7-bit programmable ‘A’ counter and the necessary control and
latch circuitry for accepting and latching the input data.
Data is presented as eight 4-bit words under external control
from a suitable microprocessor..
It is intended to be used in conjunction with a two-modulus
prescaler such as the SP8710 series to produce a universal
binary coded synthesiser.
The NJ8821 is available in Plastic DIL (DP) and Miniature
Plastic DIL (MP) packages, both with operating temperature
range of
230°C
to
170°C.
The NJ8821MA is available only in
Ceramic DIL package with operating temperature range of
240°C
to
185°C.
PDA
PDB
LD
F
IN
V
SS
V
DD
OSC IN
OSC OUT
D0
D1
1
2
3
4
5
20
19
18
17
16
CH
RB
MC
DS2
DS1
DS0
PE
NC
D3
D2
NJ8821
6
7
8
9
10
15
14
13
12
11
DP20, MP20
DG20
FEATURES
Fig.1 Pin connections - top view
s
s
s
s
Low Power Consumption
Microprocessor Compatible
High Performance Sample and Hold Phase Detector
>10MHz Input Frequency
ABSOLUTE MAXIMUM RATINGS
Supply voltage, V
DD
2V
SS
Input voltage
Open drain output, pin 3
All other pins
Storage temperature
Storage temperature
20·5V
to 7V
7V
V
SS
20·3V
to V
DD
10·3V
265°C
to
1150°C
(DG package, NJ8821MA)
255°C
to
1125°C
(DP and MP packages, NJ8821)
ORDERING INFORMATION
NJ8821 BA DP
Plastic DIL Package
NJ8821 BA MP
Miniature Plastic DIL Package
NJ8821 MA DG
Ceramic DIL Package
DATA SELECT INPUTS
DS0 DS1 DS2
15
PROGRAM
ENABLE (PE)
14
LATCH SELECT
LOGIC
16
17
TO
INTERNAL
LATCHES
f
r
RB
19
CH
20
OSC IN
OSC OUT
7
8
REFERENCE COUNTER
(11BITS)
42
SAMPLE/HOLD
PHASE
DETECTOR
FREQUENCY/
PHASE
DETECTOR
1
PDA
LATCH 6 LATCH 7 LATCH 8
2
D0
DATA
D1
INPUTS
D2
D3
9
10
11
12
PDB
3
V
SS
LOCK DETECT (LD)
LATCH 4 LATCH 5
LATCH 1 LATCH 2 LATCH 3
F
IN
4
‘A’ COUNTER
(7 BITS)
‘M’ COUNTER
(10 BITS)
f
v
V
DD
V
SS
6
CONTROL LOGIC
5
18
MODULUS
CONTROL
OUTPUT (MC)
Fig.2 Block diagram
NJ8821
ELECTRICAL CHARACTERISTICS AT V
DD
= 5V
Test conditions unless otherwise stated:
V
DD
–V
SS
=5V
±0·5V.
Temperature range NJ8821 BA: –30°C to +70°C; NJ8821MA: –40°C to +85°C
DC Characteristics
Characteristic
Min.
Supply current
OUTPUT LEVELS
Modulus Control Output (MC)
High level
Low level
Lock Detect Output (LD)
Low level
Open drain pull-up voltage
PDB Output
High level
Low level
3-state leakage current
INPUT LEVELS
Data Inputs (D0-D3)
High level
Low level
Program Enable Input (PE)
High level
Low level
Data Select Inputs (DS0-DS2)
High level
Low level
AC Characteristics
Characteristic
Min.
F
IN
and OSC IN input level
Max. operating frequency, f
F
IN
and f
osc
Propagation delay, clock to MC
Strobe pulse width, t
W(ST)
Data set-up time, t
DS
Data hold time, t
DH
Latch address set-up time, t
SE
Latch address hold time, t
HE
Digital phase detector propagation delay
Gain programming resistor, RB
Hold capacitor, CH
Output resistance, PDA
Digital phase detector gain
200
10·6
30
2
1
1
1
1
500
5
1
5
0·4
50
Value
Typ.
Max.
Units
Conditions
Value
Typ.
3·5
0·7
Max.
