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General Description
The ZX76-31-SP+ is a 507 RF digital step attenuator that offers an attenuation range up to 31 dB in 1.0 dB
steps. The control is a 5-bit serial interface. The model operates on a single +3 volt supply. See application
note AN-70-004 for 5V supply voltage. The ZX76-31-SP+ is produced using a unique case package for rug-
gedness and operation in tough environments.
Digital Step Attenuator
31 dB, 1 dB Step, 5 Bit, Serial Control Interface,
Single Supply Voltage
50Ω DC-2400 MHz
Simplified Schematic
Digital Serial Control
RF Input 16dB 8dB 4dB 2dB 1dB RF Out
REV. B
M113397
ZX76-31-SP+
EDR-7814
090423
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Product Features
• Low Insertion Loss
• High IP3, +52 dBm Typ
• Excellent return loss, 20 dB Typ
• Excellent accuracy, 0.1 dB Typ
• Single Supply Voltage: +3V
• Control inputs buffered by Schmitt Triggers
• Rigid unibody case
• Protected by US patent 6,790,049
Typical Applications
• Lab
• Instrumentation
• Test equipment
Connectors Order P/N Price Qty.
SMA ZX76-31-SP-S+ $73.95 ea. (1-9)
ZX76-31-SP+
CASE STYLE: HK1172
+ RoHS compliant in accordance
with EU Directive (2002/95/EC)
The +Suffix has been added in order to identify RoHS
Compliance. See our web site for RoHS Compliance
methodologies and qualifications.
Digital Step Attenuator ZX76-31-SP+
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RF Electrical Specifications, DC-2400 MHz, TAMB=25°C, VDD=+3V
Absolute Maximum Ratings
Parameter Ratings
Operating Temperature -40°C to 85°C
Storage Temperature -55°C to 100°C
VDD
, Supply Voltage
-0.3V Min., 4V Max.
Voltage on Control Input -0.3V Min., 6V Max.
ESD, HBM 500V
ESD, MM 100V
Input Power +24dBm
Parameter Min. Typ. Max. Units
V
DD
, Supply Voltage 2.7 3 3.3 V
I
DD
,Supply Current — — 1.5 mA
Control Input Voltage Low 0 — 0.3xV
DD
V
Control Input Voltage High 0.7xV
DD
—5VV
Control Current — — 400 MA
DC Electrical Specifications
Parameter Min. Typ. Max. Units
Switching Speed, 50% Control to 0.5dB
of Attenuation Value — 1.0 —
M
Sec
Switching Control Frequency — — 25 KHz
Switching Specifications
* IP3 and 1dB compression degrade below 1 MHz
Parameter Freq. Range
(GHz) Min. Typ. Max. Units
Accuracy @ 1 dB Attenuation Setting DC-1 — 0.02 0.1 dB
1-2.4 — 0.05 0.15 dB
Accuracy @ 2 dB Attenuation Setting DC-1 — 0.05 0.15 dB
1-2.4 — 0.15 0.25 dB
Accuracy @ 4 dB Attenuation Setting DC-1 — 0.07 0.2 dB
1-2.4 — 0.15 0.25 dB
Accuracy @ 8 dB Attenuation Setting DC-1 — 0.03 0.2 dB
1-2.4 — 0.15 0.3 dB
Accuracy @ 16 dB Attenuation Setting DC-1 — 0.1 0.3 dB
1-2.4 — 0.15 0.5 dB
Insertion Loss @ all attenuator set to 0dB DC-1 — 1.5 2.2 dB
1-2.4 — 2.0 3.0 dB
IP3 Input* (at Min. and Max. Attenuation) DC-2.4 — +52 — dBm
Input Power @ 0.2dB Compression*
(at Min. and Max. Attenuation) DC-2.4 — +24 — dBm
VSWR DC-1 — 1.2 1.5 —
1-2.4 — 1.2 1.5 —
Digital Step Attenuator ZX76-31-SP+
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Pin Description Pin Configuration
J2 J3
P2
P1
GND
+VDD
RF OUTRF IN
J2 J3
SIDE VIEW
TOP VIEW
J1-10
J1-1
J1
Cable Pin Description
Function Pin
Number Description
N/C J1-1 Not Connected
GND J1-2 Ground connection
LE J1-3 Latch Enable Input
N/C J1-4 Not Connected
GND J1-5 Ground connection
N/C J1-6 Not Connected
Clock J1-7 Serial Interface clock Input
GND J1-8 Ground connection
Data J1-9 Serial Interface data Input
N/C J1-10 Not Connected
RF in J2 RF in port (Note 1)
RF out J3 RF out port (Note 1)
GND P1 Ground connection
VDD P2 Positive Supply Voltage
Note 1: Both RF ports must be held at 0VDC or DC blocked with an external
series capacitor.
