BD6155FVM
Communication ICs
DC/DC converter for LCD back light
BD6155FVM
BD6155FVM is an ideal IC to drive white LED used for the LCD back light of cellular phones, and PDA etc.
This IC incorporates charging pump step-up circuit to drive white LED with high V
F
. It also integrates a driver to drive
white LED with 4-step constant current. Only one external resistor can set the current value.
!Applications
Small portable appliances, such as cellular phones, PHS, PDA
Battery-powered equipments using the white LED.
!Features
1) Built-in charging pump step-up circuit.
2) Built-in constant current driver for LED. (Current value : 4 steps variable)
3) Ultra small MSOP8 package. (Height 0.9mm Max.)
!
Absolute maximum ratings
(Ta=25°C)
Parameter
Maximum supply voltage
Maximum input voltage
Power dissipation
Symbol
V
BAT
V
IN
Pd
Topr
Tstg
Limits
−0.3~+6.0
−0.3~+6.0
350
∗
−25~+75
−55~+125
Unit
V
V
mW
°C
°C
Operating temperature
Storage temperature
∗
Reduce to 3.5mW/°C when Ta=25°C or above.
!
Recommended operating conditions
(Ta=25°C)
Parameter
Power supply
Symbol
V
BAT
Min.
2.9
Typ.
−
Max.
5.5
Unit
V
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BD6155FVM
Communication ICs
!
Block diagram
CURRENT1
1
CURRENT
CONT
8
CHARGE
PUMP
DRIVER
7
V
BAT
CURRENT2
2
C
STBY
3
6
GND
LEDS
4
5
LED
!
Pin descriptions
Pin No.
1
2
3
4
5
6
7
8
Pin Name
CURRENT1
CURRENT2
STBY
LEDS
LED
GND
C
VBAT
Function
Fixed current setup pin1.
Fixed current setup pin2.
Stand-by pin (High:Operation, Low:No operation)
LED driver current pin (Fixed current sink pin)
LED cathode connection pin for charge pump
Ground
Capacitor connection pin for charge pump
Power supply voltage input pin
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BD6155FVM
Communication ICs
!
Electrical characteristics
(unless otherwise noted, Ta=25°C, VBAT=3.6V, STBY=3.6V)
Parameter
<LED+Charge pump block>
Circuit current
Standby current
<Fixed current driver for LED>
LED max drive current
NMOS ON resistance
Current control setup voltage 1
Current control setup voltage 2
Current control setup voltage 3
Current control setup voltage 4
Fixed current setup pin Hi
control voltage
Low
<Charge pump>
Oscillator frequency
Output voltage 1
Output voltage 2
Stand-by pin pull down resistor
Stand-by pin control
voltage
Active
Stand-by
fosc
VDC1
VDC2
RSTBY
V
IH
V
IL
−
4.8
4.4
250
2.0
−0.3
120
5.6
4.8
400
−
−
−
−
−
700
−
0.3
kHz
V
V
kΩ
V
V
VBAT=3.6V, I
O
=80mA charge pump output monitor RB521-S30 use
VBAT=3.2V, I
O
=60mA charge pump output monitor RB521-S30 use
ILEDMAX
Ron7
∆VLED1
∆VLED2
∆VLED3
∆VLED4
V
IH
V
IL
−
−
184
131
89
42
2.0
−0.3
−
3
205
155
105
55
−
−
80
7
226
179
121
68
−
0.3
mA
Ω
mV
mV
mV
mV
V
V
Drive current 80mA
CURRENT2=High, CURRENT1=High
CURRENT2=High, CURRENT1=LOW
CURRENT2=LOW, CURRENT1=High
CURRENT2=LOW, CURRENT1=LOW
I
Q
1
I
Q
2
−
−
0.3
−
1.0
5
mA
µA
No load
No load, STBY=0V
Symbol
Min.
Typ.
Max.
Unit
Conditions
This product is not designed for protection against radioactive rays.
!
