The MAX1798/MAX1798A/MAX1799/MAX1799A system power supplies are designed specifically for CDMA cellular/PCS handsets. Each device contains five low-dropout linear regulators (LDOs), a 140ms (min) reset timer, a serial interface, push-on/push-off control logic, and two general-purpose open-drain outputs. Only the serial interface is different between the MAX1798/MAX1798A/MAX1799/MAX1799A: the MAX1798/MAX1798A feature an SPI-compatible serial interface, and the MAX1799/MAX1799A feature an I2C-compatible interface. The "A" parts have a -13% reset threshold, the non-A parts have a 9.5% threshold. The "A" parts have a 175 delay on a reset-triggered shutdown, the non-A shutdown instantly. Each linear regulator features extremely low dropout voltage, specified at two-thirds of the maximum output current. LDO1 is rated for 300mA, while LDOs 2–5 are each rated for 150mA. All LDOs are optimized for low noise and isolation. Each LDO can be individually enabled and disabled through the serial port, as well as individually programmed to any of 32 voltages from 1.8V to 3.3V. The MAX1798/MAX1798A/MAX1799/MAX1799As' wide 2.5V to 5.5V input voltage range makes them compatible with a wide range of input supplies, including a single Li+ cell battery. Both devices are available in thermally enhanced 20-pin TSSOP and TQFN exposed pad (EP) packages. Evaluation kits (MAX1798EVKIT and MAX1799EVKIT) are available to facilitate designs.
Feature
- One 300mA Low-Noise LDO
- Four 150mA Low-Noise LDOs
- 45μVRMS Noise from 10Hz to 100kHz
- > 60dB Crosstalk Isolation Below 10kHz
- > 60dB PSRR Below 10kHz
- 125mV (max) Dropout (OUT1 at 200mA)
- 100mV (max) Dropout (OUT2–5 at 100mA)
- Programmable Output Voltages
- 140ms (min) Reset Timer
- SPI- or I2C-Compatible Serial Interface
- Push-On/Push-Off Control Logic
- Two 150mA General-Purpose Open-Drain Outputs
- Overcurrent and Thermal Protection (all LDOs)
- 1μA Shutdown Current
- 20-Pin Thermally-Enhanced TSSOP or TQFN Packages
Applications
- 2- or 3-Cell NiMH, NiCd, or Alkaline Systems
- CDMA Cellular/PCS Handsets
- Handy Terminals
- Palmtop Computers
- PDAs
- Single-Cell Li+ Systems
