Ac2 4-Bay Charging Dock - Intermec CK30 Service Manual

Chapter 4 — Theory of Operation

AC2 4-Bay Charging Dock

102
Temperature monitoring is done using a voltage divider formed by R1,
R17 and a NTC thermistor (RT1). If the battery voltage is at a value that
the BQ2954 identifies as being below the reference voltage, and the
ambient temperature is within acceptable limits then a charge cycle will
begin.
When a charge cycle begins, pin 14 on the BQ2954 is modulated at
100kHz. This pin controls a buck switcher formed by Q6, D1, and L2.
This switcher is set to provide a constant 8.4 VDC from the 12 VDC
supply. Once the battery has reached 8.4V (+100 mV–10 mV) then the
BQ2954 switches to the constant voltage phase of the charge cycle. During
this phase the BQ2954 slowly ramps down the charge current until the
designed trip point (Imax/15) is reached. At this point charge current is
terminated and the charge cycle is complete.
AC1 Input Power Requirements
The AC1 requires 12 VDC at 4A. The 073573 power supply is qualified
for use with the AC1.
The AC2 can charge four CK30 units at the same time. The AC2 uses the
same PCB as the AD2. The only difference is that all communications
related circuitry has been removed. The only function of the AC2 is to
charge the battery of up to four CK30s simultaneously.
A CK30 that is inserted into the AC2 is powered directly from the 12V
supply. J6, J14, J22, and J30 are the contacts by which power is transferred
to each of the four CK30s.
AC2 Charging
The charging design is the same as the AD2. Refer to "AD2 Charging" for
a detailed description of the charging algorithm.
AC2 Input Power Requirements
The AC2 requires 12 VDC at 4A. The 073573 power supply is qualified
for use with the AC2.
CK30 Handheld Computer Service Manual