hardware design v1.00
Table Of Contents
- Contents
- Version History
- 1 Introduction
- 2 SIM968 Overview
- 3 Package Information
- 4 GSM Application Interface
- 4.1 GSM Power Supply
- 4.2 Power on/down Scenarios
- 4.3 Power Saving Mode
- 4.4 Charging Interface
- 4.5 RTC Backup
- 4.6 Serial Interfaces
- 4.7 Audio Interfaces
- 4.8 SIM Card Interface
- 4.9 LCD Display/SPI Interface
- 4.10 Keypad Interface
- 4.11 ADC
- 4.12 RI Behaviors
- 4.13 Network Status Indication
- 4.14 General Purpose Input/Output (GPIO)
- 4.15 External Reset
- 4.16 PWM
- 4.17 I2C Bus
- 4.18 GSM Antenna Interface
- 5 GNSS Application Interface
- 6 Electrical, Reliability and Radio Characteristics
- 6.1 Absolute Maximum Ratings
- 6.2 Recommended Operating Conditions
- 6.3 Digital Interface Characteristics
- 6.4 SIM Card Interface Characteristics
- 6.5 VDD_EXT Characteristics
- 6.6 SIM_VDD Characteristics
- 6.7 VRTC Characteristics
- 6.8 Current Consumption (VBAT = 3.8V)
- 6.9 Electro-Static Discharge
- 6.10 Radio Characteristics
- 6.11 Module label information
- Appendix
Smart Machine Smart Decision
SIM968_Hardware Design_V1.00 2013.02.25
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4.4.1 Battery Pack Characteristics
SIM968 has optimized the charging algorithm for the Li-Ion battery that meets the characteristics listed below.
z The maximum charging voltage of the Li-Ion battery pack is 4.2V and the recommended capacity is
1100mAh. The Battery packs with more than 1100 mAh capacity will take more time for charging.
z The battery pack should have a protection circuit to avoid overcharging, deep discharging and over-current,
and the circuit should be insensitive to pulsed current.
z The internal resistance of the battery pack including protection circuit should be as low as possible. Its
recommended value does not exceed 150mΩ.
z The battery pack must be protected from reverse pole connection.
On the SIM968, the build-in circuit of the power management chipset monitors the supply voltage constantly.
Once the Under-voltage is detected, the SIM968 will be powered down automatically.
4.4.2 Recommended Battery Pack
Following is the specification of recommended battery pack:
Table 7: Specification of recommended battery pack
Items Description
Battery type Li-ion
Manufacturer Jiade Energy Technology
Normal voltage 3.7V
Capacity NORMAL 1100mAh
Charge Voltage 4.200±0.050V
Max Charge Current 1.0C
Charge Method CC / CV (Constant Current / Constant Voltage)
Max Discharge Current 1.0C (for continuous discharging mode)
Discharge Cut-off Voltage 3.0V/ cell
Internal resistance Initial≤130mΩ
4.4.3 Implemented Charging Technique
SIM968 has battery charging function. There are three pins related to the battery charging function: there are
VCHG, VBAT and TEMP_BAT/ADC0 pins. The VCHG Pin is driven by an external voltage, system can use this
Pin to detect a charger supply and provide most charging current through SIM968 module to battery when
charging is in fast charge state. VBAT pin gives charging current to external battery from SIM968 module.
TEMP_BAT Pin is for user to measure the battery temperature. Let this Pin open if battery temperature
measurement is not user’s design concern.
It is very simple to implement charging function, user just needs to connect the charger to the VCHG Pin and
connect the battery to the VBAT Pin.
SIM968 battery charging happens after detecting charger supply and the presence of battery. If there is no charger