DSC-F1 (serv.man2) - Sony Digital Camera Service Manual (repair manual). Page 8

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Refer to the service manual for the circuit diagram.

• Starting the 3.2V REG

When the power supply is connected, the UNREG voltage from Pin !¶ of CN304 is supplied to the HV board. At this time,

Q309 turns ON instantaneously, Pin 2 of the 3.2V REG (IC305) becomes L, and IC305 is started.

When IC305 outputs the voltage for the microprocessor, and the microprocessor is started, Q309 is set to ON continuously

by the H output of the SLEEP terminal (Pin ^¶ of IC301) to maintain the IC305 operations.

• Output of voltage for HI microprocessor (3.2V)

When the UNREG voltage is lower than 3.7V, it is stepped up by the switching of Pin 8 of IC305. When the UNREG

voltage is higher than 3.7V, it is stepped down by the series regulator inside IC305. The 3.2V output from Pin 5 of IC305
becomes the voltage for the HI microprocessor.

When the mode switch is OFF and the battery is not charged, the output of the voltage for the HI microprocessor is stopped

periodically by IC304. When the microprocessor voltage drops below 2.8V, Pin 1 of IC304 becomes L, and the operations of
the 3.2V REG (IC305) are restarted. Consequently, the microprocessor voltage changes between 2.8V and 3.2V periodically.

• Detection of decrease in UNREG voltage

When the power supply voltage (UNREG voltage) drops below 2.8V, Pin 1 of IC306 becomes L, and is detected by the

XMAINSLP terminal (Pin &• of IC301) of the microprocessor. As a result, IC301 sets into the sleep mode, and the power of
the unit cannot be turned ON.

When a voltage input is not present at all since the power supply is pulled out, Q314 turns ON by the back up capacitor

voltage to keep the XMAINSLP terminal at L. As a result, the microprocessor continues the sleep operation.

• Voltage control during sleep mode

In the sleep mode, the 2.8V REG (IC304) controls the ON/OFF of IC305, so that the voltage for the microprocessor is

controlled between 2.8V and 3.2V. For this reason, the microprocessor voltage changes periodically in the sleep mode.

• Low voltage operation of microprocessor voltage

When the battery terminal voltage becomes 1.6V, the HI microprocessor voltage also drops.
When the voltage for the HI microprocessor drops below 2.6V, it is detected by the 2.6V DET (IC303), and the XHIRESET

terminal becomes L, and as a result, the HI microprocessor is reset. At the same time, the time is also reset.

• Backup capacitor for clock (super capacitor)

When all the external power supplies are disconnected, voltage is supplied from the backup capacitor (C072) to the HI

microprocessor. At this time, Q310 will go OFF so that the voltage is not supplied from C072 to the 3.2V REG (IC305).