J1J4
J1-Pin
Number
J4-Pin
Number Function Description Wire Color
J1-2 J4-18 GND Ground connection BLACK
J1-3 J4-4 LE Latch Enable Input GREEN
J1-5 J4-19 GND Ground connection BLUE
J1-7 J4-2 Clock Serial Interface clock Input RED
J1-8 J4-20 GND Ground connection ORANGE
J1-9 J4-3 Data Serial Interface data Input WHITE
Note: Other pins not connected. Cable shield connected to case ground.
Digital Step Attenuator ZX76-31-SP+
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Typical Performance Curves
INSERTION LOSS (Ref)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
INSERTION LOSS (dB)
-40ºC
+25ºC
+85ºC
ATTENUATION (1 dB)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
ATTENUATION (dB)
-40°C
+25°C
+85°C
ATTENUATION (2 dB)
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
ATTENUATION (dB)
-40°C
+25°C
+85°C
ATTENUATION (4 dB)
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
ATTENUATION (dB)
-40°C
+25°C
+85°C
ATTENUATION (8 dB)
7.0
7.2
7.4
7.6
7.8
8.0
8.2
8.4
8.6
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
ATTENUATION (dB)
-40°C
+25°C
+85°C
ATTENUATION (16 dB)
14.0
14.5
15.0
15.5
16.0
16.5
17.0
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
ATTENUATION (dB)
-40°C
+25°C
+85°C
Digital Step Attenuator ZX76-31-SP+
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Typical Performance Curves
ZX76-31-SP+
RETURN LOSS IN (Ref)
0
5
10
15
20
25
30
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
RETURN LOSS (dB)
-40°C
+25°C
+85°C
RETURN LOSS OUT (Ref)
0
5
10
15
20
25
30
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
RETURN LOSS (dB)
-40°C
+25°C
+85°C
RETURN LOSS IN (Major Atten. Steps)
@ +25oC
10
20
30
40
50
60
70
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
RETURN LOSS (dB)
0 dB
1 dB
2 dB
4 dB
8 dB
16 dB
31 dB
RETURN LOSS OUT (Major Atten. Steps)
@ +25oC
10
20
30
40
50
60
70
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
RETURN LOSS (dB)
0 dB
1 dB
2 dB
4 dB
8 dB
16 dB
31 dB
ATTENUATION (31 dB)
20
22
24
26
28
30
32
34
0 500 1000 1500 2000 2500 3000 3500 4000
FREQUENCY (MHz)
ATTENUATION (dB)
-40°C
+25°C
+85°C
Digital Step Attenuator ZX76-31-SP+
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Typical Performance Curves
IP3 (Major Atten. Steps) @ +25oC
35
40
45
50
55
60
65
70
75
80
0 400 800 1200 1600 2000 2400
FREQUENCY (MHz)
IP3 (dBm)
0 dB
1 dB
2 dB
4 dB
8 dB
16 dB
31 dB
COMPRESSION @ INPUT POWER=+24dBm
(Major Atten. Steps) @ +25oC
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0 400 800 1200 1600 2000 2400
FREQUENCY (MHz)
COMPRESSION (dB)
0 dB
1 dB
2 dB
4 dB
8 dB
16 dB
31 dB
IP3 (Major Atten. Steps) @ -40oC
35
40
45
50
55
60
65
70
75
80
0 400 800 1200 1600 2000 2400
FREQUENCY (MHz)
IP3 (dBm)
0 dB
1 dB
2 dB
4 dB
8 dB
16 dB
31 dB
COMPRESSION @ INPUT POWER=+24dBm
(Major Atten. Steps) @ -40oC
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0 400 800 1200 1600 2000 2400
FREQUENCY (MHz)
COMPRESSION (dB)
0 dB
1 dB
2 dB
4 dB
8 dB
16 dB
31 dB
IP3 (Major Atten. Steps) @ +85oC
35
40
45
50
55
60
65
70
75
80
0 400 800 1200 1600 2000 2400
FREQUENCY (MHz)
IP3 (dBm)
0 dB
1 dB
2 dB
4 dB
8 dB
16 dB
31 dB
COMPRESSION @ INPUT POWER=+24dBm
(Major Atten. Steps) @ +85oC
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0 400 800 1200 1600 2000 2400
FREQUENCY (MHz)
COMPRESSION (dB)
0 dB
1 dB
2 dB
4 dB
8 dB
16 dB
31 dB
Digital Step Attenuator ZX76-31-SP+
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Outline Drawing
Recommended Mounting Hardware:
Use UNC#2 pan head screws with internal tooth lock washers for unit mounting.
Outline Dimensions ( )
inch
mm
A
BCDEFGHJKLMNPQRSWT.
