ST7538P STMicroelectronics, ST7538P Datasheet - Page 24

• Manufacturer Part Number: ST7538P
• Description: Telecom Line Management ICs 1/2 Duplex FSK Modem
• Manufacturer: STMicroelectronics
• Type: Single Chipr

Specifications of ST7538P

• Product: Modem Chip
• Supply Voltage (max): 5.25 V, 12.5 V
• Supply Voltage (min): 4.75 V, 7.5 V
• Supply Current: 5 mA, 370 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Package / Case: TQFP-44
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ST7538
4.4 Zero Crossing Detection
The Mains Voltage Zero Crossing can be detected, through a proper connection of ZCIN to the Mains.
ZCIN comparator has a threshold fixed at SGND. ZCOUT is a TTL Output forced High after a positive
zero-crossing transition, and low after a negative one.
Setting the Bit 11 inside the Control Register to “1” the transmission is automatically synchronized to the
mains positive zero-crossing transition. This function is achieved turning on the PLI when RX/TX is low
and delaying the CLR/T first transition until the first zero-crossing event. The automatic synchronization
procedure can work only if the synchronous interface is programmed. If asynchronous interface is in use
the Zero Crossing synchronization can be achieved managing the ZCOUT line.
Figure 23. Synchronous Zero-Crossing Transmission
4.5 Output Clock
MCLK is the master clock output. The clock frequency sourced can be programed through the control reg-
ister to be a ratio of the crystal oscillator frequency (Fosc, Fosc/2 Fosc/4). The transition between one fre-
quency and another is done only at the end of the ongoing cycle.
4.6 Reg OK
REGOK allows to detect an accidental corruption of the Control Register content. If a register content cor-
ruption is detected, REGOK goes to "1". REGOK function is disabled during a control register writing ses-
sion.
4.7 Under Voltage Lock Out
The UVLO function turns off the device if the PAVdd voltage falls under 4V. Hysteresis is 340mV typically.
4.8 Thermal Shutdown
The ST7538 is provided of a thermal protection which turn off the PLI when the junction temperature ex-
ceeds 170°C ±10% . Hysteresis is around 30°C.
When shutdown threshold is overcome, PLI interface is switched OFF.
Thermal Shutdown event is notified to the HOST controller using TIMEOUT line. When TIMEOUT line is
High, ST7538 junction temperature exceed the shutdown threshold (Not Lached).
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ZCOUT
CLR/T
ZCIN
RxTx
TxD
ZC
DEL
D03IN1423
t