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The NJ88C51 is a low power integrated circuit, designed as the heart of a fast locking PLL subsystem in a mobile radio application. It is manufactured on GEC Plessey Semiconductors 1.4 micron double polysilicon CMOS process, which ensures that low power and low noise performance is achieved.
The device contains two synthesisers, one for the generation of VHF signals up to 125MHz and a second for UHF (when used with a mulitmodulus prescaler such as the SP8713/14/15). The main synthesiser has the capability of driving a dual speed loop filter and also can perform Fractional-N interpolation.
Both synthesisers use current source outputs from their phase detectors to minimise external components. Various sections may be powered down for battery economy.
- 30MHz main synthesiser
- 125MHz auxiliary synthesiser
- Programmable output current from phase detector - up to 10mA
- High input sensitivity
- Fractional-N interpolator
- Supports up to 4 modulus prescalers
- SSOP package
- Lock Detect Output
- Low noise modulus control outputs

- NMT, AMPS, ETACS cellular
- GSM, IS-54, RCR-27 cellular
- DCS1800 microcellular
- DECT, PHP cordless telephones

1DATASerial input for programming data.
2STROBEProgram enable pin, active low.
3FIMMain synthesiser balanced input buffer, may be used with single ended prescaler output if Fimb is biased.
4FIMBMain synthesiser balanced input buffer, may be used with balanced prescaler output, or biased for single ended operation.
5AGNDAnalogue ground supply pin.
6RIMaster reference frequency input, should be a.c coupled from an accurate source.
7AVDDAnalogue supply pin (nominally 5V).
8FIAAuxiliary synthesiser frequency input, should be a.c coupled.
9RSACurrent setting resistor connection defining auxiliary phase detector output current.
10PDATristate current output from auxiliary phase detector.
11PDITristate current output from the main synthesiser's phase detector giving integral control.
12GNDDigital ground supply pin.
13PDPTristate current output from the main synthesiser's phase detector giving proportional control.
14VDDDigital supply pin (nominally 5V).
15RSMCurrent setting resistor connection defining main synthesiser's phase detector output currents.
16RSCCurrent setting resistor connection defining the compensation current for fractional-N ripple elimination in the main synthesiser's current source outputs.
17LDLock Detect OutputLock Detect Output
18MOD1Modulus control pin.
19MOD2Modulus control pin.
20CKINSerial clock input for programming bus.

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