
Topr
Junction Temperature
TJ
Electrical characteristics, VDD=3.6V,
PARAMETER
SYMBOL
Ta = 25 oC . (unless otherwise specified)
CONDITION
MIN
TYP
MAX
Unit
Operating Input Voltage
VDD
2.8
3.6
5
V
FB PIN Voltage
VFB
85
95
105
mV
FB Vol. Temp. Coefficient
TFB
Switch-on Resistance
RSW
Switch Max On-time
TON
Maximum Duty Cycle
DMAX
Switching Frequency
FSW
Efficiency
Supply Current
ILED = 20mA
1.4
450
η
+92
µV/°C
1.5
Ω
1.5
500
1.6
µS
80
%
550
KHz
85
%
IDD
VEN=High
1
mA
IDDQ
VEN=Low
0.1
µA
VEN=High
0.2
mA
VEN=Low
10
nA
23
V
Shutdown Input Current
IEN
*Over voltage protection
VP
*Note1 : Only PC113 build this function
-3 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
Typical application circuit
VIN
2.8 to 5.0V
L1
6.8uH
IIN
D1
MBR0520
R1
C1
4.7uF
22Ω
C2
4.7uF
Zener
LX
VDD
SiTI
FB
PC112
ON
R3
1KΩ
EN
OFF
R2
5.6Ω
VSS
Fig. 1
VIN
2.8 to 5.0V
C3
1uF
Application circuit of PC112
L1
6.8uH
IIN
D1
MBR0520
R1
C1
4.7uF
22Ω
C2
4.7uF
White
LED
x3
LX
VDD
SiTI
OVP
ILED
20mA
C3
1uF
PC113
ON
OFF
FB
EN
VSS
R2
5.6Ω
Fig. 2
Application circuit of PC113
-4 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
Typical performance characteristics
R1=22Ω, L1=6.8µH, C1=4.7µF, C2=4.7µF, C3=1µF, Schottky diode VF=0.18, Ta = 25 oC ,
(unless otherwise specified)
Efficiency vs Load current
0.89
0.88
0.87
VIN=4.2V
VIN=4.2V
0.87
0.86
VIN=3.6V
Efficiency (%)
0.85
VIN=2.85V
0.84
0.83
VIN=3.6V
0.85
0.84
VIN=2.85V
0.83
0.82
0.82
2LEDs
0.81
5
10
25
0.8
30
Efficiency vs Load current
0.106
0.85
0.104
Feedback voltage (V)
0.108
0.86
VIN=4.2V
0.84
VIN=3.6V
0.83
0.82
0.81
VIN=2.85V
0.8
0.78
15
20
Load current (mA)
25
30
Feedback voltage vs Load current
4x LEDs
3x LEDs
0.102
2x LEDs
0.1
0.098
0.096
0.092
10
15
20
Load current (mA)
25
0.09
30
Efficiency vs Temperature (High Load)
85
10
0.094
4LEDs
5
5
0.11
0.87
0.79
3LEDs
0.81
15
20
Load current (mA)
0.88
5
10
15
20
Load current (mA)
25
30
Efficiency vs Temperature (Light Load)
84
83
84
VIN=2.85V
82
83
VIN=4.2V
82
Efficiency (%)
Efficiency (%)
Efficiency (%)
Efficiency (%)
0.86
0.8
Efficiency vs Load current
0.88
VIN=3.6V
81
VIN=2.85V
80
VIN=3.6V
80
VIN=4.2V
79
78
3 WLEDs, 25mA
3 WLEDs, 5mA
79
78
-40
81
77
-20
0
20
40
60
80
Temperature (degree)
100
120
140
-5 -
76
-40
-20
0
20
40
60
80
Temperature (degree)
100
120
140
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
Typical performance characteristics (cond.)
Feedback voltage vs Load current
0.1
Frequency vs Temperature
560
540
0.098
4x LEDs
Frequency (KHz)
Feedback voltage (V)
520
0.096
3x LEDs
0.094
2x LEDs
0.092
500
480
460
0.09
0.088
440
5
10
15
20
Load current (mA)
25
420
30
-20
0
20
40
60
Temperature (degree)
80
100
120
NOTE1 :The white LED forward voltage is about 3.6V, so PC112/PC113 could drive up to 6
series white LEDs.
NOTE2 : To chose D1(Schottky diode), it must has fast switch characteristics and low
forward voltage. We recommend the MBR0520in this application.
NOTE3 : The ripple of input voltage could be minimized with C1. Thus, a large value of
capacitor C1 is suggested. With the application of a RC-filter (R1 and C2) to VDD
pin, the stability of circuit is enhanced. The ripple of output voltage also could be
improved with C3. In most designs, the low ESR (equivalent series resistance)
capacitors are desirable, like multi-layer capacitor. A 1uF to 2.2uF output
capacitor is sufficient for most applications.
