Motorola 8900 User Manual - Page 34

Power Supply, Power Supply Design

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Power Supply Power Supply The C24 power supply must be a single external DC voltage source of 3.3V to 4.2V. The power supply must be able to sustain the voltage level during a transmit current surge, which may reach 600 mA. The C24 interface connector has 8 contacts for the main power supply, as described in Table 2-2. All these contacts must be used for proper operation. Table 2-2: Power Supply Signals Pin # 1-4 Signal Name GND 5-8 VCC Description Main ground connection for C24 module. DC supply input for C24 module. VIN = 3.3 V to 4.2 V IRMS = 600 mA during transmission Power Supply Design Special care must be taken when designing the power supply of the C24. The single external DC power source indirectly supplies all the digital and analog interfaces, but also directly supplies the RF power amplifier (PA). Therefore, any degradation in the power supply performance, due to losses, noises or transients, will directly affect the C24 performance. It is recommended that any voltage drops during transmission will not exceed 300mV, measured on the C24 interface connector. In any case, the C24 supply input must not drop below the minimum operating level during transmission. Dropping below the minimum operating voltage may degrade the module performance. To minimize the losses and transients on the power supply lines, it is recommended to follow these guidelines: • Use a 100 uF, or greater, low ESR capacitor on the C24 supply inputs. The capacitor should be located as near to the C24 interface connector as possible. • Use low impedance power source, cabling and board routing. • Use cabling and routing as short as possible. • Filter the C24 supply lines using filtering capacitors, as described in Table 2-3. Table 2-3: Recommended Power Supply Filtering Capacitor Usage Description 100 uF Transmit current serge Minimizes power supply losses during transmission. 10 nF, 100 nF Digital switching noise Filters digital logic noises from clocks and data sources. 10 C24 Module Hardware Description December 15, 2008

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Power Supply
10
C24 Module Hardware Description
December 15, 2008
Power Supply
The C24 power supply must be a single external DC voltage source of 3.3V to 4.2V. The power
supply must be able to sustain the voltage level during a transmit current surge, which may reach
600 mA.
The C24 interface connector has 8 contacts for the main power supply, as described in
Table 2-2
.
All these contacts must be used for proper operation.
Power Supply Design
Special care must be taken when designing the power supply of the C24. The single external DC
power source indirectly supplies all the digital and analog interfaces, but also directly supplies the
RF power amplifier (PA). Therefore, any degradation in the power supply performance, due to
losses, noises or transients, will directly affect the C24 performance.
It is recommended that any voltage drops during transmission will not exceed 300mV, measured
on the C24 interface connector. In any case, the C24 supply input must not drop below the
minimum operating level during transmission. Dropping below the minimum operating voltage
may degrade the module performance.
To minimize the losses and transients on the power supply lines, it is recommended to follow
these guidelines:
•
Use a 100 uF, or greater, low ESR capacitor on the C24 supply inputs. The capacitor should
be located as near to the C24 interface connector as possible.
•
Use low impedance power source, cabling and board routing.
•
Use cabling and routing as short as possible.
•
Filter the C24 supply lines using filtering capacitors, as described in
Table 2-3
.
Table 2-2:
Power Supply Signals
Pin #
Signal Name
Description
1-4
GND
Main ground connection for C24
module.
5-8
VCC
DC supply input for C24 module.
V
IN
= 3.3 V to 4.2 V
I
RMS
= 600 mA during transmis-
sion
Table 2-3:
Recommended Power Supply Filtering
Capacitor
Usage
Description
100 uF
Transmit current serge
Minimizes power supply
losses during transmission.
10 nF, 100 nF
Digital switching noise
Filters digital logic noises
from clocks and data sources.