5·5
1·5
mA
mA
Units
Conditions
f
osc
, f
F
IN
= 10MHz
f
osc
, f
F
IN
= 1·0MHz
0 to 5V
square
wave
4·6
0·4
0·4
7
4·6
0·4
±0·1
V
V
V
V
V
V
µA
I
SOURCE
= 1mA
I
SINK
= 1mA
I
SINK
= 4mA
I
SOURCE
= 5mA
I
SINK
= 5mA
4·25
0·4
4·25
0·75
4·25
0·75
V
V
V
V
V
V
TTL compatible
See note 1
mVRMS 10MHz AC-coupled sinewave
MHz
Input squarewave V
DD
to V
SS
,
See note 4.
ns
See note 2.
µs
µs
See Fig. 6
µs
µs
µs
ns
See note 3.
kΩ
nF
kΩ
V/Rad
NOTES
1. Data inputs have internal pull-up resistors to enable them to be driven from TTL outputs.
2. All counters have outputs directly synchronous with their respective clock rising edges.
3. The finite output resistance of the internal voltage follower and ‘on’ resistance of the sample switch driving this pin will add a finite time constant
to the loop. An external 1nF hold capacitor will give a maximum time constant of 5µs, typically.
4. Operation at up to 15MHz is possible with a full logic swing but is not guaranteed.
2
NJ8821
PIN DESCRIPTIONS
Pin no.
1
Name
PDA
Description
Analog output from the sample and hold phase comparator for use as a ‘fine’ error signal. Output at
(V
DD
2V
SS
)/2 when the system is in lock. Voltage increases as f
v
phase lead increases; voltage
decreases as f
r
phase lead increases. Output is linear over only a narrow phase window, determined
by gain (programmed by RB).
Three-state output from the phase/frequency detector for use as a ‘coarse’ error signal.
f
v
.
f
r
or f
v
leading: positive pulses with respect to the bias point V
BIAS
f
v
,
f
r
or f
r
leading: negative pulses with respect to the bias point V
BIAS
f
v
= f
r
and phase error within PDA window: high impedance.
An open-drain lock detect output at low level when phase error is within PDA window (in lock); high
impedance at all other times.
The input to the main counters, normally driven from a prescaler, which may be AC-coupled or, when
a full logic swing is available, may be DC-coupled.
Negative supply (ground).
Positive supply.
2
PDB
3
4
5
6
7, 8
LD
F
IN
V
SS
V
DD
OSC IN/ These pins form an on-chip reference oscillator when a series resonant crystal is connected across
OSC OUT them. Capacitors of appropriate value are also required between each end of the crystal and ground
to provide the necessary additional phase shift. An external reference signal may, alternatively, be
applied to OSC IN. This may be a low-level signal, AC-coupled, or if a full logic swing is available it may
be DC-coupled. The program range of the reference counter is 3 to 2047, with the division ratio being
twice the programmed number.
D0-D3
NC
PE
DS0-DS2
MC
Data on these inputs is transferred to the internal data latches during the appropriate data read time
slot. D3 is MSB, D0 is LSB.
No connection
This pin is used as a strobe for the data. A logic ‘1’ on this pin transfers data from the D0-D3 pins to
the internal latch addressed by the data select (DS0-DS2) pins . A logic ‘0’ disables the data inputs.
Data select inputs for addressing the internal data latches
Modulus control output for controlling an external dual-modulus prescaler. MC will be low at the beginning
of a count cycle and will remain low until the ‘A’ counter completes its cycle. MC then goes high and
remains high until the ‘M’ counter completes its cycle, at which point both ‘A’ and ‘M’ counters are reset.
This gives a total division ratio of
MP
1
A,
where
P
and
P
11
represent the dual-modulus prescaler
values. The program range of the ‘A’ counter is 0-127 and therefore can control prescalers with a
division ratio up to and including
4128/129.
The programming range of the ‘M’ counter is 8-1023
and, for correct operation,
M
>
A.
Where every possible channel is required, the minimum total division
ratio should be
P
2
2
P.
An external sample and hold phase comparator gain programming resistor should be connected
between this pin and V
SS
.
An external hold capacitor should be connected between this pin and V
SS
.
