CMOS PLL FREQUENCY SYNTHESIZER WITH POWER SAVING FUNCTION

The Fujitsu MB87093A/MB87095A/MB87096A are CMOS Phase Locked Loop (PLL) frequency synthesizers, and are suitable for mobile telephone sets or portable telephone sets. They incorporate an N-divider (10-bit counter), a reference divider (R-divider)(6-bit reference counter), a phase comparator, a charge pump, analog switches, and an intermittent mode control circuit, respectively.

A power save control input pin (PS) for the intermittent mode control circuit is used to switch between the standby and active modes. This function reduces a system's total power dissipation. On-chip analog switches enable change time constants of low-pass filters (LPF). The MB87093A/MB87095A/MB87096A have different divide ratios of R-dividers and N-dividers from each other. Other functions and characteristics are common.

FEATURES

w Single power supply voltage: VDD = 4.5 to 5.5V

w Intermittent mode control circuit

w Wide ambient temperature range: TA = -40_C to 85_C

w On-chip two analog switches

w Plastic 16-pin SSOP package (Suffix: -PFV)

w fin = (Rin / R ) x N
(1) (2) (3) (4)
(1) Output frequency of an external voltage controlled oscillator (VCO)
(2) Reference frequency
(3) Divide ratio of R-divider
(4) Divide ration of N-divider




ABSOLUTE MAXIMUM RATINGS (see Note) (VSS = 0V)





Note : Permanent device damage may occur if the above Absolute Maximum Ratings are exceeded. Functional operation should be restricted to the conditions as detailed in the operational sections data sheet. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

BLOCK DIAGRAM



PIN DESCRIPTIONS






Note: 1Refer to an intermittent operation in functional description in page 4.

FUNCTIONAL DESCRIPTIONS

1 Intermittent Operation

The intermittent operation of every MB87093A/MB87095A/MB87096A refers to the process of activating and deactivating its internal circuit for saving power dissipation. If the circuit is simply restarted from the standby state, however, an excessively large error signal might be generated, resulting in an out-of-synch lock frequency. Because the phase relationship between the reference frequency (fr) and the frequency (fv) is not stable even when they are of the same value.

To preclude this problem, every MB87093A/MB87095A/MB87096A has an intermittent mode control circuit which forces the frequencies fr and fv into the same phase other than when the MB87093A/MB87095A/MB87096A are reactivated, this minimizing the error signal and resultant lock frequency fluctuations. The intermittent mode control circuit is controlled by the PS pin. Setting the PS pin high provides the active mode, and setting the PS pin low provides the standby mode and places the MB87093A/MB87095A/ MB87096A into the standby state.

The MB87093A/MB87095A/MB87096A must be placed in the standby mode (PS = "L") when power is impressed.

2 Input sensor

The STBY pin outputs in the standby mode, and outputs high after receiving a signal via Rin pin when the mode switches from the standby mode into the active mode.

For example, it is possible to control a VCO by this function.

3 N-divider

The fvco of an external VCO output signal input through fin is divided by the N-divider and then output to the phase comparator as fv. It consists of a binary 10-bit N-counter. The divide ratio N of the N-divider for each MB87093A/MB87095A/MB87096A is shown in Table 1.

Table 1. N-divider's Divide Ratio N




4 R-divider

The R-divider divides the reference oscillation frequency (fosc) from an external reference oscillator (TCXO), and output fr to the phase comparator. It consists of a binary 6-bit R-counter. Table 2 shows the R-divider's divide ratio.

Table 2. R-divider's Divide Ratio R




5 Phase Comparator

The phase comparator detects the phase difference between the outputs fr and fv and generates an error signal that is proportional to the phase difference. The outputs from the phase comparator include 1) Do which takes one of the three states; namely, "L" (Low), "H" (high), and "Z" (high-impedance), 2) LD which indicates the PLL lock or unlock state.

5.1 Phase Comparator

The phase comparator detects the phase difference between fr and fv and generates an error signal that is proportional to the phase difference. Table 3 shows logical levels of Do and LD according to the phase relationship between fr and fv.

Table 3. Phase Comparator Inputs/Output Relationships




5.2 Phase Comparator Input/Output Waveforms

The phase comparator outputs logical levels summarized in Table 3. The pulse width of the phase comparator outputs are identical and equal to the phase difference between fr and fv as shown in Figure 1.



Figure 1. Phase Comparator Input/Output Waveforms (Charge Pump)

5.3 Lock Detector

The lock detector detects the lock and unlock states of the PLL. The lock detector outputs high when the PLL enters the lock state and outputs low when the PLL enters the unlock state as shown in Figure 2. When pulse width of the error signal is kept zero for four (4) clocks, the lock detector outputs high as a lock signal. When it detects phase difference after the PLL is locked, low is output at once. When PS is low, the lock detector outputs high compulsorily.



Figure 2. Phase Comparator Input/Output Waveforms (Lock Detector)

6 Analog Switch

The analog switch can be controlled by the CTRL pin. When the CTRL pin is high, each analog switch closes. When low, each analog switch opens. For example, a LPF's time constant can be changed by using a connect, as in Figure 3.



Figure 3. Application Example for Analog Switch

RECOMMENDED OPERATING CONDITIONS

(VSS = 0V)




ELECTRICAL CHARACTERISTICS

(VDD = 4.5 to 5.5V, VSS = 0V, TA = -40 to +85_C)







Notes:

*1: MB87093A: fin = 145 MHz, Rin = 12.8 MHz, Outputs are opened.
MB87095A: fin = 110 MHz, Rin = 12.8 MHz, Outputs are opened.
MB87096A: fin = 90 MHz, Rin = 15.36 MHz, Outputs are opened.

*2: Inputs set low. Outputs are opened.

TYPICAL APPLICATION EXAMPLE



PACKAGE DIMENSIONS







For further information please contact:

Japan

FUJITSU LIMITED
International Marketing Div.
Furukawa Sogo Bldg., 6-1, Marunouchi 2-chome
Chiyoda-ku, Tokyo 100, Japan
Tel: (03) 3216-3211
Telex: 781-22243 61
FAX: (03) 3216-0662
North and South America

FUJITSU MICROELECTRONICS, INC.
Semiconductor Division
3545 North First Street
San Jose, CA 95134-1804 USA
Tel: 408-922-9000
FAX: 408-432-9044
Europe

FUJlTSU MlKROELEKTRONIK GmbH
Am Siebenstein 6-10
63303 Dreiech-Buchschlag
Germany
Tel: (06103) 690-0
Telex: 411963 fmg d
FAX: (06103) 690-122
Asia

FUJITSU MICROELECTRONICS ASIA PTE LIMITED
51 Bras Basah Road
Plaza By The Park
#06-04 to #06-07
Singapore 0718
Tel: 336-1600
Telex: 55573
FAX: 336-1609
EFUJITSU LIMITED 1993 SD-08010-01-92-DS