ISL78010_14 Datasheet, PDF (13/19 Pages) Intersil Corporation – Automotive Grade TFT-LCD Power Supply

ISL78010
For the ISL78010, the minimum drive current is as shown in
Equation 10:
I_DRVL(min) = 8mA
(EQ. 10)
The minimum base-emitter resistor, R_BL, can now be
calculated as shown in Equation 11:
R_BL(min) = V_BE(max) ⁄ (I_DRVL(min) – I_C ⁄ h_FE(min)) =
1.25V ⁄ (8mA – 500mA ⁄ 100) = 417Ω
(EQ. 11)
This is the minimum value that can be used. Choose a
convenient value greater than this minimum value; for
example, 500Ω. Larger values may be used to reduce
quiescent current; however, regulation may be adversely
affected by supply noise if the value of R_BL is too high.
V_BOOST
LX
0.9V
PG_LDOP ₊
-
+
-
GMP
LDO_ON
0.1µF
36V
ESD
CLAMP
CP (TO 36V)
R_BP
7kΩ
DRVP
FBP
0.1µF
Q3
V_ON (TO 35V)
R_P1
R_P2
20kΩ
C_ON
1: Np
FIGURE 23. V_ON FUNCTIONAL BLOCK DIAGRAM
LX
0.1µF
PG_LDON _-
+
0.4V
LDO_OFF
V_REF
FBN
R_N2
20kΩ
1: Nn
-
+
GMN
36V
ESD
CLAMP
R_N1
DRVN
Q2
R_BN
3kΩ
CP (TO -26V)
0.1µF
V_OFF (TO -20V)
C_OFF
FIGURE 24. V_OFF FUNCTIONAL BLOCK DIAGRAM
0.9V
PG_LDOL ₊
-
LDO_LOG
V_IN OR V_PROT
(3V TO 6V)
R_BL
500Ω
DRVL
FBL
Q5 _VLOGIC
(1.3V TO 3.6V)
C_LOG
R_L1
10µF
-
+
GML
1: N1
R_L2
20kΩ
FIGURE 25. V_LOGIC FUNCTIONAL BLOCK DIAGRAM
The V_ON power supply is used to power the positive supply
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
on-board 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_ON voltage supported by the ISL78010 ranges from +15V
to +36V. A fault comparator is also included for monitoring
the output voltage. The undervoltage threshold is set at 25%
below the 1.2V reference.
The V_OFF power supply is used to power the negative
supply 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_OFF). The
LDO_OFF regulator uses an external NPN transistor as the
pass element. The on-board 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_OFF voltage supported by the ISL78010 ranges
from -5V to -20V. A fault comparator is also included for
monitoring the output voltage. The undervoltage threshold is
set at 200mV above the 0.2V reference level.
The V_LOGIC power supply is used to power the logic circuitry
within the LCD panel. The DC/DC may be powered directly
from the low voltage input, 3.3V or 5.0V, or it may be
powered through the fault protection switch. The
LDO_LOGIC regulator uses an external PNP transistor as
the pass element. The on-board LDO controller is a wide
band (>10MHz) transconductance amplifier capable of
16mA drive current, which is sufficient for up to 160mA or
13
FN6501.2
December 4, 2013