SimCom SIM8905A User Manual page 8

2. Detail Block Diagram
720P LCD
Primary Camera (8MP)
Secondary Camera (5MP)
USB HS (Support OTG)
UIM Card1
UIM Card2
SD Card
TP/Sensor/Cam/others
Keypad Buttons
VBUS_5V
VBAT
Vibrator
ADC
Headset
Microphone
Earpiece
Speaker
3. Interface Application
Power Supply
The power supply pins of SIM8905A include VBAT_RF and VBAT_BB. VBAT_RF directly supplies the power
to RF PA; VBAT_BB supplies the power to the baseband system. The power supply of SIM8905A ranges from
3.4V to 4.4V, and 3.9V is recommended. It must be able to provide sufficient current up to 3A for the high-power
transmitting.
If the DC input voltage is +5V and customers do not care about the power efficiency, a high-current low-dropout
regulator is recommended. Figure 4 is the reference design.
DC INPUT
+
C101
100uF
Note: To ensure a proper behavior of the regulator under light load, an extra minimum load (R103 in Figure 4)
is required, because the current SIM8905A consumed is very small in sleep mode and power off mode. For
more details about minimum load, please refer to specification of MIC29302.
4 Lanes DSI
2 Lanes CSI
1 Lanes CSI
AP
USB
UIM1
Quad A7 w/ 512K L2
UIM2
Camera ISP/VFE/Jpeg HW
SDC2
Display Processor
I2C
Video
SPI
Graphics
UART * 2
Keypad Buttons
Peripherals
GPIO
Linear
SPMI BUS
Charger
Output Power
Management
PM8909
PDM BUS
Codec Digital
CODEC
19.2M XO
Figure 3: Block diagram of SIM8905A
U101 MIC29302
2
Vin
1
C102
On/Off
1uF
PWR_CTRL 3
Figure 4: LDO power supply reference circuit
Smart Machine Smart Decision
Modem
Jolokia
4G/3G/2G MODEM
WWAN RX I/Q
Core
GSM Phase
WWAN TX I/Q
MODEM/Voice
Processor
GNSS I/Q
GNSS
Baseband
MSM8909
BT/WIFI
Baseband
Memory Support
4
Vout
5
R101
+
FB
C103
100K
330uF
R102
47K
8
Front End
3 rd party
RFFE PA+SW
DIVERSITY
SWITCH
MODULE
WTR4905
RFFE
MMMB
Power
Amplifier
RFFE Modele
Note2
EBI1
eMMC flash +
LPDDR3
SDC1
VBAT
R103
C104
470R
100nF
MAIN
DRX