9
FN7415.2
February 22, 2006
Applications Information
The EL7640, EL7641, EL7642 provide a highly integrated
multiple output power solution for TFT-LCD applications.
The system consists of one high efficiency boost converter
and two low cost linear-regulator controllers (V
ON
and
V
OFF
) with multiple protection functions. The block diagram
of the whole part is shown in Figure 17. Table 1 lists the
recommended components.
The EL7640, EL7641, EL7642 integrate an N-channel
MOSFET in boost converter to minimize the external
component counts and cost. The V
ON
, V
OFF
linear-
regulators are independently regulated by using external
resistors. To achieve higher voltage than V
BOOST
, one or
multiple stage charge pumps may be used.
FIGURE 13. START-UP SEQUENCE FIGURE 14. OP AMP RAIL-TO-RAIL INPUT/OUTPUT
FIGURE 15. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
FIGURE 16. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
Typical Performance Curves (Continued)
INPUT
VOLTAGE
V
BOOST
V
ON
V
OFF
C
DEL
=220nF
TIME (20ms/DIV)
INPUT
OUTPUT
TIME (50µs/DIV)
JEDEC JESD51-3 AND SEMI G42-88
(SINGLE LAYER) TEST BOARD
0.8
0.7
0.5
0.3
0.2
0.1
0
0 255075100 150
AMBIENT TEMPERATURE (°C)
POWER DISSIPATION (W)
12585
0.6
0.4
JA
=125°C/W
QFN32
758mW
JEDEC JESD51-7 HIGH EFFECTIVE
THERMAL CONDUCTIVITY TEST BOARD -
QFN EXPOSED DIEPAD SOLDERED TO
PCB PER JESD51-5
3
2.5
2
1.5
1
0.5
0
0 255075100 150
AMBIENT TEMPERATURE (°C)
POWER DISSIPATION (W)
2.857W
JA
=35°C/W
QFN32
12585
TABLE 1. RECOMMENDED COMPONENTS
DESIGNATION DESCRIPTION
C
1
, C
2
, C
3
10µF, 16V X5R ceramic capacitor (1210)
TDK C3216X5R0J106K
D
1
1A 20V low leakage schottky rectifier
(CASE 457-04)
ON SEMI MBRM120ET3
D
11
, D
12
, D
21
200mA 30V schottky barrier diode (SOT-23)
Fairchild BAT54S
L
1
6.8µH 1.3A Inductor
TDK SLF6025T-6R8M1R3-PF
Q
11
200mA 40V PNP amplifier (SOT-23)
Fairchild MMBT3906
Q
21
200mA 40V NPN amplifier (SOT-23)
Fairchild MMBT3904
EL7640, EL7641, EL7642
