AIC1641 Datasheet, PDF (8/12 Pages) List of Unclassifed Manufacturers – LOW VOLTAGE STEP-UP DC/DC CONVERTER

APPLICATION INFORMATION
GENERAL DESCRIPTION
AIC1641 PFM (pluse frequency modulation) control-
ler ICs combine a switch mode regulator, push pull
driver, precision voltage reference, and voltage de-
tector in a single monolithic device. They offer both
extreme low quescient current, high efficiency, and
very low gate threshold voltage to ensure start-up
with low battery voltage ( 0.8V typ.). Designed to
maximize battery life in protable products, and mini-
mize switching losses by only switching as needed
service the load.
PFM controllers transfer a discreate amount of ener-
gy per cycle and regulate the output voltage by
modulating switching frequency with the constant
turn-on time. Switching frequency depends on load,
input voltage, and inductor value, and it can range up
to 100KHz.
When the output voltage drops, the error comparator
enable 100kHz oscillator that turns on the MOSFET
around 7.5µs and 2.5µs off time. Turning on the
MOSFET allows inductor current to ramp up, storing
energy in a magnetic field. When MOSFET turns off
that forces inductor current through diode to the out-
put capacitor and load. As the stored energy is de-
pleted, the current ramp down until the diode turns
off. At this point, inductor may ring due to residual
energy and stray capacitance. The output capacitor
stores charge when current flowing through the di-
ode is high, and release it when current is low,
thereby maintaining a steady voltage across the load.
As the load increases, the output capacitor dis-
charges faster and the error comparator initiates cy-
cles sooner, increasing the switching frequency. The
maximum duty cycle ensure adequate time for ener-
gy tranfer to output during the second half each cycle.
Depending on circuit, PFM controller can operate in
either discontinuous mode or continuous conduction
AIC1641
LOW VOLTAGE STEP-UP DC/DC CONVERTER
SPEC NO: DS-1641-00 05/04/00
mode. Continuous conduction mode means that the
inductor current does not ramp to zero during each
cycle.
VIN
I_IN
SW
EXT
Isw
I_D
I_OUT
+
V_OUT
Ico
V_EXT
I_IN
I_PK
I_SW
Charge Co.
I_D
I_OUT
T_DIS Discharge Co.
V_SW
t
Discontinuous Conduction Mode
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