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DSB75 Development Support Board Rev. B1 Hardware Description

Strictly confidential / Released

DSB75_hd_v08 Page 58 of 94 29.09.2005

3.14.1 Internal Supply Voltages

This section describes the internal supply voltages generated by the power supply unit of

DSB75. A simplified block diagram of the power supply concept is shown in section 3.14.

Table 23: Description of power supply units

Power Supply Unit Description

General supply 5V0

(see Figure 34)

DSB75 accepts an input voltage between 9V and 15V DC on jacks X400

and X401.

These ports are protected against polarity reversal by a simple diode

V400.

To reduce power dissipation, a DC/DC converter N400 provides a

constant voltage of 5.0V. This voltage is used for supplying 3 LDOs and

the audio section with power and is available for battery charging,

supplying I2C and DAI interface.

Audio supply (5V0_I)

(see Figure 35)

Audio power supply is decoupled with simple low pass filters from 5V0

supply.

GSM module supply

(3V3_4V5 or BATT+)

(see Figure 36)

For supplying the GSM module with regulated voltage the toggle switch

S601 must be flipped down.

In addition, the LDO for battery voltage N410 is adjustable for three

voltage values (please refer to Table 29 and Figure 39).

Two capacitors at 4700µF suppress voltage drops and ripples at GSM

burst.

For remote control, the jumper X405 has to be set to shut down the

voltage.

Power supply to digital

part of DSB75

(3V0)

(see Figure 32)

The simple LDO (N411) regulates the 5V0 voltage down to 3.0V.

This voltage supplies the digital devices (RS232 driver, LED-driver).

Digital IO supply

(VDD)

(see Figure 32)

The simple LDO (N412) regulates the 5V0 voltage down to 2.9V but this

voltage is enabled by inverted PWR_IND signal. Therefore VDD is only

present when the GSM module is operating.

This voltage supplies the digital IO pull-up resistors, EEPROM, SD card

and the digital interfaces: I²C, SPI, DAI.

GND

L401

47U

3N3

C402

ZJYS51R5-2PT

L400

V400

1SR154-400

2-POL

X400

2-POL

X401

LM2596S-ADJ

N400

GND1

GND2

OUT

GND

V401

40V/1A

GNDGND

8K25

661µF

R401

2K7

R400

GND

4812µF

C403,410,413

470,473

5V0

C400,401,405

Figure 34: Input circuit schematic (5V DC/DC converter) for power supply

1 2 ... 53 54 55 56 57 58 59 60 61 62 63 ... 93 94

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