NOTE4 : ILED =
0.095
R2
(A)
-6 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
Application Information
Reference Fig.1 ,condition: Zener=15V, Ta = 25 oC , unless otherwise specified
LX
VDD
(AC)
VO
IIN
LX
VO
VO
EN
EN
IIN
IIN
VFB
VO
EN
IIN
-7 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
General Description
Bias current setting
The PC112/PC113 is a DC/DC converter which provides a regulated current output
from a VDD input of DC 2.8V to 5.0V. Regulating the LED current can be achieved by
setting the resistor of FB pin to ground. So the value of the current setting resistor R2
could be set by:
R2=
0.095
I LED
(Ω)
Brightness control
The brightness control can be achieved by applying a PWM control signal to EN
pin or by varying the current setting resistor R2, shown as follows.
PC113
PC113
EN
PC113
FB
4
5
PWM
RMIN
FB
4
RINCR
PWM
To
LEDs
RA
RB
R2
VADJ
Fig. 3
Fig. 4
Fig. 5
We could apply a digital PWM signal (100Hz~3KHz) to EN pin (Fig. 3) to generate
a LED current waveform identical to that of the PWM signal waveform. The average
output LED current is calculated:
0.095
ILED = R 2 x Duty of PWM
(A)
Another control method is to vary the value of the current setting resistor (Fig. 4).
ILED =
RMIN × RINCR
0.095
which
R2
=
RMIN + RINCR , PWM is High
R2
(A)
A DAC can also be applied for brightness control, which is shown in Fig. 5. If VADJ
-8 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
(output of a DAC or Ambient Light Sensor) increases, the output voltage will decrease.
For example, RA=6.2KΩ, RB=82KΩ, VADJ = 4V, VFB1 will set to 0.05V, so the LED’s
current will be half .
Open circuit protection (PC113 only)
When the LEDs are disconnected from the circuit or the LEDs fail, PC113 will
switch to maximum duty cycle. This situation results in a high output voltage and may
cause the LX pin voltage to exceed its maximum rating of 24V and thus damages
output circuit. Normally, a Zener diode is applied to clamp the high voltage; however,
PC113 has built-in the over-voltage protection circuit, and thus no external component
is required.
Recommended PCB layout
1. C2 is placed as close to PC112/113 as possible.
2. Minimize the length and area of all traces connecting to LX pin.
3. The power path : VDD
L1
LX
D1
C3 should be kept as short as
possible to avoid EMI.
4. Fig. 6 shows the exemplary test board layout. (Reference page4. typical
application circuit )
Fig. 6
-9 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
1.9
mm
0.35mm
Recommended solder pad
1.6mm
3.1 mm
Fig. 7
-10 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
Package Specification (SOT23-6)
C
E
H
L
e
θ1
D
A2
A
A1
b
SYMBOL
Dimensions in Millimeters
MIN
NOM
MAX
A
A1
1.00
0.00
1.10
－
1.30
0.10
A2
b
C
D
E
e
0.70
0.35
0.10
2.70
1.40
－
0.80
0.40
0.15
2.90
1.60
1.90(TYP)
0.90
0.50
0.25
3.10
1.80
－
H
L
2.60
0.37
2.80
－
3.00
－
θ1
1°
5°
9°
-11 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
Package Specification (SOT23-5)
C
E
H
L
e
θ1
D
A2
A
A1
b
SYMBOL
DIMENSIONS IN MILLIMETERS
MIN
NOM
MAX
A
A1
1.00
0.00
1.10
－
1.30
0.10
A2
b
C
D
E
e
0.70
0.35
0.10
2.70
1.40
－
0.80
0.40
0.15
2.90
1.60
1.90(TYP)
0.90
0.50
0.25
3.10
1.80
－
H
L
2.60
0.37
2.80
－
3.00
－
θ1
1°
5°
9°
-12 -
Version：A.001
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
PC112/PC113
The products listed herein are designed for ordinary electronic applications, such as electrical
appliances, audio-visual equipment, communications devices and so on. Hence, it is advisable
that the devices should not be used in medical instruments, surgical implants, aerospace
machinery, nuclear power control systems, disaster/crime-prevention equipment and the like.
Misusing those products may directly or indirectly endanger human life, or cause injury and
property loss.
Silicon Touch Technology, Inc. will not take any responsibilities regarding the misusage of
the products mentioned above. Anyone who purchases any products described herein with the
above-mentioned intention or with such misused applications should accept full responsibility
and indemnify. Silicon Touch Technology, Inc. and its distributors and all their officers and
employees shall defend jointly and severally against any and all claims and litigation and all
damages, cost and expenses associated with such intention and manipulation.
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Version：A.001