Electronic Design

Integrated LDO Regulator Suits High-End Audio Portables

From an input supply of 3 to 5.5 V, the CM3702 integrated charge pump and linear low-dropout (LDO) regulator delivers 5 V to the analog input of a system's audio codec. The device, targeting high-quality audio applications, integrates a charge pump that boosts the voltage before feeding it to an internal LDO linear regulator. Also, the charge pump can be used with an external regulator.

The CM3702 maintains a nominal 0.8-V differential between the input and the output of the LDO regulator, leading to a power-supply ripple rejection (PSRR) of 42 dB across the audio band. It provides up to 200 mA of continuous output current at a nominal 5-V output. Typical operating current is 180 µA.

Dual Enable pins permit separate control of charge pump and LDO circuits for faster startup from sleep states. Overload current limiting and over-temperature thermal shutdown are provided.

The charge pump works with two external stable capacitors. It operates at 250 kHz, well outside the audible frequency band. Separate ground pins for the charge pump and the rest of the circuitry eliminate ground-noise feed-through from the charge pump to the regulated output. A bandgap reference bypass pin further minimizes noise.

The CM3702 is sampling along with evaluation boards. Housed in a 10-pin lead-free MSOP package, the LDO costs $0.57 each in 10,000-unit lots. Volume production is scheduled for this quarter.

California Micro Devices
(800) 325-4966

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