General Description
The MAX1415/MAX1416 low-power, 2-channel, serial-output analog-to-digital converters (ADCs) use a sigma-delta modulator with a digital filter to achieve 16-bit resolution with no missing codes. These ADCs are pin-compatible upgrades to the MX7705/AD7705. The MAX1415/MAX1416 feature an internal oscillator (1MHz or 2.4576MHz), an on-chip input buffer, and a program-mable gain amplifier (PGA). The devices offer an SPI?-/QSPI?-/MICROWIRE?-compatible serial interface.
The MAX1415 requires a single 2.7V to 3.6V supply, and the MAX1416 requires a single 4.75V to 5.25V supply.The operating supply current is 400μA (max) with a 3V supply. Power-down mode reduces the supply current to 2μA (typ). When operating with a supply of 3V, the power dissipation is less than 1.44mW, making the MAX1415ideal for battery-powered applications.
Self-calibration and system calibration allow the MAX1415/MAX1416 to correct for gain and offset errors.Excellent DC performance (±0.0015% FSR INL) and low noise (700nV in unbuffered mode) make the MAX1415/MAX1416 ideal for measuring low-frequency signals with a wide dynamic range. These devices accept fully differ-ential bipolar/unipolar inputs. An internal input buffer allows for input signals with high source impedances. An on-chip digital filter, with a programmable cutoff and out-put data rate, processes the output of the sigma-delta modulator. The first notch frequency of the digital filter is chosen to provide 150dB rejection of common-mode 50Hz or 60Hz noise and 98dB rejection of normal-mode 50Hz or 60Hz noise. A PGA and digital filtering allow sig-nals to be directly acquired with little or no signal-condi-tioning requirements.
The MAX1415/MAX1416 are available in 16-pin PDI P,SO, and TSSOP packages.
Applications
Industrial Instruments Weigh Scales
Strain-Gauge Measurements Loop-Powered Systems Flow and Gas Meters Medical Instrumentation Pressure Transducers Thermocouple Measurements RTD Measurements
Features
?16-Bit Sigma-Delta ADCs
?Two Fully Differential Input Channels
?0.0015% Integral Nonlinearity with No Missing Codes
?Internal Analog Input Buffers
?Programmable Gain Amplifier (PGA) from 1 to 128?Internal Oscillator (2.4576MHz or 1MHz)
?Single 2.7V to 3.6V (MAX1415) or 4.75V to 5.25V (MAX1416) Supply ?Low Power
1mW max, 3V Supply
2μA (typ) Power-Down Current
?SPI?-/QSPI?-/MICROWIRE?-Compatible 3-Wire Serial Interface
?Pin Compatible with MX7705/AD7705?16-Pin PDIP, SO, and TSSOP Packages
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
________________________________________________________________Maxim Integrated Products 1
Pin Configuration
Ordering Information
19-3163; Rev 1; 12/05
For pricing, delivery, and ordering information,please contact Maxim/Dallas Direct!at 1-888-629-4642, or visit Maxim’s website at https://www.doczj.com/doc/4e14747087.html,.
SPI/QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
Ordering Information continued at end of data sheet.
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs 2_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS—MAX1415
(V DD = 3V, GND = 0, V REF+= 1.225V, V REF-= GND, external f CLKIN = 2.4576MHz, CLKDIV bit = 0, C REF+to GND = 0.1μF, C REF-to
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
V DD to GND..............................................................-0.3V to +6V All Other Pins to GND.................................-0.3V to (V DD + 0.3V)Maximum Current Input into Any Pin..................................50mA Continuous Power Dissipation (T A = +70°C)
16-Pin PDIP (derate 10.5mW/°C above +70°C)...........842mW 16-Pin TSSOP (derate 9.4mW/°C above +70°C).........755mW 16-Pin Wide SO (derate 9.5mW/°C above +70°C)......762mW
Operating Temperature Range ..........................-40°C to +85°C Storage Temperature Range.............................-60°C to +150°C Junction Temperature......................................................+150°C Lead Temperature (soldering, 10s).................................+300°C
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
ELECTRICAL CHARACTERISTICS—MAX1415 (continued)
(V DD = 3V, GND = 0, V REF+= 1.225V, V REF-= GND, external f CLKIN = 2.4576MHz, CLKDIV bit = 0, C REF+to GND = 0.1μF, C REF-to
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs
ELECTRICAL CHARACTERISTICS—MAX1415 (continued)
(V DD = 3V, GND = 0, V REF+= 1.225V, V REF-= GND, external f CLKIN = 2.4576MHz, CLKDIV bit = 0, C REF+to GND = 0.1μF, C REF-to
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
_______________________________________________________________________________________5
ELECTRICAL CHARACTERISTICS—MAX1415 (continued)
(V DD = 3V, GND = 0, V REF+= 1.225V, V REF-= GND, external f CLKIN = 2.4576MHz, CLKDIV bit = 0, C REF+to GND = 0.1μF, C REF-to GND = 0.1μF, T A = T MIN to T MAX , unless otherwise noted.)
