Ad1 1-Bay Communications Dock - Intermec CK30 Service Manual

AD1 1-Bay Communications Dock

CK30 Handheld Computer Service Manual
The AD1 charges a single CK30 battery while on the unit. It also provides
a DB9 male connector for serial communications, an 8-pin RJ45
connector for 10/100 Ethernet communications, a Type-B USB connector
for USB communications and a 26-pin JAE connector for interfacing with
the CK30. Refer to "Connector Pin-Outs" on page 96 for the connector
pin-outs. All of these communication methods are handled by the CK30;
the connectors on the AD1 are simply used for passing the signals to and
from the CK30.
The 26-pin JAE connector is a right-angle connector that is mounted on a
separate PCB; it interfaces to the AD1's main PCB through two 10-pin
headers (J4 and J5).
A CK30 that is inserted into the AD1 is powered directly from the 12V
supply. J9 is the contact by which power is transferred to the CK30.
AD1 Charging
U1 (TI BQ2954) controls all aspects of charging for the AD1. It uses a
constant current/constant voltage-charging algorithm. The AD1 is
designed to charge the CK30 battery pack with a maximum charge current
of 1.25A. The sense resistor (R15) is what sets the maximum charge
current (Imax = 250 mV/R15). The AD1 is also designed to only allow
charging between 0ºC and 45ºC ±7ºC. A battery that has been discharged
through normal use on a CK30 recharges in less than three hours on the
AD1.
J10, J11, and J12 are the contacts by which the CK30 battery interfaces to
the charging circuitry. The voltage divider formed by R16 and R17 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.
Temperature monitoring is done using a voltage divider formed by R18,
R19 and a NTC thermistor (R23). 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 begins.
When a charge cycle begins, pin 14 on the BQ2954 is modulated at
100kHz. This pin controls a buck switcher formed by Q4, D5 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 (+100mV -10mV) 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/20) is reached. At this point charge
current is terminated and the charge cycle is complete.
The BQ2954 uses the current mirror (U6) to measure the charge current.
This measurement is used to compare against the designed trip point
(Imax/20).
Chapter 4 — Theory of Operation
99