ST7538Q datasheet(38/44 Pages) STMICROELECTRONICS

38 / 44 page

Auxiliary analog and digital functions

ST7538Q

38/44

6.5

Output clock

MCLK is the master clock output. The clock frequency sourced can be programed through

the control register to be a ratio of the crystal oscillator frequency (Fosc, Fosc/2 Fosc/4) or

can be disabled (off). The transition between one frequency and another is done only at the

end of the ongoing cycle.

6.6

Output voltage level freeze

The Output Level Freeze function, when enabled, turns off the Voltage Control Loop once

the ALC stays in a stable condition for about 3 periods of control loop, and maintains a

constant gain until the end of transmission. Output Level Freeze can be enabled using

Control Register bit 17 (Table 11). This function is available only using the Extended Control

6.7

Extended control register

When Extended Control Register function is enabled, all the 48 bits of Control Register are

programmable. Otherwise, only the first 24 bits of Control Register are programmable. The

functions Header Recognition, Frame Bit Count and Output Voltage Freeze are available

only if Extended Control Register function is enabled. Extended Control Register can be

enabled setting the Control Register bit 21(Table 11).

6.8

Reg OK

REGOK allows to detect an incomplete writing of the Control Register content (see

Section 5.6: Control register access on page 21) or an accidental corruption of the Control

session is performed.

6.9

Under voltage lock out

The UVLO function turns off the device if the PAVcc voltage falls under 4V. Hysteresis is

340mV typically.

6.10

Thermal shutdown

The ST7538Q is provided of a thermal protection which turn off the PLI when the junction

temperature exceeds 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, ST7538Q junction temperature exceed the shutdown threshold (Not

Leached).

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