Supertex inc.
High Voltage Protection
T/R Switch
Features
►
Up to ±100V input voltage protection
►
Low on resistance - 15Ω typical
►
Fast switching speed
►
Effectively, a simple two terminal device
►
No external supplies needed
MD0100
General Description
The Supertex MD0100 is a high voltage, two terminal, bi-
directional, current-limiting protection device. The two terminals are
interchangeable. It is designed to protect a low noise receiver from
the high voltage transmit pulses in ultrasound applications and is
commonly referred to as a T/R (transmit and receive) switch.
The MD0100 can be considered as a normally closed switch with a
typical switching resistance of 15Ω that allows small signals to pass.
Once the voltage drop across the two terminals exceeds a nominal
value of ±2.0V, the device will start to turn off. In the off state, the
MD0100 can withstand up to ±100V across its terminals. A small
amount of current, typical of 200µA, is allowed to flow through.
The applications for the MD0100 are not limited to just ultrasound. It
can also be used for resettable fuses to protect power lines, output
short circuit protection, and data acquisition. The MD0100 is available
in the SOT-89 package as a single channel device for ease of
assembly. It is also available in a 4.0x4.0mm 8-Lead DFN package as
a two channel device for high density requirements.
Applications
►
Medical ultrasound imaging
►
NDT applications
►
Fast resettable fuses
►
High side switches
►
Data acquisition
Typical Application Circuit
+90V
Transmitter
Logic
Control
and
Signal
Processing
T
X
Piezo
Transducers
-90V
R
X
Receiver
B
MD0100
T/R Switch
A
High Voltage
Switches
Doc.# DSFP-MD0100
B011513
Supertex inc.
www.supertex.com
MD0100
Ordering Information
Part Number
MD0100DK6-G
(Dual Channel)
MD0100N8-G
(Single Channel)
Package Options
8-Lead (4x4) DFN
3-Lead TO-243AA (SOT-89)
Packing
3000/Reel
2000/Reel
A1
B1
A2
B2
1
2
3
4
COM2
COM1
8
7
6
5
COM1
COM1
COM2
COM2
Pin Configuration
- G indicates package is RoHS compliant (‘Green’)
Absolute Maximum Ratings
1
Parameter
VA-B, Differential Voltage Drop
Maximum junction temperature
Storage temperature range
Power dissipation, 8-Lead DFN
2
Power dissipation, SOT-89
2
Value
0 to ±110V
+125°C
-65°C to 150°C
1.1W
1.6W
(top view)
(Pads are at bottom of device)
8-Lead DFN
COM
Notes:
1. Absolute Maximum Ratings are those values beyond which damage to the
device may occur. Functional operation under these conditions is not implied.
Continuous operation of the device at the absolute rating level may affect
device reliability. All voltages are referenced to device ground.
2. Mounted on FR4 board, 25mm x 25mm x 1.57mm
A
COM
SOT-89
B
Product Marking
0100
Typical Thermal Resistance
Package
8-Lead DFN
3-Lead TO-243AA (SOT-89)
θ
ja
44
O
C/W
133
O
C/W
YWLL
Y = Last Digit of Year Sealed
W = Code for Week Sealed
LL = Lot Number
= “Green” Packaging
8-Lead DFN
Package may or may not include the following marks: Si or
M10YW
Y = Last Digit of Year Sealed
W = Code for Week Sealed
= “Green” Packaging
SOT-89
Package may or may not include the following marks: Si or
Doc.# DSFP-MD0100
B011513
2
Supertex inc.
www.supertex.com
MD0100
Electrical Characteristics
(T
J
= 25ºC, unless otherwise specified)
Sym
BV
A-B
R
SW
V
TRIP
V
OFF
I
A-B(OFF)
I
PEAK
T
OFF
T
ON
C
SW(ON)
C
SW(OFF)
BW
T
J
Parameter
Breakdown voltage from A to B or B to A
Switch ON resistance from A to B or B to A
V
A-B
trip point to turn off
Switch turn off voltage
Switch off current
Peak switching current
Turn off time
Turn on time
Switch ON capacitance from A to B or B to A
Switch OFF capacitance from A to B or B to A
Small signal bandwidth
Operating junction temperature
Min
±100
-
-
-
-
-
-
-
-
-
-
-40
Typ
-
15
±1.0
±2.0
±200
±60
-
-
21
15
100
-
Max
-
-
±2.0
-
±300
-
20
20
-
-
-
+125
Units Conditions
V
Ω
V
V
µA
mA
ns
ns
pF
pF
MHz
°C
I
A-B
= ±500µA
I
A-B
= ±5.0mA
---
I
A-B
= ±1.0mA
V
A-B
= ±100V
See Fig. 8
See Fig. 2, 3 & 4
See Fig. 5, 6 & 7
SW = ON
V
SW
= 25V
R
LOAD
= 50Ω
---
Block Diagram
COM
Switch Control
A
B
Typical I-V Characteristics
+I
PEAK
I
A-B
I
A-B
= +200µA
-100V
-V
OFF
+1.0mA
-V
TRIP
+V
TRIP
+1.0mA
I
A-B
= -200µA
R
SW
= 15Ω
+V
OFF
V
A-B
+100V
-I
PEAK
Doc.# DSFP-MD0100
B011513
3
Supertex inc.
