LTC1144CN8 8-Lead PDIP Switched Capacitor Voltage Converter 2V to 18V Integrated Circuit Chip

The LTC1144CN8 is a monolithic CMOS switched capacitor voltage converter that turns a positive input into a complementary negative output. It accepts 2 V to 18 V and produces -2 V to -18 V, so a single part generates the negative rail for op-amps, data converters and RS-232 drivers in a mixed supply system.

Only two noncritical external capacitors are needed, one for the charge pump and one for the charge reservoir, so the whole converter fits in the space of a few passive parts. No inductor, diode or transformer is required, and the output is not ground referenced, which simplifies the layout.

An internal oscillator runs at 10 kHz when unloaded and can be slowed with an external capacitor or overdriven by an external clock for synchronisation. Tying the boost pin to V+ raises the frequency above the audio band so the converter does not whistle in audio equipment.

The shutdown pin drops the supply current to 8 microamps when the negative rail is not needed, which extends battery life in portable instruments. An internal divide-by-two, level shifter and four power MOSFETs are all included, and a logic circuit prevents the N-channel switch substrate from turning on during start-up.

The LTC1144CN8 is the commercial grade part in the 8-Lead Plastic DIP package, specified from 0 to 70 degrees C. It is RoHS compliant and lead free, every order ships with full traceability, and samples and volume pricing are available on request.

• Positive to negative voltage conversion
• Wide 2 V to 18 V input range
• Output from -2 V to -18 V
• Only two external capacitors needed
• No inductor or transformer
• 10 kHz internal oscillator
• Oscillator can be slowed or overdriven
• Boost pin moves noise above the audio band
• Shutdown pin reduces current to 8 microamps
• Internal level shifter and MOSFETs
• Compact eight pin package
• 8-Lead Plastic DIP package
• RoHS compliant, lead free

• Negative op-amp supplies
• Data converter bipolar supplies
• RS-232 driver supplies
• Portable instruments
• Battery powered systems
• Analog front ends

Typical use is a 5 V or 12 V rail converted to a matching negative rail for a bipolar op-amp or ADC front end.

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