DG411F Datasheet, PDF (9/16 Pages) Maxim Integrated Products – Quad, Rail-to-Rail, Fault-Protected, SPST Analog Switches

Quad, Rail-to-Rail, Fault-Protected,
SPST Analog Switches
Pin Description
DG411F
1, 16, 9, 8
2, 15, 10, 7
3, 14, 11, 6
—
—
—
4
5
12
13
PIN
DG412F
1, 16, 9, 8
2, 15, 10, 7
—
3, 14, 11, 6
—
—
4
5
12
13
DG413F
1, 16, 9, 8
2, 15, 10, 7
—
—
3, 6
14, 11
4
5
12
13
NAME
FUNCTION
IN1, IN2, IN3, IN4 Logic Control Digital Inputs
COM1, COM2, COM3,
COM4
Analog Switch Common Terminals
NC1, NC2, NC3, NC4 Analog Switch Normally Closed Terminals
NO1, NO2, NO3, NO4 Analog Switch Normally Open Terminals
NO1, NO4
Analog Switch Normally Open Terminals
NC2, NC3
Analog Switch Normally Closed Terminals
V-
Negative-Supply Voltage Input. Connect to GND for single-
supply operation. Bypass with a 0.1µF capacitor to GND.
GND
Ground. Connect to digital ground.
N.C.
No Connection. Not internally connected.
V+
Positive-Supply Voltage Input. Bypass with a 0.1µF capacitor
to GND.
Detailed Description
The DG411F/DG412F/DG413F are fault-protected
CMOS analog switches with unique operation and
construction. These switches differ considerably from
traditional fault-protection switches, with several advan-
tages. First, they are constructed with two parallel
FETs, allowing very low on-resistance when the switch
is on. Second, they allow signals on the NO_ or NC_
pins that are within, or slightly beyond, the supply rails
to be passed through the switch to the COM_ terminal
(or vice versa), allowing true rail-to-rail signal operation.
Third, the DG411F/DG412F/DG413F have the same
fault-protection performance on any of the NO_, NC_,
or COM_ switch inputs. Operation is identical for both
fault polarities. The fault protection extends to ±36V
from GND with ±15V supplies.
During a fault condition, the particular overvoltage input
(COM_, NO_, NC_) pin becomes high impedance
regardless of the switch state or load resistance. When
power is removed, the fault protection is still in effect. In
this case, the COM_, NO_, or NC_ terminals are a virtu-
al open circuit. The fault can be up to ±40V with power
off. The switches turn off when V+ is not powered,
regardless of V-.
Pin Compatibility
These switches have identical pinouts to common non-
fault-protected CMOS switches. They allow for carefree
direct replacement in existing printed circuit boards
since the NO_, NC_, and COM_ pins of each switch are
fault protected.
Internal Construction
Internal construction is shown in Figure 1, with the ana-
log signal paths shown in bold. A single NO switch is
shown. The NC configuration is identical except the
logic-level translator becomes an inverter. The analog
switch is formed by the parallel combination of N-chan-
nel FET (N1) and P-channel FET (P1), which are driven
on and off simultaneously according to the input fault
condition and the logic-level state.
Normal Operation
Two comparators continuously compare the voltage on
the COM_, NO_, and NC_ pins with V+ and V-. When
the signal on COM_, NO_, or NC_ is between V+ and
V-, the switch acts normally, with FETs N1 and P1 turn-
ing on and off in response to IN_ signals. The parallel
combination of N1 and P1 forms a low-value resistor
between NO_ (or NC_) and COM_ so that signals pass
equally well in either direction.
Positive Fault Condition
When the signal on NO_ (or NC_) and COM_ exceeds
V+ by about 50mV, the high-fault comparator output is
high, turning off FETs N1 and P1. This makes the NO_
(or NC_) and COM_ pins high impedance regardless of
_______________________________________________________________________________________ 9