MAX8727(2004) 데이터 시트보기 (PDF) - Maxim Integrated
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MAX8727 Datasheet PDF : 13 Pages
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TFT-LCD Step-Up DC-DC Converter
Pin Description
PIN NAME
FUNCTION
1
COMP Compensation Pin for Error Amplifier. Connect a series RC from COMP to ground. See the Loop
Compensation section for component selection guidelines.
Feedback Pin. The FB regulation voltage is 1.24V nominal. Connect an external resistive voltage-divider
2
FB
between the step-up regulator’s output (VOUT) and GND, with the center tap connected to FB. Place the
divider close to the IC and minimize the trace area to reduce noise coupling. Set VOUT according to the
Output Voltage Selection section.
3
SHDN Shutdown Control Input. Drive SHDN low to turn off the MAX8727.
4
GND Ground. Connect pins 4 and 5 directly together.
5
GND Ground. Connect pins 4 and 5 directly together.
6
LX
Switch Pin. LX is the drain of the internal MOSFET. Connect the inductor/rectifier diode junction to LX and
minimize the trace area for lower EMI. Connect pins 6 and 7 directly together.
7
LX
Switch Pin. LX is the drain of the internal MOSFET. Connect the inductor/rectifier diode junction to LX and
minimize the trace area for lower EMI. Connect pins 6 and 7 directly together.
8
IN Supply Pin. Bypass IN with a minimum 1µF ceramic capacitor directly to GND.
9
FREQ
Frequency-Select Input. When FREQ is low, the oscillator frequency is set to 640kHz. When FREQ is high, the
frequency is 1.2MHz. This input has a 5µA pulldown current.
Soft-Start Control Pin. Connect a soft-start capacitor (CSS) to this pin. Leave open for no soft-start. The soft-
10
SS
start capacitor is charged with a constant current of 4.5µA. Full current limit is reached after t = 2.5 × 105 CSS.
The soft-start capacitor is discharged to ground when SHDN is low. When SHDN goes high, the soft-start
capacitor is charged to 0.4V, after which soft-start begins.
VIN
4.5V TO 5.5V
C1
10µF
6.3V
L1
3.6µH
D1
R3
6
7
10Ω
LX
LX
8
IN
C3
FB 2
1µF
MAX8727
9
FREQ
GND 5
3 SHDN
GND 4
10
SS
C6
33nF
COMP 1
R1
309kΩ
1%
C2
4.7µF
25V
R2
28.0kΩ
1%
R4
100kΩ
C5
39pF
C4
330pF
C7
4.7µF
25V
C8
4.7µF
25V
VOUT
15V/600mA
Figure 1 Typical Operating Circuit
6 _______________________________________________________________________________________
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