Specifications

WM_PRJ_Q2501_PTS_002 - 001
March 2004
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3.1.1.2 Design requirements
A Careful attention should be paid to:
 Quality of the power supply:
o linear regulation (recommended) or PWM (Pulse Width
Modulation) converter (usable) are preferred for low noise.
o PFM (Power Frequency modulation) or PSM (Phase Shift
Modulation) systems must be avoided.
 Capacity to deliver high current peaks in a short time (bursted radio
emission).
 The VBATT line must support peak currents with an acceptable voltage
drop which guarantees a VBATT minimal value of 3.4 V (lower limit of
VBATT).
For PCB design constraints related to power supply tracks, ground planes and
shielding, refer to paragraph 4.2.2.
3.1.1.3 Decoupling of power supply signals
Decoupling capacitors on VBATT lines are imbedded in the module. So it
should not be necessary to add decoupling capacitors close to the module.
However, in case of EMI/RFI problem, VBATT signal may require some EMI/RFI
decoupling: parallel 33 pF capacitor close to the module or a serial ferrite bead
(or both to get better results).
In case a ferrite bead is used, the recommendation given for the power supply
connection must be carefully followed (high current capacity and low
impedance).