ST ST7540, Примечание к применению

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Board description AN2451
36/55 Doc ID 12791 Rev 3
5.7 Power supply
The ST7540 reference design includes a specifically designed Switching Mode Power
Supply (SMPS) circuit, based on the ST VIPer12AS-E device.
The VIPer12AS-E is a smart power device with a current mode PWM controller, a startup
circuit and protections integrated in a monolithic chip using VIPower M0 technology. It
includes a 27
Ω
Mosfet with 730 V breakdown voltage and a 400 mA peak drain current
limitation. The switching frequency is internally fixed at 60 kHz, in order to provide a good
compromise between EMI performances and magnetic parts dimensioning.
The internal control circuit offers the following benefits:
● large input voltage range on VDD pin accommodates changes in supply voltage
●
automatic burst mode in low-load condition
●
overload and short-circuit protection in hiccup mode
The power supply is designed in isolated flyback configuration. Secondary regulation,
implemented through an optocoupler and a Zener diode, takes the requested output
tolerance for the specified application into account.
The main specifications are listed in Table 10 .
41 RxTx Receiving or transmission selection µC
44 UART/SPI Host Interface selection µC
45 CLR/T Serial data clock Modem
46 WD Watchdog timer reset µC
48 BU/THERM
- Rx mode: band-in-use detection signal
- Tx mode: thermal event signal
Modem
49 TxD Serial data input µC
Table 8. 50-pin connector analog signals
Pin number Signal name Description Generated by
8 ANALOG_IN Analog input (for
μ
C processing) -
Table 9. 50-pin connector power connections
Pin number Signal name Description Generated by
2 PLM_10 V 12 V power supply PLC Board
4 VDD 3.3 V / 5 V power supply Modem
5 VDDF_Force Force microcontroller digital level to VDDF PLC Board (VDC)
6 VDDF Digital power supply Modem (VDD)
22,34 GND Ground -
Table 7. 50-pin connector digital signals
Pin number Signal name Description Generated by