Ac1 4-Slot Battery Charger - Intermec CK30 Service Manual

AC1 4-Slot Battery Charger

CK30 Handheld Computer Service Manual
During this phase the BQ2954 slowly ramps down the charge current
until the designed trip point (Imax/20) is reached. At this point charge
current is terminated and the charge cycle is complete.
The BQ2954 uses the current mirror (U3) to measure the charge current.
This measurement is used to compare against the designed trip point
(Imax/20).
AD2 Ethernet Switch
The KS8995X is a fully independent five-port 10/100 Ethernet switch.
The switch is configured completely by resistor strapping per the
KS8995X datasheet.
Each of the four 26-pin JAE connectors is connected to a port on the
Ethernet switch. The fifth port is connected to the 8-pin RJ45 connector
(J1). J1 is the connector by which the end user connects to their Ethernet
network.
AD2 Input Power Requirements
The AD2 requires 12 VDC at 4A. The 073573 power supply is qualified
for use with the AD2.
The AC1 can charge four CK30 batteries (AB1) simultaneously.
AC1 Charging
The design was done based on our input; this makes the design of this
charger very similar to all the in-house designed CK30 chargers/docks.
This charger also uses the TI BQ2954 to control charging. The only
difference is that the BQ2954 is configured for "low-side current sensing"
as opposed to all the in-house designs which use "high-side current
sensing."
The AC1 has four identical charging circuits, one for each slot in the
charger.
U2 (TI BQ2954) controls all aspects of charging for the AC1. It uses a
constant current/constant voltage-charging algorithm. The AC1 is
designed to charge the CK30 battery pack with a maximum charge current
of 925 mA. The sense resistor (R27) is what sets the maximum charge
current (Imax = 250 mV/R27). The AC1 is also designed to only allow
charging between 0°C and 45°C ±7°C. A battery that has been discharged
via normal use on a CK30 recharges in less than five hours on the AC1.
J4 pins 1,2, and 3 are the contacts by which the AB1 battery interfaces to
the charging circuitry. The voltage divider formed by R22 and R21 is
used to notify the BQ2954 that a battery has been inserted. It is also used
to determine whether to begin charging based on the battery voltage and
an internal reference voltage in the BQ2954.
Chapter 4 — Theory of Operation
101