www.supertex.com
MD0100
Functional Description
The Supertex MD0100 can be considered as a normally
closed switch controlled by a switch control. (Refer to the
block diagram.) The switch control monitors the voltage
drop across terminals A and B. If the voltage difference is
greater than ±2.0V, the T/R switch will start to open. Once
in the open state, there is a small amount of current flowing
through the T/R switch, 200uA, to detect if the high voltage
is still present or not. The T/R switch will not close until the
voltage across terminal A and B drops within ±2.0V. A pair of
back-to-back diodes from the receive side of the switch to
ground are needed to complete the circuit and to allow the
initial peak current (about 60mA) to flow through the switch
so it can drop ±2.0V. If the diodes are not present, then there
is no current path and the voltage drop across terminal A
and B will be less than ±2.0V, so the switch will remain in the
closed position.
The other purpose of the diode is to clamp voltage spikes
to ±0.7V during transmit cycle. A low voltage diode, for ex-
ample 1.0V diode, is sufficient since it will only see ±0.7V. A
BAV99T dual diode from Diodes, Inc. was used in our test
circuit.
Figure 1: C
SW(OFF)
vs V
SW
20
19
18
17
C
SW
(pF)
16
15
14
13
12
11
10
0
10
20
30
40
50
60
70
80
90
V
SW
(V)
T
ON
and T
OFF
Time
The T
ON
and T
OFF
of the MD0100 are less than 20ns, which
provide a fast switch between the transmit mode and the
receive mode. The T
ON
and T
OFF
are input rise/fall time depen-
dent. The MD0100 turns ON and OFF faster when the rise
and fall times of the transmit pulse are faster. On the other
hand, the switch turns ON and OFF slower if the rise and fall
times of the transmit pulse are slower. The T
OFF
and T
ON
set
up are shown in Figure 2 and Figure 5 respectively.
On Resistance
When the voltage across terminals A and B is within ±2.0V,
the switch is in the receive mode, and the R
ON
is typically
15Ω. Once the voltage across terminals A and B is greater
than ±2.0V, the switch is in the transmit mode and blocks the
high voltage pulses from passing through to the receiver and
damaging it.
The MD0100 does not require any power supply. There are
only two active pins; one connects to the transmitter side
and the other one connects to the receiver side.
Figure 2: Test set up for T
OFF
500ns
+10V
Tx
0V
Transmitter
V
B
10
Switch Capacitance
The typical switch ON capacitance (C
SW(ON)
) is 21pF. This is
measured from A to B or B to A when the switch is ON.
The switch OFF capacitance is a function of the voltage
across the T/R switch. The C
SW(OFF)
is about 12 to 19 pF for
10V to 100V of the transmit voltage. Please see Figure 1 for
the C-V curve of the C
SW(OFF)
.
MD0100
V
A
Doc.# DSFP-MD0100
B011513
4
Supertex inc.
www.supertex.com
MD0100
Figure 3: T
OFF
Timing Diagram
+10V
Figure 6: T
ON
Timing Diagram
V
A
+10V
V
A
+2V
+2V
0V
V
B
10%
V
B
2V
1V
0V
Figure 4: T
OFF
at V
A
= 10V
Figure 7: T
ON
at V
A
= 10V
2V
2V
10%
1V
Figure 4 shows the actual waveform and measurement of the Figure 7 shows the actual waveform and measurement of
T
OFF
. T
OFF
is measured from 2V of the V
A
to 10% of the V
B
. the T
ON
. The T
ON
is measured from 2V of the V
A
to 1V of the
V
B
. From the above waveform, the T
ON
is 6.6ns.
From the above waveform, the T
OFF
is 11ns.
Figure 5: Test Set Up for T
ON
+10V
Figure 8: Test Set Up for I
PEAK
500ns
I
PEAK
0 - 5V
t
r
= 10ms
B
V
MD0100
A
Tx
2V
15
0V
Transmitter
V
B
MD0100
V
A
Doc.# DSFP-MD0100
B011513
5
Supertex inc.
www.supertex.com
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