ELECTRICAL CHARACTERISTICS—MAX1416
(V DD = 5V, GND = 0, V REF+= 2.5V, V REF-= GND, f CLKIN = 2.4576MHz, CLKDIV bit = 0, C REF+to GND = 0.1μF, C REF-to GND =0.1μF, T
= T to T , unless otherwise noted.)
TIMING CHARACTERISTICS—MAX1415
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs 6_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS—MAX1416 (continued)
(V DD = 5V, GND = 0, V REF+= 2.5V, V REF-= GND, f CLKIN = 2.4576MHz, CLKDIV bit = 0, C REF+to GND = 0.1μF, C REF-to GND =
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
_______________________________________________________________________________________7
ELECTRICAL CHARACTERISTICS—MAX1416 (continued)
(V DD = 5V, GND = 0, V REF+= 2.5V, V REF-= GND, f CLKIN = 2.4576MHz, CLKDIV bit = 0, C REF+to GND = 0.1μF, C REF-to GND =0.1μF, T A = T MIN to T MAX , unless otherwise noted.)
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs
ELECTRICAL CHARACTERISTICS—MAX1416 (continued)
(V DD = 5V, GND = 0, V REF+= 2.5V, V REF-= GND, f CLKIN = 2.4576MHz, CLKDIV bit = 0, C REF+to GND = 0.1μF, C REF-to GND =0.1μF, T = T to T , unless otherwise noted.)
(Note 16) (Figures 8, 9)
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
_______________________________________________________________________________________9
temperature.
Note 2:Recalibration at any temperature removes these drift errors.
Note 3:Positive full-scale error includes zero-scale errors (unipolar offset error or bipolar zero error) and applies to both unipolar
and bipolar input ranges.
Note 4:Full-scale drift includes zero-scale drift (unipolar offset drift or bipolar zero drift) and applies to both unipolar and bipolar
input ranges.
Note 5:Gain error does not include zero-scale errors. It is calculated as (full-scale error – unipolar offset error) for unipolar ranges,
and (full-scale error – bipolar zero error) for bipolar ranges.
Note 6:Gain-error drift does not include unipolar offset drift or bipolar zero drift. Effectively, it is the drift of the part if only zero-scale calibrations are performed.
Note 7:The analog input voltage range on AIN+ is given here with respect to the voltage on AIN- on the MAX1415/MAX1416.
Note 8:This common-mode voltage range is allowed, provided that the input voltage on the analog inputs does not go more posi-tive than (V DD + 30mV) or more negative than (GND - 30mV). Parts are functional with voltages down to (GND - 200mV),but with increased leakage at high temperature.
Note 9: The REF differential voltage, V REF , is the voltage on REF+ referenced to REF- (V REF = V REF+- V REF-).Note 10:Guaranteed by design.
Note 11:These calibration and span limits apply, provided that the absolute voltage on the analog inputs does not exceed (V DD +
30mV) or go more negative than (GND - 30mV). The offset-calibration limit applies to both the unipolar zero point and the bipolar zero point.
Note 12:When using a crystal or ceramic resonator across the CLKIN and CLKOUT as the clock source for the device, the supply
current and power dissipation varies depending on the crystal or resonator type. Supply current is measured with the digi-tal inputs connected to 0 or V DD , CLKIN connected to an external clock source, and CLKDIS = 1.
Note 13:If the external master clock continues to run in power-down mode, the power-down current typically increases to 67μA at
3V. When using a crystal or ceramic resonator across the CLKI N and CLKOUT as the clock source for the device, the clock generator continues to run in power-down mode and the power dissipation depends on the crystal or resonator type (see the Power-Down Modes section).
Note 14:Measured at DC and applied in the selected passband. PSRR at 50Hz exceeds 120dB with filter notches of 25Hz or 50Hz.
PSRR at 60Hz exceeds 120dB with filter notches of 20Hz or 60Hz.
Note 15:CLKIN higher-than-specified current and can possibly become uncalibrated.
Note 16:All input signals are specified with t r = t f = 5ns (10% to 90% of V DD ) and timed from a voltage level of 1.6V.
