DSB75 Development Support Board Rev. B1 Hardware Description
Confidential / Released
DSB75_hd_v12
Page 66 of 96
2008-08-26
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 31.
Table 31: 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)
