Vcoin; Table 31. Uvlo Thresholds; Table 32. Vcoin Pad; Table 33. Vcoin Interface Specification - Sierra Wireless AirPrime AR7558 Hardware Integration Manual

Hardware Integration Guide
Note: If the AirPrime AR7558 device has 6 UVLO events without a valid power down or reset sequence, it
enters a mode in which only the DM port enumerates on the USB.
Table 31. UVLO Thresholds
UVLO
6.2.

VCOIN

The AirPrime AR7558 provides an interface for a coin cell to maintain the internal RTC when VBATT
is removed from the AirPrime AR7558 device. Whenever VBATT is applied the RTC is powered from
the VBATT supply. The AirPrime AR7558 also supports charging of a coin cell if connected to this
interface.
Table 32. VCOIN Pad
Pad Name
AC11 VCOIN
The table below defines the specifications of this interface.
Table 33. VCOIN Interface Specification
VCOIN
DC Power Input Range
Current Draw
The table below defines the VCOIN charging specifications.
Table 34. VCOIN Charging Specifications
VCOIN Charging Specs
Target regulator voltage
Target series resistance
Coin cell charger voltage error
Coin cell charger resistor error
3
Dropout voltage
Ground current, charger enabled
VBAT = 3.6 V, T = 27 º C
VBAT = 3.2 to 4.2 V
1. Valid regulator voltage settings are 2.5, 3.0, 3.1, and 3.2 V.
2. Valid series resistor settings are 800, 1200, 1700, and 2100 Ω.
3. Set the input voltage (VBAT) to 3.5 V. Note the charger output voltage; call this value V0. Decrease the input voltage
until the regulated output voltage drops 100 mV (until the charger output voltage = V0 - 0.1 V). The voltage drop across
the regulator under this condition is the dropout voltage (Vdropout = VBAT - the charger output voltage).
4116922
Description
Rising threshold
Falling threshold
Minimum Duration below Falling threshold
Direction
Input /Output
Comments
1
VIN > 2.5 V, ICHG = 100 μA
2
ICHG = 0 μA
ICHG = 2 mA
IC = off; VCOIN = open
Rev 1.1
Function
Voltage Input/Charging output
Min
TBD
Min
TBD
800
-5
-20
–
–
–
Baseband Specification
Value Units
2.725 V
2.55 V
1.0 uS
If Unused
Leave Open
Typ Max
TBD TBD
1.1 2.0
Typ Max
TBD TBD
–
2100
–
+5
–
+20
–
200
–
4.5
–
8
January 21, 2015
Units
V
μA
Units
V
Ω
%
%
mV
μA
μA
31