PD70101 and PD70201

Introduction

The PD70101 and PD70201 devices are integrated Powered Device (PD) interface and PWM controllers for a DC-

DC converter used in IEEE

802.3af or IEEE 802.3at Type 1 applications, while the PD70201 device can also be used in IEEE 802.3at Type 2

applications.

A single PD70201 device can be used in 4-pair applications that consume up to 47.7 W.

These devices have a number of features designed to improve efficiency and reliability:

• Detection and Classification: The front-end interface includes detection and classification circuitry. The

detection signature resistor is disconnected upon completion of the detection phase. The system then begins

the classification phase. Classification can be configured for Classes 0 to 4 via an external resistor. The

PD70201 includes a two-events classification identification circuit, which generates a flag to inform the PD

application whether the Power Source Equipment (PSE) is Type 1 or Type 2.

• Capacitor: A current-limited internal MOSFET switch charges the input capacitor of the DC-DC converter. This

capacitor is discharged in a timely manner when the input power is removed.

• Gate drivers: The PWM DC-DC controller has two built-in gate drivers designed to swing between VCC and

GND. These two out-of-phase driver stages can be configured for synchronous rectification or active clamp.

• Peak current mode control: The DC-DC converter employs peak current mode control for better line and load

step response. The switching frequency can be set from 100 kHz to 500 kHz, enabling a size and efficiency

trade off.

• Maximum duty cycle is limited to 50% to reduce the power MOSFET switch voltage to two times the input

voltage; a 150V rated MOSFET can be used for the primary side switch. The secondary synchronous MOSFET

voltage rating depends on the output voltage and can be higher or lower than the primary side MOSFET switch.

• Soft-Start circuit: The devices include a soft-start circuit to control the output voltage rise time (user settable) at

start-up, and to limit the inrush current. An integrated startup bias circuit powers the DC-DC controller, until the

device starts up by the voltage generated by the bootstrap circuit.

• Low Voltage Protection Warning and Monitoring: Dual Under Voltage Lock Out (UVLO), which monitors both

the PoE Port Input Voltage and VCC, ensures reliable operation during any system disturbances. The PoE port

UVLO has a programmable threshold and hysteresis to enable tailoring to the desired turn-on and turn-off

voltage.

An internal current sense amplifier with a Kelvin connection allows the use of an extremely low resistor to measure

the current sense threshold voltage (200 mV) which optimizes efficiency.

Low Power Mode operation is provided to improve efficiency under light loads such as when the PD is in standby.

The user can define at what power level the unit enters low power mode by means of a single resistor value.

Datasheet

DS00003738A-page 1