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DSB75 Development Support Board Rev. B1 Hardware Description

Strictly confidential / Released

DSB75_hd_v08 Page 64 of 94 29.09.2005

3.14.5 Adjusting the V

BATT+

Supply Voltage for the GSM Module

For test purposes, the V

BATT+

voltage supplied to the GSM module can be adjusted using

jumpers and variable resistors.

The jumpers X410 and X411 serve to set the V

BATT+

voltage range, and the variable resistors

R414 and R415 are used to adjust the supply voltage within the selected range. Therefore,

first set the range (lower limit or normal). Then turn the screw of the associated resistor R414

or R415 to reduce or increase the desired voltage, while measuring the module’s input

voltage at its test points BATT+ and GND. Take into account that voltage drops and ripples

may occur. The maximum voltage is set only via the jumpers, it cannot be adjusted via the

resistors.

Figure 39 shows the location of the jumpers and variable resistors on the DSB75. The

settings for adjusting the supply voltage of the GSM module are described in Table 29.

Table 29: Adjusting BATT+ voltage (3V3_4V5)

Voltage

type

Jumper

X410

Jumper

X411

Variable

Resistor

Voltage range Default setting

Upper limit closed closed --- 4.5V +-5% fixed

Normal closed open R415 2.85V. to 4.5V 4.1V +- 5%

Lower limit open closed R414 2.85V. to 4.5V 3.5V +- 5%

Figure 39: Location of jumpers and resistors for

adjusting BATT+ voltage (3V3_4V5)

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Siemens ET7 Series Spezifikationen Seite 64