el7585il-t7 Intersil Corporation, el7585il-t7 Datasheet - Page 12

• Manufacturer Part Number: el7585il-t7
• Description: Tft-lcd Power Supply
• Manufacturer: Intersil Corporation

The base-emitter saturation voltage is: Vbe_max = 1.25V
(note this is normally a Vbe ~ 0.7V, however, for the Q5
transistor an internal Darlington arrangement is used to
increase it's current gain, giving a 'base-emitter' voltage of
2 x V
(Note that using a high current Darlington PNP transistor for
Q5 requires that V
voltage be required, then an ordinary high gain PNP
transistor should be selected for Q5 so as to allow a lower
collector-emitter saturation voltage).
For the EL7585, the minimum drive current is:
I_DRVL_min = 8mA
The minimum base-emitter resistor, R
calculated as:
R
1.25V/(8mA - 500mA/100) = 417Ω
This is the minimum value that can be used - so, we now
choose a convenient value greater than this minimum value;
say 500Ω. Larger values may be used to reduce quiescent
current, however, regulation may be adversely affected, by
supply noise if R
0.9V
PG_LDOP
BL
_min = V
BE
FIGURE 21. V
).
+
GMP
-
BE
+
-
_max/(I_DRVL_min - Ic/Hfe_min) =
BL
1: Np
IN
is made too high in value.
ON
CLAMP
LDO_ON
> V
ESD
36V
FUNCTIONAL BLOCK DIAGRAM
LOGIC
12
DRVP
FBP
+ 2V. Should a lower input
R
7kΩ
BP
BL
20kΩ
R
R
, can now be
V
P1
P2
BOOST
Q3
CP (TO 36V)
V
ON
0.1µF
(TO 35V)
0.1µF
C
ON
LX
EL7585
The V
of the row driver in the LCD panel. The DC/DC consists of an
external diode-capacitor charge pump powered from the
inductor (LX) of the boost converter, followed by a low
dropout linear regulator (LDO_ON). The LDO_ON regulator
uses an external PNP transistor as the pass element. The
onboard LDO controller is a wide band (>10MHz)
transconductance amplifier capable of 4mA drive current,
which is sufficient for up to 40mA or more output current
under the low dropout condition (forced beta of 10). Typical
V
+36V. A fault comparator is also included for monitoring the
output voltage. The under-voltage threshold is set at 25%
below the 1.2V reference.
The V
supply of the row driver in the LCD panel. The DC/DC
PG_LDON
ON
0.9V
PG_LDOL
0.4V
FIGURE 23. V
voltage supported by EL7585 ranges from +15V to
FIGURE 22. V
ON
OFF
GMN
+
-
power supply is used to power the positive supply
+
GML
power supply is used to power the negative
-
+
-
+
CLAMP
-
ESD
36V
1: Nn
LOGIC
1: N1
LDO_OFF
OFF
LDO_LOG
FUNCTIONAL BLOCK DIAGRAM
FUNCTIONAL BLOCK DIAGRAM
FBN
DRVN
R
3kΩ
BN
DRVL
FBL
500Ω
R
BL
20kΩ
R
R
N2
N1
V
V
20kΩ
IN
REF
R
R
(3V TO 6V)
Q2
L1
L2
OR V
Q5
0.1µF
(1.3V TO 3.6V)
PROT
CP (TO -26V)
V
V
OFF
LOGIC
March 9, 2006
(TO -20V)
0.1µF
C
LX
C
10µF
FN7345.2
OFF
LOG