User's Guide

UC864-E-AUTO / AWS-AUTO Hardware User Guide

1vv0300795 Rev.11 – 2010/11/18

Considering the very low current during idle, especially if Power Saving function is

enabled, it is possible to consider from the thermal point of view that the device

absorbs current significantly only during calls.

If we assume that the device stays in transmission for short periods of time (let us

say few minutes) and then remains for quite a long time in idle (let us say one hour),

then the power supply has always the time to cool down between the calls and the

heat sink could be smaller than the calculated for 730mA maximum RMS current.

There could even be a simple chip package (no heat sink).

Moreover in average network conditions the device is requested to transmit at a

lower power level than the maximum and hence the current consumption will be less

than 730mA (being usually around 250mA).

For these reasons the thermal design is rarely a concern and the simple ground

plane where the power supply chip is placed can be enough to ensure a good thermal

condition and avoid overheating.

For the heat generated by the UC864-E-AUTO / AWS-AUTO, you can consider it to be

during transmission 2W max. This generated heat will be mostly conducted to the

ground plane under the UC864-E-AUTO / AWS-AUTO; you must ensure that your

application can dissipate heat

In the WCDMA/HSDPA mode, since UC864-E-AUTO / AWS-AUTO emits RF signals

continuously during transmission, you must pay special attention how to dissipate

the heat generated.

The current consumption will be up to about 730mA in HSDPA (680mA in WCDMA)

continuously at the maximum TX output power (24dBm). Thus, you must arrange the

PCB area as large as possible under UC864-E-AUTO / AWS-AUTO which you will

mount. You must mount UC864-E-AUTO / AWS-AUTO on the large ground area of

your application board and make many ground vias to dissipate the heat.

The peak current consumption in the GSM mode is higher than that in WCDMA.

However, considering the heat sink is more important in case of WCDMA.

NOTE:

NOTE: NOTE:

NOTE:

The average consumption during transmissions depends on the power level at which

the device is requested to transmit via the network. The average current

consumption hence varies significantly.

NOTE:

NOTE: NOTE:

NOTE:

The thermal design for the Power supply must be made keeping an average

consumption at the max transmitting level during calls of 730mA rms.