User's Manual
Table Of Contents
- Contents
- Figures
- Tables
- Document History
- Introduction
- Product concept
- Application Interface
- Antenna interface
- Electrical, reliability and radio characteristics
- Mechanics
- Reference Approval
- List of parts and accessories
MC46 Hardware Interface Description
DRAFT
MC46_HD_V02.8xb Page 25 of 98 21.08.2003
3.2.2 Minimizing power losses
When designing the power supply for your application please pay specific attention to power
losses. Ensure that the input voltage V
BATT+
never drops below 3.2 V on the MC46 board, not
even in a transmit burst where current consumption can rise to typical peaks of 2A. It should
be noted that MC46 switches off when exceeding these limits. Any voltage drops that may
occur in a transmit burst should not exceed 400mV. For further details see Chapter 5.4.
The best approach to reducing voltage drops is to use a board-to-board connection as
recommended, and a low impedance power source. The resistance of the power supply lines
on the host board and of a battery pack should also be considered.
Note: If the application design requires an adapter cable between both board-to-board
connectors, use a flex cable as short as possible in order to minimize power
losses.
Example: If the length of the flex cable reaches the maximum length of 200mm, this
connection may cause, for example, a resistance of 50m! in the BATT+ line and
50m! in the GND line. As a result, a 2A transmit burst would add up to a total
voltage drop of 200mV. Plus, if a battery pack is involved, further losses may
occur due to the resistance across the battery lines and the internal resistance of
the battery.
Figure 2: Power supply limits during transmit burst
The input voltage V
BATT+
must be measured directly at the test points on the MC46 board (TP
BATT+ and TP GND illustrated in Figure 40).
3.2.3 Monitoring power supply
To help you monitor the supply voltage you can use the AT^SBV command which returns the
voltage measured at TP BATT+ and GND.
The voltage is continuously measured at intervals depending on the operating mode on the
RF interface. The duration of measuring ranges from 0.5s in TALK/DATA mode to 50s when
MC46 is deregistered. The displayed voltage (in mV) is averaged over the last measuring
period before the AT^SBV command was executed.
For details please refer to [1].
Transmit
burst 2A
Transmit
burst 2A
Ripple
Drop
min. 3.2V
BATT+