Rainbow Electronics MAX8712 - Manual (Page 10)

MAX8710/MAX8711/MAX8712
Low-Cost Linear-Regulator
LCD Panel Power Supplies
10 ______________________________________________________________________________________
PIN
NAME
MAX8710 MAX8711 MAX8712
FUNCTION
FBP 17 12 8
Positive Charge-Pump Feedback Input. Connect FBP to the center of a resistive
voltage-divider between the positive charge-pump regulator output and GND to
set the regulator output voltage. Place the divider within 5mm of FBP. FBP is
internally pulled to GND by a 10
Ω
resistor in shutdown.
SHDN 18 13 9
Active-Low Shutdown Control Input. Pull SHDN low to turn off all sections of the
device except REF. Pull SHDN high to enable the device. Cycle SHDN to reset the
device after a fault.
CTL 19 — —
High-Voltage Switch-Control Block Timing Control Input. See the Switch Control
section for details.
FBL 20 14 10
Linear-Regulator Feedback Input. Connect FBL to the center of a resistive
voltage-divider between the linear-regulator output and GND to set the linear-
regulator output voltage. Place the divider within 5mm of FBL.
MODE 21 — —
High-Voltage Switch-Control Block-Mode Selection Input and Timing-Adjustment
Input. See the Switch Control section for details. MODE is high impedance when it
is connected to REF. MODE is internally pulled to GND by a 1k
Ω resistor during
REF UVLO, when V DLP < 2.5V, or in shutdown.
DLP 22 15 11
Positive Charge-Pump Startup Delay and High-Voltage Switch Delay Input.
Connect a capacitor from DLP to GND to set the delay time. A 5µA current source
charges C
DLP . DLP is internally pulled to GND by a 10
Ω
resistor in shutdown.
FBN 23 16 12
Negative Charge-Pump Feedback Input. Connect FBN to the center of a resistive
voltage-divider between the negative output and REF to set the output voltage.
Place the divider within 5mm of FBN. FBN is internally pulled to GND through a
10
Ω resistor in shutdown.
SRC 24 — —
Switch Input. Source of the internal high-voltage P-channel MOSFET connected to
GON.
Pin Description (continued)
Typical Operating Circuit
Figures 1, 2, and 3 are the Typical Operating Circuits of
the MAX8710, MAX8711, and MAX8712 for generating
power rails in TFT LCD panels. The input voltage range
is from 10.8V to 13.2V. The AVDD output is 10V at
300mA, the V
GON output is 27V at 20mA, and the
V GOFF output is -5V at 50mA.
Detailed Description
The MAX8710/MAX8711/MAX8712 include a high-perfor-
mance linear regulator, a positive charge-pump regula-
tor, a negative charge-pump regulator, and built-in
power-up sequence control. The MAX8710 and
MAX8711 also include a high-current operational amplifi-
er. Additionally, the MAX8710 provides logic-controlled
high-voltage switches to control the positive charge-
pump output. The linear regulator directly steps down the
input voltage to generate the source-driver ICs’ supply
voltage. The two built-in charge-pump regulators are
used to generate the TFT gate-on and gate-off supplies.
The high-current operational amplifier is typically used to
drive the LCD backplane (VCOM) and features high out-
put current (150mA), fast slew rate (12V/µs), and wide
bandwidth (12MHz). Its rail-to-rail inputs and output maxi-
mize flexibility.
Linear Regulator
MAX8710/MAX8711/MAX8712 contain a linear regulator
that uses an internal PNP pass transistor to supply load
currents up to 300mA. Connect an external resistive volt-
age-divider between the regulator output and GND with
the midpoint connected to FBL to adjust the linear-regu-
lator output. An error amplifier compares the FBL voltage
with the 2.5V internal reference voltage and amplifies the
difference. If the feedback voltage is higher than the