The LM2687 CMOS Negative Regulated Switched Capacitor
Voltage Inverter delivers a very low noise adjustable output
for an input voltage in the range of +2.7V to +5.5V. Four low
cost capacitors are used in this circuit to provide up to 10mA
of output current. The regulated output for the LM2687 is
adjustable between ?1.5V and ?5.2V. The LM2687 operates
at 100 kHz (typical) switching frequency to reduce output
resistance and voltage ripple. With an operating current of
only 500 μA (charge pump power efficiency greater than
90% with most loads) and 0.05 μA typical shutdown current,
the LM2687 provides ideal performance for cellular phone
power amplifier bias and other low current, low noise negative
voltage needs. The device comes in a small 8-pin MSOP
or LLP package.