LT1942 LINER [Linear Technology], LT1942 Datasheet - Page 14

• Manufacturer Part Number: LT1942
• Description: Quad DCDC Converter for Triple Outputs TFT Supply Plus LED Driver
• Manufacturer: LINER [Linear Technology]

LT1942
TYPICAL APPLICATIO S
14
10V/DIV
10V/DIV
5V/DIV
1V/DIV
V
V
AVDD
SHDN
V
V
OFF
ON
3V TO 4.2V
–10V
2mA
V
2mA
V
10V
V
OFF
LED CONTROL VOLTAGE
ON
0.22µF
IN
16V
LED CONTROL
TFT Power Supply Sequencing
C2
SHUTDOWN
>2.5V
0.25V
<0.1V
Figure 4. TFT Bias (5V, 10V, –10V) and White LED Backlight Supply from Single Li-Ion Cell
665k
10k
R4
R3
V
IN
L5 47µH
L2 47µH
2ms/DIV
0.22µF
C5
22µF
16V
LED CURRENT
C3
DISABLED
C5 0.1µF 16V
2.5mA
20mA
U
C6
R5
698k
R6
100k
90
85
80
75
70
65
60
CTRL4
FB3
PGND23
V
NFB2
D2
SW2
SHDN
D3
OUT3
1942 F04c
5
AV
V
V
OFF
ON
DD
SGND/
AGND
10
SW3
LOAD = 2mA
LOAD = 2mA
LOAD = 40mA
V
L3 22µH
IN
TOTAL LED CURRENT (mA)
15
= 3.6V
LT1942
SS1
Efficiency
0.1µF
V
20
C7
0.1µF
CC
C8
22µH
V
SS4
25
IN
L1
AC-COUPLED
PGND14
= 4.2V
V
PGOOD
IN
20mV/DIV
50mA/DIV
SW1
LED1
LED2
SW4
CT
= 3V
30
FB1
FB4
D4
V
AVDD
C9
0.1µF
D1
I
LI
35
L4 33µH
AV
1942 F04b
DD
R2
100k
R1
301k
40
R7
4.99Ω
Transient Response, I
V
IN
4.7µF
6.3V
4.7pF
C1
30mA→40mA→30mA
C1 TO C9: X5R OR X7R
D1: CMDSH-3 CENTRAL SEMICONDUCTOR
L1: 22µH MURATA LQH32CN220K53
L2, L5: 47µH TAIYO YUDEN LB2012B470
L3: 22µH TAIYO YUDEN LB2012B220
L4: 33µH SUMIDA CDPH4D19-330MC
M1: Si2301BDS SILICONIX
100µs/DIV
R8
1M
PMOS
C4
4.7µF
25V X5R
M1
LOAD
AV
5V
40mA
DD
Stepped from
20mA
1942 F04a
1942 F04d
20mA
1942fa