ICD-MS1 (serv.man2) - Sony Audio Service Manual (repair manual). Page 11

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11

 

 
The basic operation of the power supply circuit of this unit remains the same in both when it is operated on an alkaline battery and when it is operated on an AC adapter. 
Because this unit does not have the POWER switch, the system controller IC722 controls supply of the power to each block in accordance with the modes that are called as the 
sleep mode and wakeup mode, and in accordance with the operating statuses such as recording and playback for lower power consumption. How the respective power 
supplies are controlled and operated, are described as follows. Refer to Section 2-1. "Discriminating Power Supplies" for the differences due to connection of the different power 
supplies to this unit. 
 
‹

 
1.   First, the UNREG 2.5 [V] is supplied to the unit from either the battery or AC adapter. This voltage is used as the power voltage for the POWER AMP IC168, but the system 

controller IC722 controls operation of IC168 in accordance with the operating status of the unit. 

 
2.   The UNREG 2.5 [V] passes through the over-discharge protection circuit consisting of IC521 and Q521, and is input to pin-3 [CE] of the POWER CONTROL IC522 and 

pin-3 [CE] of the +3.3 [V] REG IC524 as the selection voltage (chip enable signal). 

 
3.   When the POWER CONTROL IC522 enters the active operating state as it receives the CE signal, it outputs the PWM signal of about 100 kHz from pin-5 [EXT] to drive 

Q522, and outputs the VCC 3.5 [V] at the cathode of the diode D521. The VCC 3.5 [V] is then input to pin-2 [VIN] of the +3.3 [V] REG IC524. At this time, duty cycle of the 
PWM signal output from pin-5 [EXT] is varied by the input voltage so that the stable PWM output signal can be obtained. 

 
4.  As the +3.3 [V] REG IC524 receives the VCC 3.5 [V], it outputs the SYS_VCC 3.3 [V] from pin-5 [VOUT] and supplies the power to the system controller IC722, timer IC721, 

EEP ROM IC723 and S-RAM IC727. The +3.3 [V] power is also supplied to the LCD block LCD720 but the system controller IC722 controls the LCD display operation in 
accordance with the operating status of the unit. 

 

5

3

2

1

5

2

3

3

1

1

121

UN REG 2.5[V]

L521

D521

VCC 3.5[V]

Q522

IC521,Q521

TO IC168 POWER AMP.

 

EXT

VDD

VOOT

CE

IC522
POWER CONTROL

IC524 +3.3[V]REG

SYS_VCC 3.3[V]

CE

VIN

VOUT

IC726
RESET

IC721
TIMER

VIN

VOOT

D721

XRST

TO
IC723 EEPROM
IC727 S-RAM
LCD720

IC722
SYSTEM
CONTROLLER

VCC

OUT

Over-discharge
protection circuit

 

Fig 2-4 Supplying power to the system controller and timer (RTC)