参数资料
型号: MAX8795A+
厂商: MAXIM INTEGRATED PRODUCTS INC
元件分类: 稳压器
英文描述: 1.6 A SWITCHING REGULATOR, 1400 kHz SWITCHING FREQ-MAX, QCC32
封装: 5 X 5 MM, 0.80 MM HEIGHT, LEAD FREE, MO-220WHHD-2, TQFN-32
文件页数: 4/24页
文件大小: 387K
代理商: MAX8795A+
MAX8795A
TFT-LCD DC-DC Converter with
Operational Amplifiers
1
12
2
_
__
_
SUPPLIER
PHONE
FAX
WEBSITE
Fairchild
408-822-2000
408-822-2102
www.fairchildsemi.com
Sumida
847-545-6700
847-545-6720
www.sumida.com
TDK
847-803-6100
847-390-4405
www.component.tdk.com
Toshiba
949-455-2000
949-859-3963
www.toshiba.com/taec
Table 2. Component Suppliers
Detailed Description
The MAX8795A contains a high-performance step-up
switching regulator, two low-cost linear-regulator con-
trollers, multiple high-current operational amplifiers,
and startup timing and level-shifting functionality useful
for active-matrix TFT LCDs. Figure 2 shows the
MAX8795A functional diagram.
Main Step-Up Regulator
The main step-up regulator employs a current-mode,
fixed-frequency PWM architecture to maximize loop
bandwidth and provide fast transient response to
pulsed loads typical of TFT-LCD panel source drivers.
The 1.2MHz switching frequency allows the use of low-
profile inductors and ceramic capacitors to minimize
the thickness of LCD panel designs. The integrated
high-efficiency MOSFET and the IC’s built-in digital
soft-start functions reduce the number of external com-
ponents required while controlling inrush currents. The
output voltage can be set from VIN to 18V with an exter-
nal resistive voltage-divider.
The regulator controls the output voltage and the power
delivered to the output by modulating the duty cycle (D)
of the internal power MOSFET in each switching cycle.
The duty cycle of the MOSFET is approximated by:
Figure 3 shows the functional diagram of the step-up
regulator. An error amplifier compares the signal at FB
to 1.233V and changes the COMP output. The voltage
at COMP sets the peak inductor current. As the load
varies, the error amplifier sources or sinks current to the
COMP output accordingly to produce the inductor peak
current necessary to service the load. To maintain sta-
bility at high duty cycles, a slope-compensation signal
is summed with the current-sense signal.
On the rising edge of the internal clock, the controller sets
a flip-flop, turning on the n-channel MOSFET and applying
the input voltage across the inductor. The current through
the inductor ramps up linearly, storing energy in its
magnetic field. Once the sum of the current-feedback
signal and the slope compensation exceeds the COMP
D
VV
V
MAIN
IN
MAIN
STEP-UP
CONTROLLER
GATE-ON
CONTROLLER
SWITCH
CONTROL
GATE-OFF
CONTROLLER
REF
VCN
VCP
VMAIN
LX
FB
PGND
AGND
DRVP
FBP
VCP
VGON
VCN
VGOFF
DEL
CTL
DRVN
FBN
NEG4
REF
POS4
NEG5
POS5
OUT4
OUT5
BGND
NEG2
POS2
OP3
POS3
OUT2
OUT3
POS1
OUT1
NEG1
SUP
COM
DRN
SRC
COMP
IN
VIN
MAX8795A
OP2
OP1
OP5
OP4
EP
Figure 2. MAX8795A Functional Diagram
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