EV5103 Datasheet, PDF (2/4 Pages) Global Mixed-mode Technology Inc – G5103 White LED Demo Board V1.0

Global Mixed-mode Technology Inc.
EV5103-10
Components List
Designation
R1
R2
R3
R4
C1
C2
C3
C4
C5
L1
D1
U1
U2
U3
SW1~3
LED1~4
Qty
Value& P/N
Description
1 27Ω_1%
Current Sense Resistor
1 120KΩ_1%
Feedback Resistor (recommend)
1 240KΩ_1%
PWM Dimming Control Bias Resistor
1 620KΩ_1%
PWM Dimming Control Mixer Resistor
1 4.7µF
Input Capacitor
1 0.1µF
Output Capacitor
1 1µF
Input Capacitor
1 1µF
Output Capacitor
1 0.1µF
Bypass Capacitor
1
10µH/0.5A IDC
(LQH32CN100K31)
10µH/0.5A IDC
(976AS-100M)
Inductor
Inductor
1 0.5A/30V(MBR0530) Schottky Diode
1 G5103
Micro Power Step-up DC/DC Converter
1 G914C
1 PIC12C509A
Mirco power LDO regulator. VOUT=3.0V
8 bits micro-controller
3
Push button switch
4 NSCW100
White LED
Vendor
Std
TAIYO YUDEN
MURATA
TOKO
ON Semi
Global Mixed-Mode Technology
http://www.gmt.com.tw
Miocrochip
Std
NICHIA corporation
Circuit Description
The demo board is configured as a constant current supply. Current regulation is accomplished by regulating
the voltage across a current sense resistor R1. For dimming the LEDs is to inject a pulse width modulated
(PWM) voltage for analog dimming. With this method, the PWM control voltage is converted to its equivalent
analog control voltage. The demo board is designed so that the negative duty cycle from 0% to 100% varies
the LED current from 0mA to 20mA. The output current increases as the duty cycle increases. Use the
equation below to calculate the correctly resistor values.
V_BAT:
V_BIAS:
R1:
Li-Ion battery power input, bypass to ground with a 4.7µF MLCC capacitor.
+3.0VDC provide a PWM dimming DC bias voltage. It is generated by G914C from V_BAT.
is LED current sense resistor. R1= 0.60V / ILED,MAX = 0.60V / 20mA = 30Ω
R2:
is feedback resistor, 120KΩ is recommended.
R4:
is PWM dimming control mixer resistor. The value is depended on PWM dimming control signal
amplitude. R4= (V_H - V_L) / (0.6V / 120KΩ). (maximum value, a little small value could be used)
For 3.0V PWM control signal: R4= 3V / (0.6V / 120KΩ) = 600KΩ.
For 3.3V PWM control signal: R4= 3.3V / (0.6V / 120KΩ) = 660KΩ.
For 5.0V PWM control signal: R4= 5V / (0.6V / 120KΩ) = 1MΩ.
R3:
is PWM dimming control bias resistor. The value is depended on VBIAS voltage.
R3=( VBIAS– V_FB) /[(0.6V/120 KΩ)+(VFB / R4)].
For 3VDC VBIAS:= (3.0V – 1.2V) / [(0.6V/120 KΩ)+(1.2V / 600 KΩ)] = 257 KΩ.
For 3.3VDC VBIAS:= (3.3V – 1.2V) / [(0.6V/120 KΩ)+(1.2V / 660 KΩ)] = 308 KΩ
For 5VDC VBIAS:= (5.0V – 1.2V) / [(0.6V/120 KΩ)+(1.2V / 1000 KΩ)] = 612 KΩ
After choose suitable resistors, designer should check I_LED again.
Jan 21, 2003
TEL: [phone]
http://www.gmt.com.tw
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