Measurement circuit
1µF
1
V1
A
AM1
CURRENT1
VBAT
8
SWD1
OPEN
D1
2
7
A
AM8
V8
7
SW7 1
C1
ON
OPEN
1
AM72
A
V72
SW72
2
V
F
2
V2
A
AM2
CURRENT2
C+
7
3
IS72
VM72
FM72
D2
SWD2
OPEN
AM3
5
3
V3
A
STBY
GND
6
ON
OPEN
1
A
SW52
2
V
SW4
1
2
3
1
4
LEDS
LED
5
SW5
2
5
SWO1
OPEN
C2
ON
OPEN
SWO3
SWO2
ISO1
V
AM52
V52
IS52
VM52
R=2.7Ω R=20KΩ
3
ON
V
SW4B
ON
AM4
V
V
VM4
VO1
VA01
Fig.1
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BD6155FVM
Communication ICs
!
Circuit operation
1) Charge pump driver
Charge pump is consisted capacitor pin (pin7), external schotky diodes and capacitors.
Output voltage at no loading is 2VBAT-2VF. (VF is as same as schotky’s VF )
Output voltage at loading is referred Fig2. As standard example, however it depends on external components.
Shotky diodes
RB521-S30
15
Charge pump output
(V)
12
VBAT=5.5V
1µF
VBAT
1µF
OUTPUT VOLTAGE :
9
VBAT=3.6V
LED
C (Pin7)
6
3
VBAT=2.9V
0
0
20
40
60
80
(mA)
100
OUTPUT LOAD :
Fig.2 Charge pump loading characteristics
(Typical operating characteristics)
2) Fixed current driver
LED driver fixed current is determined by resistor value between LEDS pin (pin4) and GND.
At current control set up voltage1 (Current1, 2=High) resistor value between LEDS-GND is set as 2.7Ω.
205mV
÷
2.7Ω = 75.9mA
(2 expressions)
The above current is loaded to LED as fixied current.
LED
LED (5Pin)
+
−
LEDS (4Pin)
CURRENT1
CURRENT2
RSENSE
•
LED drive current fix example
LEDS pin voltage
(mV)
Current control setup voltage 1 (Current 1=High Current 2=High)
Current control setup voltage 2 (Current 1=Low Current 2=High)
Current control setup voltage 3 (Current 1=High Current 2=Low)
Current control setup voltage 4 (Current 1=Low Current 2=Low)
205.0
155.0
105.0
55.0
LED drive current (mA)
RSENSE=2.7Ω RSENSE=5.1Ω
75.9
57.4
38.9
20.4
40.2
30.4
20.6
10.8
The less RSENSE, the bigger fixed current for LED drive.
Resistors value should be determined with confirmation of charge pump loading characteristics (Fig.2) and LED's I-V characteristics.
4/7
BD6155FVM
Communication ICs
!
Design information
1. The maximum of power loss of this IC is controlled by the output transistor M1 in regulator driver.
Relations of the power supply voltage are signified in 2 expressions with this loss.
∆V
= V
OUT
−
(VF2
+
ILED
×
R1
+
VLED)
The loss in M1,
∆V ×
ILED = ILED
×
{2VBAT− (2VF1
+
VF2
+
ILED
×
R1
+
VLED)}
(2 expressions)
∆V
; The voltage between LED-LEDS
VF1 ; Shotky’s Di VF
VF2 ; LED’s VF
V
OUT
; Charge pump output voltage (Fig.2)
VLED ; The voltage across RSENSE (examples at 205mV calculation)
ILED ; Drive current.
ILED
VF1
VF1
V
OUT
V
BAT
VF2
LED
R1
LED
LEDS
M1
RSENS
0.2V
∆V
Room temperature power dissipation
(350mW)
Pd-V
BAT
300
Loss Pd : (mW)
200
I
O
=50mA
100
I
O
=80mA
VF1=0.5V
VF2=3.4V
R1=0Ω
0
2
3
4
5
6
Power supply voltage V
BAT
(V)
2) Power supply voltage
The thermal shutdown circuit turn on, and output electric current declines when chip temperature is about 125 degrees
due to low electric current driver.
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