Specifications
Custom Switching and the
34945A/L4445A Switch Driver
The Y1150A through Y1154A
provide very specific solutions
for connecting to a wide range
of Agilent switches and attenu-
ators. You may already have
Agilent or non-Agilent switches
and attenuators that are not
directly supported by those
distribution boards. The
Y1155A is designed to handle
all other configurations.
There are three main sections:
• Coil Drive
(Higher current Digital Output –
pulsed or continuous)
• Position Indicators
(Open collector or
TTL/CMOS Digital Input)
• LED Drive
(Low current Digital Output)
Coil Drive
Each Y1155A can drive up
to 16 coils in either Pulsed or
Continuous mode. Pulsed mode
means a 5 ms to 255 ms pulse
of the supply voltage or TTL
level is used to drive the coil.
Continuous mode channels
are just Digital Outputs. When
you close a Normally Open,
non-latching switch, you are
constantly applying the drive
signal to the switch’s relay coil.
To open the channel, the drive
signal is removed. Using 24 V
relays, the typical current drain
would be 100 mA to 300 mA
for each switch; however, 5 V
relays could draw over 500 mA.
When powered by an external
supply, a single 34945EXT
limits its overall current to 2 A.
This means you could typically
drive 5 to 10 Normally Open
24 V switches when using an
external power supply. If you
rely upon the 34945A or L4445A
to supply the 24 V to the first
34945EXT, its output current is
limited to 100 mA continuous
+ 200 mA pulsed for 15 ms,
(25% duty cycle). The 34945A/
L4445A uses storage capacitors
that permit higher current for
short duration pulses.
Current limitations are rarely,
if ever, a problem for Pulsed
mode, since only one relay at
a time is pulsed for only 15 ms
(default). Pulsed mode switches
use two coils and operate in
a latching mode. Each switch
requires a Paired Channel.
Where Continuous Mode
relays can use channels
1-8 or 11-18, Pulsed Mode
switches use two paired
channels together: Channel
1/11, 2/12, 3/13, etc. The OPEN
operation pulses the lower
channel coil, and the CLOSE
pulses the upper channel coil.
24
LED2
POS INDPWR
DRIVE
Y1155A
Coil drive
Channels
11-18
LED drive
channels
11-18
Channels
1-8
Position indicators
LED1
J104 J101
P110
P111
J106 J103
1
2
3
4
5
6
7
8
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
11
12
13
14
15
16
17
18
+VR
+VR
+VI
GND
GND
+VR
+VR
+VI
J105 J102
Y1155A
LED drive
channels
1-8, 11-18
Channels
11-18
Channels
1-8
Coil drive
Position indicators