User's Manual
Date: 2010/02/04
Version: 1.0
Status: Released
8/22 ACM8068 HW Application Manual V1.0 ©Copyright 2010, AMOD Technology
Figure 3: Voltage drop versus distance
3.3 DesignRecommendation
Additional notes to the design of power supply circuit:
• Quality attention must be paid to the power supply circuit for their resistance
value and burst current.
• The circuit line between power supply input to VBAT should try to avoid
interference of other source of signals.
• Decoupling capacitors.
3.3.1 PowerSupplySelection
Power supply selection must fulfill following conditions:
• By using large capacity and low ESR capacitors, the system can avoid
influence of over burst current.
• The power sources must have good ripple rejection. In another word, the ripple
value of current input to VBAT should be as low as possible.
• Low output resistance.
3.3.2 PowerSupplyCircuitRecommendation
Interferences of other signal sources to the power supply must be avoided.
VBAT connection pins: Pins 38, 39
• Track line width between the power supply and GSM VBAT input should be
3mm.
• The power circuit lines should be separated from other signal lines (e.g.
Audio/SIM/UART… etc) by ground
• Make sure to avoid having any signal lines going under the power lines.