AAT3190
Positive/Negative Charge Pump for Voltage Bias
Functional Block Diagram
IN
DRVP
UVLO
EN
Control
DRVN
Reference
Oscillator
+
-
FBP
Over-
Temperature
Protection
Band
Gap
Ref.
REF
GND
-
+
FBN
Functional Description
Dual Charge Pump Regulators
The AAT3190 provides low-power regulated output
voltages from two individual charge pumps. Using
a single stage, the first charge pump inverts the
supply voltage (V
IN
) and provides a regulated neg-
ative output voltage. The second charge pump dou-
bles V
IN
and provides a regulated positive output
voltage. These outputs use external Schottky
diodes and capacitor multiplier stages (as many as
required) to regulate up to ±25V. A constant switch-
ing frequency of 1MHz minimizes the output ripple
and capacitor size.
Negative Charge Pump
During the first half-cycle, the P-channel MOSFET
turns on and the flying capacitor C7 charges to V
IN
minus a diode drop (Figure 1). During the second
half-cycle, the P-channel MOSFET turns off and
the N-channel MOSFET turns on, level shifting C7.
This connects C7 in parallel with the output reser-
voir capacitor C10. If the voltage across C10
minus a diode drop is less than the voltage across
C7, current flows from C7 to C10 until the diode
turns off.
8
3190.2005.03.1.0
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