8
V
DD
= 5V
OSC IN, F
IN
= 0V TO 5V SQUARE WAVE
7
SUPPLY CURRENT (mA)
6
5
10MHz
4
1MHz
3
2
TOTAL SUPPLY CURRENT IS
THE SUM OF THAT DUE TO F
IN
AND OSC IN
1
2
3
4
5
6
7
INPUT FREQUENCY (MHz)
8
9
10
1
V
DD
= 5V
F
IN
= LOW FREQUENCY
0V TO 5V SQUARE WAVE
9,10, 11, 12
13
14
15, 16, 17
18
19
20
2·0
RB
CH
SUPPLY CURRENT (mA)
1·5
OSC IN
1·0
F
IN
0·5
0·2
0·4
0·6
0·8
1·0
1·2
INPUT LEVEL (V RMS)
1·4
1·6
Fig. 3 Typical supply current v. input frequency
Fig. 4 Typical supply current v. input level, OSC IN
3
NJ8821
PROGRAMMING
Timing is generated externally, normally from a
microprocessor, and allows the user to change the data in
selected latches as defined by the data map Fig.5. The PE pin
is used as a strobe for the data: taking PE high causes data to
be transferred from the data pins (D0-D3) into the addressed
latch. Following the falling edge of PE, the data is retained in
the addressed latch and the data inputs are disabled. Data
transfer from all internal latches into the counters occurs
simultaneously with the transfer of data into latch 1, which
would therefore normally be the last latch addressed during
each channel change. Timing information for this mode of
operation is given in Fig. 6.
When re-programming, a reset to zero state is followed by
reloading with the new counter values. This means that the
synthesiser loop lock-up time is well defined and less than
10ms. If shorter lock-up times are are required when making
only small changes in frequency, the GPS NJ8823 (with non-
resettable counters) should be considered.
WORD DS2
1
2
3
4
5
6
7
8
0
0
0
0
1
1
1
1
DS1
0
0
1
1
0
0
1
1
DS0
0
1
0
1
0
1
0
1
D3
M1
M5
M9
A3
-
R3
R7
-
D2
M0
M4
M8
A2
A6
R2
R6
R10
D1
-
M3
M7
A1
A5
R1
R5
R9
D0
-
M2
M6
A0
A4
R0
R4
R8
Fig. 5 Data map
DS0-DS2
PE
D0 - D3
t
DS
t
SE
t
W(ST)
t
DH
t
HE
Fig. 6 Timing diagram
PHASE COMPARATORS
The digital phase/frequency detector drives a three-state
output, PDB, which provides a ‘coarse’ error signal to enable
fast switching between channels. The PDB output is active
until the phase error is within the sample and hold phase
detector, PDA, window, when PDB becomes high impedance.
Phase-lock is indicated at this point by a low level on LD. The
sample and hold phase detector provides a ‘fine’ error signal
to give further phase adjustment and to hold the loop in lock.
An internally generated ramp, controlled by the digital
output from both the reference and main divider chains, is
sampled at the reference frequency to give the ‘fine’ error
signal, PDA. When in phase lock, this output would be typically
at (V
DD
2V
SS
)/2 and any offset from this would be proportional
to phase error. The relationship between this offset and the
phase error is the phase comparator gain, which is
programmable with an external resistor, RB. An internal 50pF
capacitor is used in the sample and hold comparator.
CRYSTAL OSCILLATOR
When using the internal oscillator, the stability may be
enhanced at high frequencies by the inclusion of a resistor
between pin 8 (OSC OUT) and the other components. A value
of 150-270Ω is advised.
PROGRAMMING/POWER UP
Data and signal input pins should not have input applied to
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as a representation relating to the products or services concerned. No warranty or guarantee express or implied is made regarding the capability, performance or suitability of any product or service. The Company
reserves the right to alter without prior knowledge the specification, design or price of any product or service. Information concerning possible methods of use is provided as a guide only and does not constitute
any guarantee that such methods of use will be satisfactory in a specific piece of equipment. It is the user's responsibility to fully determine the performance and suitability of any equipment using such information
and to ensure that any publication or data used is up to date and has not been superseded. These products are not suitable for use in any medical products whose failure to perform may result in significant injury
or death to the user. All products and materials are sold and services provided subject to the Company's conditions of sale, which are available on request.
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