PM8800 STMicroelectronics, PM8800 Datasheet - Page 28
![no-image](/images/manufacturer_photos/0/6/637/stmicroelectronics_sml.jpg)
PM8800
Manufacturer Part Number
PM8800
Description
Integrated IEEE 802.3af compliant PoE-PD interface and PWM controller with support of external source
Manufacturer
STMicroelectronics
Datasheet
1.PM8800.pdf
(35 pages)
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
PM8800A
Manufacturer:
ST
Quantity:
20 000
Company:
Part Number:
PM8800A-WGI
Manufacturer:
ST
Quantity:
3 100
Company:
Part Number:
PM8800ATR
Manufacturer:
ON
Quantity:
300 000
Part Number:
PM8800ATR
Manufacturer:
ST
Quantity:
20 000
PWM section
6.6
6.7
28/35
Figure 18. Internal short circuit
Ch1 = 5 Vout, Ch2 = SoftStart, Ch4= I input
Leading edge blanking
The sense current waveform often observes large spikes on the leading edge. This is due to
rectifier recovery and/or interwinding capacitance in the power transformer. If not
attenuated, this transient can prematurely terminate the output pulse. A simple RC filter -
whose time constant is approximately equal to the spike duration - is usually adequate to
suppress this spike.
An internal blanking time has been anyway integrated in order to prevent false overcurrent
detection to terminate the PWM waveform. This is done by a masking logic, active for
duration of 70 ns after the turn-on time of the primary side MOSFET.
Thermal protection
PM8800A has a two level thermal protection referred to the internal junction temperature.
First limit is set to 130 °C and limits the current into the hot-swap MOSFET to 140 mA every
time the voltage difference between VSS and GND is higher than 3 V.
The second limit is set to 160 °C and is always active. When this threshold is overtaken, the
hot-swap is opened and the PWM controller is switched-off.
1
2
3
4
PM8800A