IM-275
INSTALLATION & OPERATING
INSTRUCTIONS
Models 150T, 151T, & 152T
SmartStep
®
Programmable Attenuators
This documentation may not be reproduced in any form, for any
purpose unless authorized in writing by Aeroflex / Weinschel, Inc.
©
Aeroflex / Weinschel, Inc.
Frederick, Maryland
1997 - 2010
REV. 3-10
IM-275
GENERAL
This manual provides general installation instructions and
wiring data to be used as an aid in installing the Aeroflex /
Weinschel Model 150T, 151T and 152T Series SmartStep
Programmable Attenuators into any subsystem or applica-
tion. Also included are specifications and other technical
data to help in the installation and operation of your 150T Series
Programmable Attenuator.
Each attenuator consists of a cascaded assembly of switched attenuator cells
(Figure 1) and a internal TTL interface. The attenuator elements located in the
attenuator cell are created by a thin-film process which provides exceptional long-
term stability, low power and temperature coefficients. This series of step
attenuators uses a reed switching structure that provides rapid switching togeth-
er with low insertion loss.
Figure 1. SmartStep Driver Circuitry
2
150 T Series SmartStep
®
Programmable Attenuators
BUILT-IN SMARTSTEP DRIVER CIRCUITRY:
These SmartStep
®
attenuators feature an
internal microcontroller-based driver that provides a TTL-level digital interface for control of
the attenuator relays. This card simplifies operation and interfacing requirements, while at
the same time providing for greatly enhanced flexibility over past designs. User-selectable
modes of operation include both parallel and serial Smartstep bus. The parallel mode pro-
vides a simple, one-bit per relay on/off control with internal pullups for use primarily in
single attenuator applications. This mode allows the attenuator to be controlled via a vari-
ety of methods, such as a TTL-level digital output port, or mechanical toggle switches. The
Smartstep mode provides a two-wire serial bus structure and protocol for connecting a
number of devices to a single host control interface, suitable for use in larger system and
sub-system applications.
The SmartStep contains non-volatile configuration memory that is used to hold a wide vari-
ety of attenuator and driver-dependant parameters, including serial number, attenuator cell
dB values, relay configurations, and switching requirements, which are all accessable via
the Smartstep interface. This frees the system designer from such low-level details, allow-
ing faster integration. In either operational mode, the microcontroller enters an idle
condition during periods of inactivity, turning off all on-board clocks, reducing EMI con-
cerns, and lowering power consumption. On-board regulation for the digital circuitry allows
the SmartStep to operate from a single input supply voltage.
CELL CONFIGURATION
The table below list all the standard attenuation ranges and cell configurations for
Aeroflex / Weinschel 150T Series Smartstep Programmable Attenuators (Models
150T, 151T, 152T). Note the dash number is the attenuation value of your atten-
uator.
Cell
No.
4
4
5
4
5
3
4
4
4
4
Range/
Step Size
D7
15XT-11
15XT-15
15XT-31
15XT-55
15XT-62
15XT-70*
152T-70
15XT-75
15XT-90
15XT-110
0-11/1
0-15/1
0-31/1
0-55/5
0-62/2
0-70/10
0-70/10
0-75/5
0-90/10
0-110/10
20
10
30
40
8
4
D6
Data Bit-Cell Value (dB)
D5
D4
D3
4
4
16
20
16
D2
2
2
2
20
4
20
20
20
20
20
D1
4
8
8
10
32
40
20
40
30
40
D0
1
1
1
5
2
10
10
5
10
10
Model No.
* Model 152AT-70 also!
3
IM-275
INSTALLATION
MOUNTING:
Each Programmable Step Attenuator is supplied with two mounting
screws (P/N MS35335-57). These screws will fit any of the mounting holes (4-40
UNC-2B x 0.22 MIN DP) located on either side of the attenuator.
RF CABLE INSTALLATION:
Care should be taken to prevent strain on the inter-
connecting cables, since damage here may not always be apparent. Check the
attaching RF cables and the SMA connectors for signs of cracked insulation
and/or bent or worn pins prior to connection. Tests show that connectors must be
clean for accuracy and stability. This requires an inspection and cleaning of each
connector immediately before use. When cleaning precautions are observed reg-
ularly, connectors can maintain their stability for over several thousand
connection cycles. Weinschel recommends a torque value of 7 to 10 inch pounds
when connecting any RF cable to the attenuator's RF connectors.
DEVICE INTERFACE BUS (DIB) CONNECTOR WIRING:
Figure 2 shows the
connectors contact pin numbering scheme and the signal designator for signal
present at each contact pin.
Name
Pin
1
2
3,4
7
8
5
6
11
12
9
10
13
Description
dc Supply Voltage, +12 to 15 V (1)
dc Supply Voltage, +12 to 15 V (1)
dc Return
Data Bit 0 (lsb)/I2C SDA
Data Bit 1//I2C SCL
Data Bit 2
Data Bit 3
Data Bit 4
Data Bit 5
Data Bit 6
Data Bit 7 (msb)
Parallel/Serial Mode Select
1=Parallel
0=I2C
This pin has a 22K resistive pull-up to 5 V.
Leave unconnected for parallel mode operation.
Reset Input, low active
This pin has a 22K resistive pull-up to 5 V
Leave unconnected if not used.
PIN 14
PIN 13
VIN
VIN
GND
D0/SDA
D1/SCL
D2
D3
D4
D5
D6
D7
Mode
Select
/RST
14
PIN 2
PIN 1
Note: D0-D7 pins contain weak active pullups, capable of sourcing
approximately 150 mA.
(1) Voltage may be applied to either PIN 1 or 2 or both.
Figure 2. DIB Connector Wiring
4
150 T Series SmartStep
®
Programmable Attenuators
PARALLEL MODE OPERATION:
In the parallel mode of operation, the Smartstep attenuator accepts TTL-level
parallel data on the D0-D7 input data lines. Each data line controls a separate
attenuation cell, where a logic 1 input (TTL high) engages the attenuation cell, and
a logic 0 input (TTL low) bypasses the cell, providing a through path. The data
lines have a weak active pull-up to +5V, and therefore if the pin is left unconnect-
ed (or floating), will engage the attenuation cell. The on-board microcontroller
debounces the data lines and generates the proper timing and control sequence
for operation of the relays. The data line inputs are not latched, and must be driv-
en with a constant level to keep the desired attenuation setting.
SERIAL MODE OPERATION:
In the serial mode of operation, the Smartstep attenuator communicates over a
two-wire serial bus to the Aeroflex / Weinschel Model 8210A Smartstep Interface.
The bus uses a clock (SCL) and data (SDA) line to send and receive program-
ming and configuration information. The messages sent over the bus use the
software protocol as defined in the ACCESS.bus™ V2.2 specification (Base
Protocol) with Weinschel-specific extensions to support the control of step atten-
uators (StepAttn Protocol). These protocols and operating instructions can be
located in the Model 8210A instruction manual (IM-288). The ACCESS.bus™
messages have the following format:
Byte#
1
2
3
4
Length+4
D7
D7
S7
P
X7
D6
D6
S6
L6
X6
D5
D5
S5
L5
X5
D4
D4
S4
L4
X4
D3
D3
S3
L3
X3
D2
D2
S2
L2
X2
D1
D1
S1
L1
X1
D0
0
0
L0
X0
Description
Destination address
Source address
Protocol flag & Msg Length
msg body- 0 to 127 bytes
Checksum
For an indepth discussion of the hardware and software operation, refer to the
ACCESS.bus™ specification.
5
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