MAX4708ESE Maxim Integrated Products, MAX4708ESE Datasheet - Page 10

• Manufacturer Part Number: MAX4708ESE
• Description: Multiplexer Switch ICs
• Manufacturer: Maxim Integrated Products
• Type: Analog Multiplexerr

Specifications of MAX4708ESE

• Number Of Channels: 1 Channel
• On Resistance (max): 950 Ohms at 12 V
• Propagation Delay Time: 350 ns at +/- 15 V, 400 ns at 12 V
• On Time (max): 500 ns at 12 V
• Off Time (max): 250 ns at 12 V
• Supply Voltage (max): 36 V
• Supply Voltage (min): 9 V
• Maximum Power Dissipation: 696 mW
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Package / Case: SOIC-16 Narrow
• Mounting Style: SMD/SMT
• Switch Current (typ): 0.37 mA at 15 V, - 0.2 mA at - 15 V
• Lead Free Status / Rohs Status: No

Fault-Protected, Single 8-to-1/
Dual 4-to-1 Multiplexers
Several unique features differentiate the MAX4708/
MAX4709 from traditional fault-protected multiplexers.
First, instead of the three series FETs utilized in older
designs, the MAX4708/MAX4709 design employs two
parallel FETs for lower on-resistance and improved flat-
ness. Second, older devices limited the range of signal
amplitudes the switch could pass by as much as 3V
below the supply rails. The MAX4708/MAX4709 feature
rail-to-rail signal handling that allows the devices to
transmit signals with amplitudes at or slightly beyond
the supply rails. Finally, in former designs (MAX4508/
MAX4509), when a fault occurred, the devices clamped
and held the output voltage at the appropriate supply
rail until the fault was removed. Instead, the
MAX4708/MAX4709 now disconnect COM_ from NO_
during a fault condition, making COM_ a high-imped-
ance output as long as the fault is present. Operation is
identical for both positive and negative fault polarities.
When the NO_ voltage ranges beyond supply rails
(fault condition), the NO_ input becomes high imped-
ance, regardless of the switch state or load resistance.
If power is removed, and the fault voltage is still pre-
sent, the NO_ terminals remain high impedance. The
fault voltage can be up to ±40V, with V+ = V- = 0.
The COM_ pins are not fault protected. Limit any volt-
age sources connected to COM_ to the supply rails.
Figure 1 shows the internal construction of a single nor-
mally open (NO) switch, with the analog signal paths
shown in bold. The parallel combination of N-channel
FET N1 and P-channel FET P1 form the analog switch.
During normal operation, these FETs are driven on and
off simultaneously according to the control voltages on
A_. During a fault condition, both FETs turn off.
The maximum allowable input voltage for safe operation
depends on whether supplies are on or off, and the load
configuration on COM_. If COM_ is referred to a voltage
other than ground, but within the supplies, V
range higher or lower than the supplies, provided the
absolute value of |V
For example, with V+ = V- = 0, if the load is referred to
+10V at COM_, then the NO_ voltage range can be from
+50V to -30V. If the supplies are ±15V and COM_ is refer-
enced to ground through a load, the maximum NO_ volt-
age is ±36V. If the supplies are off and the COM output is
referenced to ground, the maximum NO_ voltage is ±40V.
Two comparators continuously compare the voltage on
NO_ with V+ and V- supply voltages. When the signal
10
______________________________________________________________________________________
NO_
Detailed Description
- V
COM_
| is less than 40V.
NO_ Input Voltage
Normal Operation
NO_
can
on NO_ ranges between V+ and V-, the multiplexer
operates normally, with FETs N1 and P1 turning on and
off in response to the control signals on A_ (Figure 1).
When the switch state is on, the parallel combination of
N1 and P1 forms a low-value resistor between NO_ and
COM_ so that signals pass equally well in either direc-
tion. When the switch state is off, both NO_ and COM_
are high-impedance inputs.
A fault condition occurs when the voltage at any NO_
input exceeds the supply rail. At this point, the output of
one of the two fault comparators goes high, effectively
turning OFF both FETs N1 and P1. With the two FETs in
the OFF position, both the switch input (NO_) and the out-
put (COM_) go into a high-impedance state. They remain
high impedance regardless of the state of the control volt-
ages in A_ and EN, until the fault is removed. The input
voltage must not exceed the absolute maximum rating at
any moment (see the Absolute Maximum Ratings section).
A fault condition on the selected channel drives COM_
to a high-impedance state. However, the fault condition
does not affect the performance of other channels.
Therefore, while the selected channel is in fault condi-
tion, selecting another channel or operating under nor-
mal condition, drives COM_ out of high impedance.
When a fast rising or falling transient on NO_ exceeds
V+ or V-, there is a 100ns delay before the fault protec-
tion turns on (see the Typical Operating Charac-
teristics , Fault Response Time). COM_ follows NO_
until the fault protection turns on. This delay is due to
the switch on-resistance and circuit capacitance to
ground. When the input transient returns to within the
supply rails, there is a longer output recovery time (see
the Typical Operating Characteristics , Fault Response
Times). These values depend on the COM_ output
resistance and capacitance. Higher COM_ output resis-
tance and capacitance increase the recovery times.
The delays do not depend on the fault amplitude.
The GND, COM_, and A_ pins are not fault protected.
ESD-protection diodes internally connect A_ to both V+
and V-. If a signal on GND, COM_, or A_ exceeds V+ or
V- by more than 300mV, excessive current can flow to
or from the supplies, possibly damaging the device.
The logic-level thresholds are CMOS and TTL compatible
with V+ = +15V and V- = -15V. Logic levels change as V+
increases (see the Typical Operating Characteristics ,
Logic-Level Threshold Voltage vs. Supply Voltage.)
Transient Fault Condition
Logic-Level Thresholds
Fault Conditions
COM and A_