The LTC1550/LTC1551 are switched capacitor charge pump voltage inverters which include internal linear post-regulators to minimize output ripple. Output voltages are fixed at –4.1V, with ripple voltages typically below 1mVP-P. The LTC1550LCMS8-2 is also available in an adjustable output voltage version. The LTC1550/LTC1551 are ideal for use as bias voltage generators for GaAs transmitter FETs in portable RF and cellular telephone applications.
The LTC1550/LTC1551 operate from single 4.5V to 6.5V supplies and draw typical quiescent currents of 4.25mA with a 5V supply. Each device includes a TTL compatible Shutdown pin which drops supply current to 0.2µA typically. The LTC1550LCMS8-2 Shutdown pin is active low (SHDN), while the LTC1551 Shutdown pin is active high (SHDN). Only four external components are required: an input bypass capacitor, two 0.1µF charge pump capacitors and a filter capacitor at the linear regulator output. The adjustable LTC1550LCMS8-2 requires two additional resistors to set the output voltage. The LTC1550/LTC1551 will supply up to 10mA output current with a 5V supply, while maintaining guaranteed output regulation of ±5%.
The fixed voltage LTC1550/LTC1551 are available in S0-8 plastic packages. The adjustable LTC1550LCMS8-2 is available in a 16-pin SSOP.
Feature
- Regulated Negative Voltage from a Single Positive Supply
- Low Output Ripple: Less Than 1mVP-P Typ
- High Charge Pump Frequency: 900kHz Typ
- Small Charge Pump Capacitors: 0.1µF
- Requires Only Four External Capacitors
- Fixed −4.1V or Adjustable Output
- Shutdown Mode Drops Supply Current to < 1µA
- High Output Current: Up to 10mA, VCC = 5V
- Output Regulation: 5%
- Available in SO-8 and 16-Lead SSOP
Applications
- GaAs FET Bias Generators
- Negative Supply Generators
- Battery-Powered Systems
- Single Supply Applications
