AAT3190
Positive/Negative Charge Pump for Voltage Bias
IN
OSC
CTL
DRVN
C7
1/2 A4
BAT54SDW
FBN
R1
V
ON
= -(R1/R2) x V
REF
V
ON
R2
V
REF
1.2V
C10
C2
AAT3190
GND
Figure 1: Negative Charge Pump Block Diagram.
Positive Charge Pump
During the first half-cycle, the N-channel MOSFET
turns on and charges the flying capacitor C4
(Figure 2). During the second half-cycle, the N-
channel MOSFET turns off and the P-channel
MOSFET turns on, level shifting C4 by the input
voltage. This connects C4 in parallel with the reser-
voir capacitor C5. If the voltage across C5 plus a
diode drop is less than the level shifted flying
capacitor (C4 + V
IN
), charge is transferred from C4
to C5 until the diode turns off.
IN
V
IN
OSC
C4
CTL
DRVP
1/2 A3
BAT54SDW
FBP
R3
V
OP
V
OP
= (1+R3/R4) x V
REF
V
REF
1.2V
R4
C5
AAT3190
GND
Figure 2: Positive Charge Pump Block Diagram.
3190.2006.01.1.2
9
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
