AIC1620 データシートの表示（PDF） - Analog Intergrations

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AIC1620

High Efficiency Synchronous Step-Up DC/DC Converter

Analog Intergrations 

AIC1620/AIC1621/AIC1622

AIC1622

PIN 1: FB- Connect to OUT for +3.3V output.

Use a resistor network to set the

output voltage from +1.8V to +4.0V.

PIN 2: LBI- Low-Battery comparator input. Inter-

nally set to trip at +1.23V.

PIN 3: LBO- Open-drain low battery comparator

output. Output is low when VLBI is

<1.23V. LBO is high impedance

during shutdown.

PIN 4: CLSEL- Current-limit selects input. CLSEL=

OUT sets the current limit to 0.8A.

CLSEL=GND sets the current limit

to 0.45A.

PIN 5: REF- 1.23V reference voltage. Bypass

with a 0.1µF capacitor.

PIN 6: SHDN- Shutdown input. High=operating,

low=shutdown.

PIN 7: BATT- Battery input and damping switch

connection. If damping switch is

unused, leave BATT unconnected.

PIN 8: GND- Ground.

PIN 9: LX- N-channel and P-channel power

MOSFET drain.

PIN 10: OUT- Power output. OUT provides

bootstrap power to the IC.

n APPLICATION INFORMATION

Overview

The AIC1620/AIC1621/AIC1622 series are high effi-

ciency, step-up DC-DC converters, designed to fea-

ture a built-in synchronous rectifier, which reduces

size and cost by eliminating the need for an external

Schottky diode. The start-up voltage is as low as

0.9V and operate with an input voltage down to 0.7V.

Quiescent supply current is only 20µA. In addition,

the AIC1622 feature a circuit that eliminates inductor

ring to reduce noise. The internal P-MOSFET on-

resistance is typically 0.3Ω to improve overall effi-

ciency by minimizing AC losses. The current limit of

the AIC1620 and AIC1621 are 0.8A and 0.45A re-

spectively. The AIC1622 offers a selectable current

limit(0.45A or 0.8A). The lower current limit allows the

use of a physically smaller inductor in space-

sensitive applications.

PFM Control Scheme

The key feature of the AIC1620 series is a unique

minimum-off-time, current-limited, pulse-frequency-

modulation (PFM) control scheme (see BLOCK

DIAGRAM) with the ultra-low quiescent current . A

constant-peak-current limit in the switching allows the

inductor current to vary between this peak limit and

some lesser value. The peak current of the internal N-

MOSFET power switch can be fixed at 0.8A, 0.45A or

is selectable. Besides, the ripple voltage dose not

exceed the product of the peak current limit and the

filter capacitor equivalent series resistance (ESR).

The switch frequency depends on the loading condi-

tion and input voltage, and can range up to 500KHz.

The switching frequency is governed by a pair of one-

shots that set a minimum off-time (1µS) and a maxi-

mum on-time (4µS).

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