Demoboard EVB25FX

Power Over Ethernet 802.3af/at PD Controller

Topology: Buck
Input Voltage (min.): 32.00 V
Input Voltage (max.): 57.00 V
Switching Frequency (min.): 100.00 kHz
Switching Frequency (max.): 500.00 kHz
Output 1: 12.00 V / 4.000 A

Original publication on 2011-09-25, revision 1.8


The PD70101 and PD70201 are integrated Powered Device Interface and PWM controllers for a DC-DC converter used in IEEE802.3af and IEEE802.3at applications. The PD70101 can be used for IEEE802.3af or IEEE802.3at Type 1 applications, while the PD70201 can also be used in IEEE802.3at Type 2 applications.A single PD70201 can be used in 4-pair applications which consumes up to 47.7W.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 2 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 100kHz to 500kHz, 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.


  • IEEE802.3af and IEEE802.3at Compliant
  • Support for 4-pair Applications of up to 47.7W With a Single IC
  • Two-events Classification Identification With a Level Signal Indicating Type 1 or Type 2 PSE
  • Less Than 10 μA (typical) Offset Current During Detection
  • Signature Resistor is Disconnected upon Detection
  • Programmable Classification Setting With a Single Resistor
  • Integrated 0.6 Ohm Isolating MOSFET Switch With Inrush Current Limit
  • Power Off DC-DC Input Capacitor Discharge
  • 100 kHz to 500 kHz Adjustable DC-DC Switching Frequency
  • DC-DC Frequency Can Be Synchronized to External Clock
  • Supports Low Power Mode Operation for Higher Efficiency 50% Maximum Duty Cycle
  • Soft-start Circuit to Control The Output Voltage Rise Time
  • Two out-of-phase driver stages for efficient synchronous rectification or active clamp
  • PoE Port Input UVLO with Programmable Threshold and Hysteresis
  • Internal Differential Amplifier Simplifying Non-isolated Step Down Converter
  • Over Load and Short Circuit Protection
  • RoHS Compliant & Pb-FreeRemarks
  • Refer Page no-11L1=10uH,L2=0.33uH,LNp=18uH,T2 are used.
  • Refer Page no-12L1=10uH,L2A=L2B=47uH


  Order Code SPEC Product series L
RDC typ.
Montageart Samples
7440700047 PDF WE-TPC SMT Tiny Power Inductor 4.7 3 2.2 37 65 SMT
7440690010 PDF WE-TPC SMT Tiny Power Inductor 1 3.6 3.8 21 90 SMT

Other applications and Würth Elektronik products for this IC

  • PD70201
    Topology: Flyback, Input Voltage (min.): 42.00 V, Input Voltage (max.): 57.00 V, Switching Frequency (min.): 100.00 kHz, Switching Frequency (max.): 500.00 kHz, Output 1: 12.00 V / 2.100 A, Output 2: 5.00 V / 5.000 A