Quad-PWM-controller IC includes low-dropout linear regulator
By Paul Rako, Technical Editor -- EDN, October 19, 2009
Exar Corp’s new 5A XRP7704 and 16A XRP7740 quad-PWM (pulse-width-modulation)-controller chips include gate-driver circuitry that drives external FETs. In addition to the four PWM voltage regulators, the devices include a low-dropout linear regulator, which you can use for auxiliary or standby power. The input-voltage range is 6.5 to 20V, and you can set the output voltages at 0.9 to 5V. The four PWM outputs have 12-bit resolution, and the units, which you can program through an I2C (inter-integrated-circuit) interface, have six general-purpose digital-I/O pins. They use a digital PID (proportional/integral/differential) algorithm that tailors control-loop response up to a 1.5-MHz switching frequency. Applications include POL (point-of-load) dc/dc-power conversion in high-volume and cost-sensitive consumer devices, such as set-top boxes, and industrial markets, such as servers and instrumentation. The units store their settings in OTP (one-time-programmable) memory, but your system processor can overwrite those settings using the I2C bus.
The Digital Power Studio software environment allows you to program and communicate with the chips as you develop your power system. The package lets you configure the power supply’s voltage settings, current thresholds, fault monitoring and response, soft start, shutdown, channel sequencing, phase-shift management, and loop response. You can also control the parts in real-time using the I2C port with your system microcontroller, FPGA, or ASIC. You can configure as many as eight PWM controllers by linking two parts together in a master-slave arrangement.
Both parts come in 40-pin QFN packages, comply with ROHS (reduction-of-hazardous-substances) directives, operate at −40 to +85°C, and are available for sampling. The XRP7704 sells for $4, and the XRP7740 sells $5.50 (1000).
