AIC1652 Datasheet, PDF (4/6 Pages) Analog Intergrations Corporation – MICROPOWER INVERTING DC/DC CONVERTER

n ^{PIN DESCRIPTIONS}
PIN 1: VIN - 2.4V to 7V input supply voltage.
PIN 2:
VREF - 1.22V reference output. Bypass with
a 0.047µF capacitor to GND.
Sourcing capability is guaranteed to
be greater than 250µA.
PIN 3:
SHDN - Logic input to shutdown the chip.
>1.5V = normal operation,
GND = shutdown
In shutdown mode DLOW and DHI
pins are at high level.
PIN 4: FB
- Feedback signal input to sense
ground. Connecting a resistor R1 to
V_OUT and a resistor R2 to V_REF pin
yields the output voltage:
V_OUT = -(R1/R2 ) x V_REF
PIN 5: GND - Power ground.
AIC1652
MICROPOWER INVERTING DC/DC CONVERTER
SPEC NO: DS-1652-02 DEC 27, 00
PIN 6: DLOW - Driver sinking output. Connected to
DHI when using an external P-
channel MOSFET. When using an
external PNP bipolar transistor,
connect a resistor RB from this pin
to DHI. RB value depends on V_IN,
inductor and PNP bipolar transistor.
By adjusting the RB value, efficiency
can be optimized.
PIN 7: DHI
- Driver sourcing output. Connect to
gate of the external P-channel
MOSFET or base of the PNP bipolar
transistor.
PIN 8: CL
- Current-limit input. This pin clamps
the switch peak current to prevent
over-current damage to the external
switch.
n ^{APPLICATION INFORMATIONS}
Max. Output Power vs VIN
0.8
Typical Application Circuit
100µH
0.6
120 µH
150 µH
0.4
180 µH
220 µH
Inductor Value
0.2
02
4
6
8
VIN (V)
The typical application circuit generates an adjustable
negative voltage for contrast bias of LCD displays. Effi-
ciency and output power can be optimized by using ap-
propriate inductor and switch. The following formulas
provide a guideline for determining the optimal component
values:
L = (11.1 − 0.15 × VIN) ×
V IN
IOUT × VOUT
PNP : VCEO > VIN + VOUT
IOUT
IC,MAX ≥ 200 ×
VIN
VCE < 0. 4 V at I C = 200 × ^IOUT
V IN
and β = 10
RB ≅ 3 x L x (V_IN - 0.8)
where, units: V_IN & V_OUT in V, I_OUT in A, L in µH,
RB in Ω
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