MAX850 データシートの表示（PDF） - Maxim Integrated
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MAX850 Datasheet PDF : 8 Pages
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Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
______________________________________________________________Pin Description
MAX850
1
2
3
4
–
–
PIN
MAX851 MAX852
1
1
2
2
3
3
–
–
4
–
–
4
MAX853
1
2
3
4
–
–
NAME
C1+
C1-
NEGOUT
SHDN
SHDN
OSC
FUNCTION
Positive terminal for C1
Negative terminal for C1
Negative Output Voltage (unregulated), VNEGOUT = VIN + 0.2V
Active-low TTL logic level Shutdown Input
Active-high TTL logic level Shutdown Input
External Clock Input
Dual-Mode Feedback Input. When FB is grounded, the output is preset to
5
5
5
–
FB
-4.1V. To select other output voltages, connect FB to an external resistor
divider. See Figure 2b.
–
–
–
5
CONT
Control Voltage Input. To set VOUT, connect a resistor divider between
OUT and a positive control voltage between 0V and 10V. See Figure 2c.
6
6
6
6
OUT Output Voltage
7
7
7
7
GND Ground
8
8
8
8
IN
Positive Power-Supply Input (4.5V to 10V)
_______________Detailed Description
The MAX850–MAX853 are low-noise, inverting, regulat-
ed charge-pump power supplies designed for biasing
GaAsFET devices, such as power-amplifier modules in
cellular handsets.
The applied input voltage (VIN) is first inverted to a
negative voltage at NEGOUT by a capacitive charge
pump. This voltage is then regulated by an internal lin-
ear regulator, and appears at OUT (Figure 1). The mini-
mum (most negative) output voltage (VOUT) achievable
is the inverted positive voltage, plus the 1.0V required
by the post-regulator. The ripple noise induced by the
charge-pump inverter is reduced by the linear regulator
to 2mVp-p at VOUT for the MAX850–MAX852. In addi-
tion, the excellent AC rejection of the linear regulator
attenuates noise on the incoming supply. Up to 5mA is
available at OUT.
C1+
C1-
NEGOUT
CHARGE
PUMP
N
IN
MAX850
MAX851
MAX852
OUT
SHDN (MAX850)
SHDN (MAX851)
OSC (MAX852)
-1.28V
REF
FB
CONNECT TO
GND TO SET
VOUT = -4.1V
C1+
C1-
NEGOUT
SHDN
CHARGE
PUMP
N
IN
MAX853
OUT
CONT
CONTROL
VOLTAGE
GND
GND
Figure 1a. MAX850–MAX852 Block Diagram
Figure 1b. MAX853 Block Diagram
6 ______________________________________________________________________________________
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