Rainbow Electronics MAX8815A - Manual (Page 8)

MAX8815A
1A, 97% Efficiency, 30µA Quiescent Current
Step-Up Converter with True Shutdown
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Detailed Description
The MAX8815A current-mode step-up DC-DC switching
converter uses a fixed-frequency PWM architecture with
True Shutdown. In normal mode, the converter switches
when needed, consuming only 30µA of quiescent cur-
rent. In forced-PWM mode (FPWM), the converter
switches every cycle at a constant frequency, thus
enabling noise filtering. The MAX8815A is highly effi-
cient, with an internal switch and synchronous rectifier.
Shutdown reduces the quiescent current to less than
0.1µA. Low quiescent current and high efficiency make
this device ideal for powering portable equipment.
The MAX8815A step-up DC-DC switching converter typ-
ically generates a 3.3V to 5V output voltage from a 1.2V
to 5.5V battery input voltage. The converter operates in
bootstrapped mode with the output powering the device
once the output voltage is ≥ 3V. The current limit is set at
2.5A to deliver 1A at 5V from a 2.5V input, or 500mA at
5V using a 2-cell 1.8V input. Internal soft-start limits the
inrush current to less than 500mA under no-load condi-
tions during startup.
The MAX8815A switches at a 2MHz frequency, allow-
ing for tiny external components. Internal compensation
further reduces the external component count in cost
and space-sensitive applications. The MAX8815A is
optimized for use in DSC and other applications requir-
ing low quiescent current for maximum battery life.
Figures 1a and 1b show the typical application circuits.
ON SKIPB
POUT
BATT
LX
FB
OUTS
GND
ON
ON
3V
ON
ON
PGND
CONTROL
2MHz
OSCILLATOR
REFERENCE
EP
+
-
STARTUP
OSCILLATOR
MAX8815A
Functional Diagram