MAX1157 Datasheet, PDF (7/15 Pages) Maxim Integrated Products – 14-Bit, 135ksps, Single-Supply ADCs with Bipolar Analog Input Range

14-Bit, 135ksps, Single-Supply ADCs with
Bipolar Analog Input Range
PIN
15
16
17
18
19
20
21, 22
23
24
25
26
27
28
NAME
REFADJ
REF
RESET
CS
DGND
DV_DD
N.C.
D0
D1
D2
D3
D4
D5
Pin Description (continued)
FUNCTION
Reference Buffer Output. Bypass REFADJ with a 0.1µF capacitor to AGND for internal reference
mode. Connect REFADJ to AV_DD to select external reference mode.
Reference Input/Output. Bypass REF with a 10µF capacitor to AGND. REF is the external reference
input when in external reference mode.
Reset Input. Logic high resets the device.
Convert Start. The first falling edge of CS powers up the device and enables acquisition when R/C
is low. The second falling edge of CS starts conversion. The third falling edge of CS loads the result
onto the bus when R/C is high.
Digital Ground
Digital Supply Voltage. Bypass with a 0.1µF capacitor to DGND.
No Connection. Make no connection to these pins.
Three-State Digital Data Output (LSB)
Three-State Digital Data Output
Three-State Digital Data Output
Three-State Digital Data Output
Three-State Digital Data Output
Three-State Digital Data Output
Detailed Description
Converter Operation
The MAX1157/MAX1159/MAX1175 use a successive-
approximation (SAR) conversion technique with an
inherent track-and-hold (T/H) stage to convert an analog
input into a 14-bit digital output. Parallel outputs provide
a high-speed interface to microprocessors (µPs). The
Functional Diagram at the end of the data sheet shows a
simplified internal architecture of the MAX1157/
MAX1159/MAX1175. Figure 3 shows a typical applica-
tion circuit for the MAX1157/MAX1159/MAX1175.
Analog Input
Input Scaler
The MAX1157/MAX1159/MAX1175 have an input scaler
which allows conversion of true bipolar input voltages
and input voltages greater than the power supply, while
operating from a single +5V analog supply. The input
scaler attenuates and shifts the analog input to match
the input range of the internal DAC. The MAX1157 has
a unipolar input voltage range of 0 to +10V. The
DV_DD
1mA
D0–D13
1mA
C_LOAD = 20pF
D0–D13
DGND
C_LOAD = 20pF
DGND
A) HIGH-Z TO V_OH,
V_OL TO V_OH, AND
V_OH TO HIGH-Z
B) HIGH-Z TO V_OL,
V_OH TO V_OL, AND
V_OL TO HIGH-Z
Figure 1. Load Circuits
MAX1175 input voltage range is ±5V while the
MAX1159 input voltage range is ±10V. Figure 4 shows
the equivalent input circuit of the MAX1157/
MAX1159/MAX1175. This circuit limits the current going
into or out of AIN to less than 1.8mA.
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