GRAMS
1.20 .75 .46 1.18 .04 .17 .45 .59 .33 .21 .22 .18 1.00 .50 .35 .18 .106 35
30.5 19.1 11.6 30.0 1.0 4.3 11.4 14.9 8.3 5.3 5.6 4.6 25.4 12.7 8.9 4.6 2.69
Digital Step Attenuator ZX76-31-SP+
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Simplified Schematic
The ZX76-31-SP+ Serial interface consists of 5 control bits that select the desired attenuation state, as
shown in Table 1: Truth Table
Digital Serial Control
RF Input
16dB 8dB
4dB 2dB 1dB RF Out
LE
Clock
Data MSB LSB
tLESUP
t
SDSUP
t
SDHLD
t
LEPW
Figure 1: Serial Interface Timing Diagram
Table 2. Serial Interface AC Characteristics
Symbol Parameter Min. Max. Units
fclk
Serial data clock
frequency (Note 1) 10 MHz
tclkH Serial clock HIGH time 30 ns
tclkL Serial clock LOW time 30 ns
tLESUP
LE set-up time after last
clock falling edge 10 ns
tLEPW
LE minimum pulse
width 30 ns
tSDSUP
Serial data set-up time
before clock rising edge 10 ns
tSDHLD
Serial data hold time
after clock falling edge 10 ns
Note 1. fclk verified during the functional pattern test. Serial programming
sections of the functional pattern are clocked at 10MHz to verify fclk speci-
fication.
The serial interface is a 5-bit serial in, parallel-out shift register buffered by a transparent latch.
It is controlled by three CMOS-compatible signals: Data, Clock, and Latch Enable (LE). The Data and Clock
inputs allow data to be serially entered into the shift register, a process that is independent of the state of
the LE input.
The LE input controls the latch. When LE is HIGH, the latch is transparent and the contents of the serial shift
register control the attenuator. When LE is brought LOW, data in the shift register is latched.
The shift register should be loaded while LE is held LOW to prevent the attenuator value from changing as
data is entered. The LE input should then be toggled HIGH and brought LOW again, latching the new data.
The timing for this operation is defined by Figure 1 (Serial Interface Timing Diagram) and Table 2 (Serial
Interface AC Characteristics).
Table 1. Truth Table
Attenuation
State C16 C8 C4 C2 C1
Reference 0 0000
1 (dB) 0 0001
2 (dB) 0 0010
4 (dB) 0 0100
8 (dB) 0 1000
16 (dB) 1 0000
31 (dB) 1 1111
Note: Not all 32 possible combinations of C1 - C16 are shown in table
Control cables for programming and CD with software can be ordered separately. For details see page 10.
Digital Step Attenuator ZX76-31-SP+
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The ZX76-31-SP+, uses a common 5-bit serial word format, as shown in Table 3: 5-Bit attenuator Serial
Programming Register Map.
The first bit, the MSB, corresponds to the 16-dB Step and the B1 bit corresponds to the 1 dB step.
Table 3. 5-Bit attenuator Serial Programming Register Map
B5 B4 B3 B2 B1 B0
C16 C8 C4 C2 C1 0
MSB
(first in)
LSB
(last in)
Note: The stop bit (B0) must always be low to prevent the attenuator from entering an unknown state.
Digital Step Attenuator ZX76-31-SP+
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Recommended Accessories
Two optional cable accessories with and without interface connector are available with ZX76-31-SP+, the
ZX76-CS+ and ZX76-WS+.
ZX76-CS+ shielded cable with interface 25 pin D-type connector J4 and supplied software are used to control
the ZX76-31-SP+ digital attenuator from a computer, using LPT port.
ZX76-WS+ shielded cable without interface 25 pin D-type connector enables customer to use the ZX76-31-SP+
digital attenuator in his own application. Cable length is 4.9 feet / 1.5 meters.
Note: Mini-Circuits can supply control cables with other options for the J4 connector and/or different cable lengths.
Consult factory with your specific requirements.
ZX76-CS+ Control Cable
ZX76-CS+ wiring information
J1 J4
J1-Pin
Number
J4-Pin
Number Function Description Wire Color
J1-2 J4-18 GND Ground connection BLACK
J1-3 J4-4 LE Latch Enable Input GREEN
J1-5 J4-19 GND Ground connection BLUE
J1-7 J4-2 Clock Serial Interface clock Input RED
J1-8 J4-20 GND Ground connection ORANGE
J1-9 J4-3 Data Serial Interface data Input WHITE
Note: Other pins not connected. Cable shield connected to case ground.
Digital Step Attenuator ZX76-31-SP+
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Ordering Information
J1-Pin
Number Function Description Wire Color
J1-2 GND Ground connection BLACK
J1-3 LE Latch Enable Input GREEN
J1-5 GND Ground connection BLUE
J1-7 Clock Serial Interface clock Input RED
J1-8 GND Ground connection ORANGE
J1-9 Data Serial Interface data Input WHITE
ZX76-WS+ wiring information
Model Number Description
Quantity
Min.
No. of Units
Price
$
Ea.
ZX76-31-SP-S+ Digital attenuator - Serial interface
Single Positive Supply Voltage 1-9 73.95
ZX76-CS+ Cable accessory with interface connector 1 22.95
ZX76-WS+ Cable accessory without interface connector 1 15.95
ZX76-CD* CD ROM ZX76 programming software 1 No Charge
*Note: To receive the CD, request when placing order.
J1
ZX76-WS+ Control Cable
Note: Other pins not connected. Cable shield connected to case ground.
