LV52207NXA Application Notes
Rev-A
Page No. Update Date
1
2014/7/4
2
2014/6/3
3
2014/6/3
5
2014/6/3
6
2014/6/3
10
2014/6/3
11
2014/6/3
Contents
Overall composition
Explanation of the terminal
LED Currents setting and Select of control mode
Start/ShutDown sequences
LED OPEN/SHORT
Board layout
External Part Selection
2014/7/4
Typical Applications
. LED Display Backlight Control
VIN
(2.7V½5.5V）
1uF
4.7uH
10Ω
1uF
VCC
1uF
Enable/Disable
1-wire
PWM DIMMING
SW
EN
PWM
FCAP
330nF
GND
LEDO1
LEDO2
RT
63.4KΩ
< Overall composition >
LV52207NXA is a Boost type DC-DC convertor for White LED drive.
It integrated a MOSFET which can tolerate 40V.
The maximum LED current is set by resistance connected to RT terminal.
Case of 63.4Kohm, it is 20mA.
We can set 256 steps of current values by using 1-wire control. (Digital mode)
We can adjust dimming for LED currents by PWM signal. (PWM mode)
Change of LED current do not synchronize the PWM signal.
It is converted to DC current by LPF of FCAP PIN.
The switching frequency of LV52207NXA is 600kHz to improve efficiency
(The switching frequency of LV52207NXA is 1200kHz)
VBAT
L1
C1
R1
1uF
VCC
C4
1uF
UVLO
TSD
vref
OVP
OCP
D1
4.7uH
10Ω
SW
C2
1uF
GND
0.6MHz PWM
Controler
SWIRE
EN
PWM
PWM
dimming
1-wire/EN
CONTROL
LEDO1
LEDO2
FCAP
C3
330nF
D/A
IREF
RT
R2
63.4kΩ
Fig.1 Block Diagram
1
< Explanation of the terminal >
PIN
No.
A1
PIN
Sign
RT
Equivalent circuit
Explanations
Resistance connect PIN for maximum
LED current setting ;
Resistance to set the maximum LED
current is connected to this terminal
between GND.
Case of 63.4Kohm, the maximum LED
current is set 20mA to LEDO1 and
LEDO2.
A2
A3
LEDO2
LEDO1
Sink Pin of the LED current ;
This PIN connect to the cathodal of the
LED and pulls a set current.
The voltage is used for the feedback
control of DC-DC converter.
B1
PWM
Input PIN of PWM control signal ;
This PIN is used for dimming of the LED.
B2
FCAP
A
4
,
A
5
Filter PIN for input PWM signals ;
A capacitor to convert PWM signal into
DC is connected to this PIN.
B3
C1
GND
EN
GND PIN
Input PIN of EN and 1-wire control signal
;
This PIN is used for enabling and
dimming ( 1-wire control ) of the LED.
A
6
C2
C3
VIN
SW
Power supply PIN (2.7V-5.5V)
Switching PIN ;
SW is output PIN of DC-DC convertor.
It is used for overvoltage detection at the
time of the LED opening.
2
< LED Current setting and Select of control mode >
The LED current is set in the IC inside.
The maximum LED current is 20mA, when you select 63.4Kohm to RT resistor.
LED Current Setting (max sink current)
LED_full current is set by an external resistor connected between the RT pin and ground.
I(LED_full)= 2113 x (V(RT)/R(RT_res))
V(RT) : RT_pin DC Voltage typ=0.6V
R(RT_res) : RT_pin resistor
RT_res=63.4kohm：I(LED_full)=20mA
LED Current setting
Address=00
RT resistor = 63.4Kohm
LED current = I (maximum LED current) x code / 255 = LEDO1current = LEDO2current.
Table.1 Conversion list of LEDI Setting v.s. LED Current
code
0
1
2
3
4
5
6
7
8
9
10
.
.
.
246
247
248
249
250
251
252
253
254
255
D8
0
0
0
0
0
0
0
0
0
0
0
D7
0
0
0
0
0
0
0
0
0
0
0
D6
0
0
0
0
0
0
0
0
0
0
0
D5
0
0
0
0
0
0
0
0
0
0
0
.
.
.
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
1
1
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
D4
0
0
0
0
0
0
0
0
1
1
1
D3
0
0
0
0
1
1
1
1
0
0
0
D2
0
0
1
1
0
0
1
1
0
0
1
D1
0
1
0
1
0
1
0
1
0
1
0
LED Current (mA)
0 Unavailable
0.22
0.3
0.38
0.47
0.55
0.63
0.7
0.78
0.86
0.94
.
.
.
19.3
19.38
19.46
19.54
19.61
19.69
19.77
19.84
19.93
20
* Default
Fig.2 shows the control curve by the digital mode.
Fig.3 shows the control curve by the PWM mode.
By the PWM mode, the LED current is decided
with input signal DUTY.
Fig.2 Digital Mode
Fig.3 PWM Mode
3
Fig.7 RT resistance value VS LED CURRENT
Fig.8 CABC DIMMING
PWM DIMMING + 1-wire DIMMING
PAIR=(Imax-Iaverage)/Iaverage
Iaverage=(LEDO1current+LEDO2current)/2
Fig.9 PWM frequency VS LED CURRENT
Fig.10 Output Current Matching
4
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