MAX11047 Datasheet, PDF (10/18 Pages) Maxim Integrated Products – 4-/6-/8-Channel, 16-Bit, Simultaneous-Sampling ADCs

4-/6-/8-Channel, 16-Bit,
Simultaneous-Sampling ADCs
Pin Description (continued)
PIN
NAME
FUNCTION
42
CH6
Channel 6 Analog Input for MAX11049. Channel 5 for MAX11048.
45
CH7
Channel 7 Analog Input for MAX11049
52
WR
Active-Low Write Input. Drive WR low to write to the ADC. Configuration registers are loaded on the
rising edge of WR.
53
CS
Active-Low Chip-Select Input. Drive CS low when reading from or writing to the ADC.
54
RD
Active-Low Read Input. Drive RD low to read from the ADC. Each rising edge of RD advances the
channel output on the data bus.
55
DB15 16-Bit Parallel Data Bus Digital Out Bit 15
56
DB14 16-Bit Parallel Data Bus Digital Out Bit 14
—
EP
Exposed Pad. Internally connected to AGND. Connect to a large ground plane to maximize thermal
performance. Not intended as an electrical connection point.
Detailed Description
The MAX11047/MAX11048/MAX11049 are fast, low-
power ADCs that combine 4, 6, or 8 independent ADC
channels in a single IC. Each channel includes simulta-
neously sampling independent T/H circuitry that pre-
serves relative phase information between inputs
making the MAX11047/MAX11048/MAX11049 ideal for
motor control and power monitoring. The MAX11047/
MAX11048/MAX11049 are available with a 0 to 5V input
range that features ±20mA overrange, fault-tolerant
inputs. The MAX11047/MAX11048/MAX11049 operate
with a single 4.75V to 5.25V supply. A separate 2.7V to
5.25V supply for digital circuitry makes the devices
compatible with low-voltage processors.
The MAX11047/MAX11048/MAX11049 perform conver-
sions for all channels in parallel by activating indepen-
dent ADCs. Results are available through a high-speed,
20MHz, parallel data bus after a conversion time of 3μs
following the end of a sample. The data bus is bidirec-
tional and allows for easy programming of the configura-
tion register. The MAX11047/MAX11048/MAX11049
feature a reference buffer, which is driven by an internal
bandgap reference circuit (V_REFIO = 4.096V). Drive
REFIO with an external reference or bypass with a 0.1μF
capacitor to ground when using the internal reference.
Analog Inputs
Track and Hold (T/H)
To preserve phase information across all channels,
each input includes a dedicated T/H circuitry. The input
tracking circuitry provides a 4MHz small-signal band-
width, enabling the device to digitize high-speed tran-
sient events and measure periodic signals with
bandwidths exceeding the ADC’s sampling rate by
using undersampling techniques. Use anti-alias filtering
to avoid high-frequency signals being aliased into the
frequency band of interest.
Input Range and Protection
The full-scale analog input voltage is a product of the
reference voltage. For MAX11047/MAX11048/
MAX11049, the input is unipolar in the range of:
0
to
+ V_REFIO
x
5.0
4.096
In external reference mode, drive V_REFIO with a 3.0V to
4.25V source, resulting in a full-scale input range of
3.662V to 5.188V, respectively.
All analog inputs are fault-protected up to ±20mA. The
MAX11047/MAX11048/MAX11049 include an input
clamping circuit that activates when the input voltage at
the analog input is above (V_AVDD + 300mV) or below
-300mV. The clamp circuit remains high impedance
while the input signal is within the range of 0V to
+V_AVDD and draws little to no current. However, when
the input signal exceeds the range of 0V to +V_AVDD,
the clamps begin to turn on. Consequently, to obtain
the highest accuracy, ensure that the input voltage
does not exceed the range of 0V to +V_AVDD.
To make use of the input clamps, connect 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 MAX11047/MAX11048/MAX11049 does
not exceed ±20mA. Note that the voltage at the analog
input pin limits to approximately 7V during a fault condi-
tion so the following equation can be used to calculate
the value of R_S:
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