MAX11044 Datasheet, PDF (11/19 Pages) Maxim Integrated Products – 4-/6-/8-Channel, 16-Bit, Simultaneous-Sampling ADCs

4-/6-/8-Channel, 16-Bit,
Simultaneous-Sampling ADCs
To make use of the input clamps (see Figure 1), con-
nect a resistor (R_S) between the analog input and the
voltage source to limit the voltage at the analog input so
that the fault current into the MAX11044/MAX11045/
MAX11046 does not exceed ±20mA. Note that the volt-
age at the analog input pin limits to approximately 7V
during a fault condition so the following equation can
be used to calculate the value of R_S:
R_S
=
V_{FAULT _ MAX}
20mA
- 7V
where V_{FAULT_MAX} is the maximum voltage that the
source produces during a fault condition.
Figures 2 and 3 illustrate the clamp circuit voltage-cur-
rent characteristics for a source impedance R_S =
1280Ω. While the input voltage is within the ±(V_AVDD +
300mV) range, no current flows in the input clamps.
Once the input voltage goes beyond this voltage range,
the clamps turn on and limit the voltage at the input pin.
INPUT
PIN
SIGNAL VOLTAGE
AVDD
R_S
CH0
SOURCE
CLAMP
S/H
16-BIT ADC
CH7
CLAMP
S/H
16-BIT ADC
AGNDS
AGND
MAX11044
MAX11045
MAX11046
REFIO
BANDGAP
REFERENCE
INT REF
REF
BUF
EXT REF
DVDD
DB15
DB4
DB3
DB0
CONFIGURATION
REGISTERS
INTERFACE
AND
CONTROL
WR
RD
CS
CONVST
SHDN
EOC
RDC
DGND
Figure 1. Required Setup for Clamp Circuit
30
R_S = 1280Ω
20 ^{VAVDD = 5V}
AT CH_ INPUT
10
0
AT SOURCE
30
R_S = 1280Ω
20 ^{VAVDD = 5V}
10
AT SOURCE
0
AT CH_ INPUT
-10
-10
-20
-20
-30
-50 -30 -10
10
30
50
SIGNAL VOLTAGE AT SOURCE AND PIN (V)
Figure 2. Input Clamp Characteristics
-30
-8 -6 -4 -2 0 2 4 6 8
SIGNAL VOLTAGE AT SOURCE AND PIN (V)
Figure 3. Input Clamp Characteristics (Zoom In)
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