Copyright ©2007 NavSync Ltd.All Rights Reserved
Specifications subject to change without notice.
CW25 Software User Manual
Page
11 of 50
Rev 03
Date: 06/16/08
4. SIGNAL DESCRIPTION
The signals on the CW25 are described in the table below. All Test, Control and I/O ports are CMOS 3.3V compatible un-
less specified otherwise.
4.1 Power Signals
RF_3V3
Type: Power
Direction: Input
Pin: 19
The RF supply input. This 3.3V ± 10% input supplies the 3.0V LDO regulator in the RF
section of the CW25. It is important that this supply is well filtered with no more that 50mV
peak to peak noise with respect to RF_GND.
RF_GND
Type: Power
Direction: Input/Output
Pins: 18, 23, 25
The RF input ground connect to common ground. This is the return path for the RF_3V3
supply and the ground for the antenna feed. The RF_GND must be tied to the DIG_GND
externally to the CW25.
RFV_OUT
Type: Power
Direction: Output
Pin: 17
The output from the LDO regulator (3.0V) that is powered by the RF_3V3 signal. This
supplies the power to the RF subsystem of the CW25. This may also be used to power
external RF components but care must be taken not to inject noise onto this signal. No more
than an additional 30mA may be taken from this signal by external circuitry.
ANT_SUPPLY
Type: Power
Direction: Input
Pin: 26
The antenna supply voltage. This may be used to supply power to the RF_IN signal, for use
by an active antenna. The maximum voltage should not exceed ±15V and the current should
be limited to 50mA to prevent damage to the CW25.
DIG_3V3
Type: Power
Direction: Input
Pin: 36
The digital supply input. This 3.3V ± 10% input supplies the I/O ring of the BB25IC chip and
the LDO regulator in the digital section of the CW25. It is important that this supply is well
filtered with no more that 50mV peak to peak noise with respect to DIG_GND.
DIG_1V8
Type: Power
Direction: Input
Pin: 34
The 1.8V ± 5% digital core supply for the BB25IC. This is normally connected directly to the
+1V8_OUT signal. However, if an external 1.8V ± 5% is available, a lower overall system
power consumption may be achieved by using an external supply.
+1V8_OUT
Type: Power
Direction: Output
Pin: 33
The 1.8V output from the LDO regulator that is powered by the DIG_3V3 signal. Normally,
this is connected to the DIG_1V8 signal. This loops back the regulated 1.8V to run the
processor core. If not connected the core will not run. This may also be used to power
external logic but care must be taken not to inject noise onto this signal. No more than an
additional 50mA may be taken from this signal by external logic.
DIG_GND
Type: Power
Direction: Input/Output
Pin: 35
The digital ground. This is the return path for the DIG_3V3 supply and the ground reference
for all the digital I/O. The DIG_GND must be tied to the RF_GND externally to the CW25.
VBATT
Type: Power
Direction: Input/Output
Pin: 27
The battery backup supply. The CW25 has an on board Real Time Clock (RTC). This is
powered from the VBATT signal. A supply of typically 3V (greater than 2.5V and less than
DIG_3V3) should be applied to this signal. This signal can be left floating if not required. The
input has a blocking diode and so rechargeable batteries will need an external charging
circuit. Typically, a 1K resister in series with this signal and the external battery will provide
an easy method of measuring the current consumption from VBATT during test.
