
Functional Description
3 - 8
PMB 2347
preliminary
Wireless Components
Specification, August 1999
Synchronous Mode (only for RF):
In this mode counter programming is controlled by the R- and N-counters. The
serial data (exception: higher part of long control data format) is first written with
the Enable pulse to the corresponding shadow registers. From there the values
for R-counter, A-/N-counter and charge pump current values of short/long con-
trol data format are loaded into the corresponding data register when the N-
counter reaches zero+1“. Therefore the change of all counter states is syn-
chronised to the reloading of the N-counter to avoid additional phase error
caused by the programming. The transfer of the charge pump current values
into the corresponding data register is tied to the N-counter loading, but follows
the loading of the N-data register in the distance of one N-counter dividing ratio.
This guarantees that a new PD-current value becomes valid at the same time
when the counters are loaded with the new data.
Synchronous programming sequence:
1.Setting of synchronous counter programming by bit c13 of long control data
format.
2.Programming of the R-counter, and optional short control data format. With
the Enable signal data is loaded into the shadow registers.
3.Programming of the A/N-counter. Data is loaded into shadow registers, the
EN-signal starts the synchronous transfer to the data registers.
Synchronous data programming is of especial advantage, when large fre-
quency steps are to be made in a short time. For this purpose a high reference
frequency can be programmed in order to achieve rapid – “rough” – transient
response. This method increases the fundamental frequency by nearly the
square root of the reference frequency ratio and therefore the settling time is
reduced. When rough lock is achieved, another synchronous data transfer is
needed to switch back to the original channel spacing. A “fine” lock in will finish
the total step response. It may not be necessary to change reference frequency,
but it make sense to perform synchronous data acquisition in any case. Espe-
cially for GSM, PCN (DCS 1800) and PCS systems the synchronous mode
should be used to achieve best performance of the PMB 2347.
3. Standby Condition (power down)
Each PLL of the PMB 2347 has two programmable standby modes to reduce
the current consumption (standby 1, standby 2).
Standby 1:
The corresponding PLL is switched off, the current consumption
is reduced below 1
A.
Standby 2:
The corresponding counters, the charge pump and the outputs
are switched off. Only the preamplifier of RI-input stays active.
(See standby table)