NTE851
Integrated Circuit
VHF/UHF Prescaler
Description:
The NTE851 is an integrated circuit prescaler in a 14Lead DIP type package intended for use in TV
frequency synthesis tuning systems over an input frequency range of 90 to 1000MHz. It performs
division by 256 in he UHF mode and division by 64 in the VHF mode.
The mode of operation can be selected by means of the bandswitch and the separate UHF and VHF
input pins provided. The output is a complementary emittercoupled stage with controlled slew rate
for harmonic suppression.
All input pins should be AC coupled to the appropriate input signal source. Because of high sensitivity,
unbuffered coupling from the local oscillator is possible in most cases. In the UHF mode, which is
activated by applying a high level to the bandswitch input pin, all eight divider stages are operative,
resulting in division by 256. In the VHF mode, activated by a low level at the VHF input pin, two divider
stages are bypassed, resulting in division by 64. As a result, approximately the same range of output
frequencies are generated fo both the UHF and VHF TV bands. An internal amplifier/multiplexer pro-
vides this control while isolating both inputs and amplifying the VHF signal. In addition, hrmonic output
is reduced above 40MHz by limiting output signal rise and fall times and maintaining a balanced load.
Features:
D
Broadband Operation: 90 to 1000MHz
D
High Sensitivity
D
Standard 5V Power Supply
D
Dual Mode Operation: VHF/UHF
D
Complementary ECL Outputs
D
Independent VHF & UHF Input Pins
Absolute Maximum Ratings:
DC Supply Voltage
5.5V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DC bandswitch Voltage
20V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RMS Input Voltage
500mV
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Device Dissipation (T
A
+70
C)
600mW
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Derate Linearly Above 70
C
7.5mW/
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Ambient Temperature Range
0
to +70
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage Temperature Range
55
to +150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lead Temperature (During Soldering, 1/16" from case, 10sec max)
+265
C
. . . . . . . . . . . . . . . . . . . .
Electrical Characteristics: (T
A
= +25
C, V+ = 5V, V = 0 unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Supply Current
I+
Pin1 and Pin2
30
60
90
mA
UHF Bandswitch Input Voltage
V
BH
High Level
2.4
V
VHF Bandswitch Input Voltage
V
BL
Low Level
0.8
V
UHF Bandswitch Input Current
I
BH
V
BH
= 20V
0.5
mA
VHF Bandswitch Input Current
I
BL
V
BL
= 0
1
mA
UHF Sensitivity Level Input Voltage
V
IN
(U)
f
IN
= 450 to 950MHz, f
OUT
= f
IN
/256
80
mV
rms
VHF Sensitivity Level Input Voltage
V
IN
(V)
f
IN
= 90 to 275MHz, f
OUT
= f
IN
/64
mV
rms
Output Voltage
V
O
Pin4 or Pin5
0.65
1.0
V
PP
Output Voltage Rise and Fall Time
t
r
, t
f
70
ns
UHF Output
VHF Input
Output
Pin Connection Diagram
N.C.
V() 1
Output
V() 2
1
2
3
4
V(+) 1
V(+) 2
Bandswitch Input
5
6
N.C.
7
14
13
12
11
N.C.
10
9
8
VHF Input
UHF Output
.600 (15.24)
1
7
14
8
.300
(7.62)
.200 (5.08)
Max
.100 (2.45)
.099 (2.5) Min
.785 (19.95)
Max
PDF 
ZIP