MB15E03 Datasheet, PDF (10/22 Pages) Fujitsu Component Limited. – Single Serial Input PLL Frequency Synthesizer On-Chip 1.2 GHz Prescaler

MB15E03
When designing a synthesizer, the FC pin setting depends on the VCO and LPF characteristics.
∗: When the LPF and VCO characteristics are
similar to (1), set FC bit high.
∗: When the VCO characteristics are similar to
(2), set FC bit low.
PLL
LPF
VC
VCO
Output
Frequency
(1)
(2)
LPF Input Voltage
Power Saving Mode (Intermittent Mode Control Circuit)
Setting a PS pin to Low, the IC enters into power saving mode resultatly current sonsumption can be limited to
10µA (max.). Setting PS pin to High, power saving mode is released so that the IC works normally.
In addition, the intermittent operation control circuit is included which helps smooth start up from the power saving
mode. In general, the power consumption can be saved by the intermittent operation that powering down or waking
up the synthesizer. Such case, if the PLL is powered up uncontrolled, the resulting phase comparator output signal
is unpredictable due to an undefined phase relation between reference frequency (fr) and comparison frequency
(fp) and may in the worst case take longer time for lock up of the loop.
To prevent this, the intermittent operation control circuit enforces a limited error signal output of the phase detector
during power up, thus keeping the loop locked.
During the power saving mode, the corresponding section except for indispensable circuit for the power saving
function stops working, then current consumption is reduced to 10 µA (max.).
At that time, the Do and LD become the same state as when a loop is locking. That is, the Do becomes high
impedance.
A VCO control voltage is naturally kept at the locking voltage which defined by a LPF”s time constant. As a result
of this, VCO’s frequency is kept at the locking frequency.
Note: • While the power saving mode is executed, ZC pin should be set at ”H” or open. If ZC is set at ”L”
during power saving mode, approximately 10 µA current flows.
• PS pin must be set ”L” at Power-ON.
• The power saving mode can be released (PS : L → H) 1µs later after power supply remains stable.
• During the power saving mode, it is possible to input the serial data.
Table.8 PS Pin Setting
PS pin
Status
H
Normal mode
L
Power saving mode
10