AAT3190
Positive/Negative Charge Pump for Voltage Bias
IN
1/2 A4
C7
OSC
DRVN
CTL
BAT54SDW
VON = -(R1/R2) x VREF
VON
R1
FBN
R2
C10
VREF
1.2V
C2
AAT3190
GND
Figure 1: Negative Charge Pump Block Diagram.
MOSFET turns on, level shifting C4 by the input
Positive Charge Pump
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 + VIN), charge is transferred from C4
to C5 until the diode turns off.
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
IN
VIN
1/2 A3
C4
OSC
CTL
DRVP
BAT54SDW
R3
VOP
FBP
VOP = (1+R3/R4) x VREF
VREF
1.2V
R4
C5
AAT3190
GND
Figure 2: Positive Charge Pump Block Diagram.
3190.2006.01.1.2
9
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
