Charge pump IC for unipolar-to-bipolar or voltage doubling
The MAX1697UEUT+T is a charge pump voltage converter from Analog Devices that generates either a negative output equal to -Vin or a doubled positive output of 2Vin from a single positive supply, using only two external capacitors — no inductor required. Rated for 60 mA output current, it suits low-power bipolar rails for op-amp supplies, LCD bias, or sensor front-ends where a small PCB footprint matters more than efficiency at higher currents.
Input range and switching behaviour
The switching frequency free-runs between 120 kHz and 400 kHz depending on load and input voltage — no external clock or sync needed. The output is unregulated (open-loop charge pump), so the output voltage tracks the input: -Vin or 2Vin minus diode and switch drops under load. For a 5 V input at 60 mA, expect roughly -4.3 V or +9.3 V unloaded — the drop increases with load current.
SOT-23-6 package and board integration
Housed in a 6-lead SOT-23 (SOT-6 supplier package), the MAX1697UEUT+T occupies roughly 3 mm × 3 mm on the board. No synchronous rectification is used, so efficiency peaks around 80-85% at moderate loads — adequate for auxiliary rails where cost and size are the primary drivers.