User's Manual

1323x Remote Extender Motherboard

1323x Development Hardware Reference Manual, Rev. 1.0

5-6 Freescale Semiconductor

3. Battery Operation - a battery holder that accommodates two AA batteries is mounted on the

non-component (back) side of the board and provides for battery operation.

– If either the USB or external DC source is present, the battery source is disabled by

MOSFET transistor Q3

– The sources are all isolated and protected by Schottky diodes

– The minimum effective battery operating voltage is controlled by the use the FTDI

FT232RQ USB <> UART device - leakage current back through the FT232RQ UART

connections to the MC13233 on the MRB can cause the Q3 MOSFET to partially turnoff at

battery voltage below approximately 2.7-2.8 Vdc.

NOTE

To avoid current leakage through the USB device and lower minimum

battery operating voltage for battery-only operation, remove the following

jumpers:

• P1, Pins 7-8

• P1, Pins 11-12

• P1, Pins 17-18

• P1, Pins 21-22

NOTE

When battery operation is used, the temperature range of the two board

system should be limited to within the specified temperature range of the

battery technology. Table 5-1 limits temperature range from 0 °C to +50 °C

when battery operation is applied.

Table 5-2 lists the voltage source attributes.

Table 5-2. 1323x-REM Voltage Sources

Source Connector

Input Voltage

Range

Description

USB Port USB Type-B J15 4.4 V - 5.25 V • The input voltage range is set to the USB specification value

• The voltage can be supplied by either a standard USB cable

connection or an AC to DC power adaptor that uses the USB

connector J15

• If a power adaptor is in use, the USB serial port cannot be

used

External DC Supply 1x2 Pin Hdr J14 2.3 V - 6 V The input voltage range is determined by the U8 regulator and

the diode isolation circuit

Two AA Batteries Battery Holder 2.0 V - 3.1 V

The minimum operating battery voltage is determined by use model, see Note, Section 5.2.1, “Power Management”

• The input voltage range reflects the usable range of alkaline

cells and the voltage drop incurred by the diode isolation

circuit.

• The battery source is disabled if another source is connected