STW4810 datasheet(29/72 Pages) STMICROELECTRONICS

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STw4810

4 Functional description

Rev3

29/72

4.2.6

IT generation

STw4810 has three interrupt balls:

IT_WAKE_UP: with only VBAT supply, no other supply available, when a USB cable is plugged

this interrupt is activated to wake up the host or the modem, depends of application (active low).

USBINTn: This interrupt ball is dedicated to USB protocol and sent to multimedia processor

VDDOK: This ball has two functions:

- When high, it indicates that VIO_VMEM and VCORE output voltages are within the right

range and that the device internal temperature is below the maximum allowed temperature.

- When low, it indicates that output regulators (VCORE or VIO_VMEM) are not regulated

properly or PWREN = “0”, or that the temperature is above the allowed threshold (see

Thermal

shut-down section). The interruption source in the application register (address 11h) needs to

be checked.

4.2.7

Clock switching and control

This block generates the clock used by the DC/DC converter (USB charge pump, step-down

VIO_VMEM and step-down VCORE). STw4810 is able to sustain the master clock frequencies

of 26 MHz, 19.2MHz and 13 MHz. It can also sustain dedicated MASTER_CLK signal in the

frequency range of 750KHz to 1MHz. If the clock is not detected the internal oscillator is

automatically selected.

Note:

When present the Master clock should remain connected up to Sleep mode.

Figure 9.

Clock switching between master and internal clock (1)

INT_OSC

PON

INT_OSC_OK

MASTER_CLK_OK

PDN_INT_OSC

CONTROL_SWITCH

STEP_DOWN_CLK

Third rising edge after switching

internal clock

external clock

transition

* Phase delay is less than 90 between int and ext clock

MASTER_DIV_CLK

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