TIMING CHARACTERISTICS—MAX1416 (continued)
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs 10______________________________________________________________________________________
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
______________________________________________________________________________________11
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs 12______________________________________________________________________________________
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
______________________________________________________________________________________13
Table 4. MAX1416—Peak-to-Peak Resolution vs. Gain and Output Data Rate (5V)
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs 14______________________________________________________________________________________
5.15
5.05
4.95
4.85
-0.002-0.00100.001
0.0020.003-0.003
4.75
5.25OFFSET ERROR vs. SUPPLY VOLTAGE
(MAX1416)
M A X 1415/M A X 1416 t o c 04
SUPPLY VOLTAGE (V)O F F S E T E R R O R (%F S R )
603510-15-0.002-0.00100.001
0.0020.003-0.003
-4085OFFSET ERROR vs. TEMPERATURE
TEMPERATURE (°C)O F F S E T E R R O R (%F S R )
GAIN ERROR vs. SUPPLY VOLTAGE
(MAX1415)
M A X 1415/M A X 1416 t o c 06
SUPPLY VOLTAGE (V)
G A I N E R R O R (%F S R )
3.453.303.153.002.85-0.0010-0.000500.0005
0.00100.0015-0.0015
2.70
3.60
GAIN ERROR vs. SUPPLY VOLTAGE
(MAX1416)
M A X 1415/M A X 1416 t o c 07
SUPPLY VOLTAGE (V)
G A I N E R R O R (%F S R )
5.15
5.05
4.95
4.85
-0.002-0.00100.001
0.0020.003-0.003
4.75
5.25
GAIN ERROR vs. TEMPERATURE
TEMPERATURE (°C)
G A I N E R R O R (%F S R )
60
35
10
-15
-0.004
-0.003-0.002-0.00100.001
0.0020.0030.0040.005
-0.005
-40
85
TYPICAL OUTPUT NOISE (MAX1416, BUFFERED MODE)
READING NUMBER
C O
D
E R E A D 1600120080040032758
32760327623276432766327683277032772327743277632756
2000
HISTOGRAM OF TYPICAL OUTPUT NOISE
(MAX1416, BUFFERED MODE)
CODE
O C C U R R E N C E
32773277327732773276327632763276327632764327633276232761100
200
300400
032760OFFSET ERROR vs. SUPPLY VOLTAGE
(MAX1415)
M A X 1415/M A X 1416 t o c 03
SUPPLY VOLTAGE (V)
O F F S E T E R R O R (%F S R )
3.45
3.30
3.15
3.00
2.85
-0.0010
-0.000500.0005
0.00100.0015-0.0015
2.70
3.60
Typical Operating Characteristics
(MAX1415: V DD = 5V, V REF+= 2.5V, V REF-= GND, T A = +25°C, unless otherwise noted.) (MAX1416: V DD = 3V, V REF+= 1.225V,V REF-= GND, T A = +25°C, unless otherwise noted.)
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
______________________________________________________________________________________
15
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(MAX1415)
SUPPLY VOLTAGE (V)
S U P P L Y C U R R E N T (m A )
3.45
3.30
3.15
3.00
2.85
0.3
0.4
0.5
A: BUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 8 TO 128B: BUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 1 TO 4E: UNBUFFERED MODE f CLKIN = 1MHz, GAIN = 1 TO 128
C: BUFFERED MODE f CLKIN = 1MHz, GAIN = 1 TO 128D: UNBUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 1 TO 1280.6
0.22.70
3.60
5.155.054.954.850.35
0.45
0.55
0.65
0.25
4.75
5.25
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(MAX1416)
SUPPLY VOLTAGE (V)
S U P P L Y C U R R E N T (m A )
A: BUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 8 TO 128B: BUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 1 TO 4E: UNBUFFERED MODE f CLKIN = 1MHz, GAIN = 1 TO 128
C: BUFFERED MODE f CLKIN = 1MHz, GAIN = 1 TO 128D: UNBUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 1 TO 12860
35
10
-15
0.3
0.4
0.5
0.6
0.2-40
85
SUPPLY CURRENT vs. TEMPERATURE
(MAX1415)
TEMPERATURE (°C)
S U P P L Y C U R R E N T (m A )
A: BUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 8 TO 128B: BUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 1 TO 4E: UNBUFFERED MODE f CLKIN = 1MHz, GAIN = 1 TO 128
C: BUFFERED MODE f CLKIN = 1MHz, GAIN = 1 TO 128D: UNBUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 1 TO 12860
35
10
-15
0.35
0.45
0.55
0.65
0.25
-40
85
SUPPLY CURRENT vs. TEMPERATURE
(MAX1416)
TEMPERATURE (°C)
S U P P L Y C U R R E N T (m A )
A: BUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 8 TO 128B: BUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 1 TO 4E: UNBUFFERED MODE f CLKIN = 1MHz, GAIN = 1 TO 128
C: BUFFERED MODE f CLKIN = 1MHz, GAIN = 1 TO 128D: UNBUFFERED MODE f CLKIN = 2.4576MHz, GAIN = 1 TO 128Typical Operating Characteristics (continued)
(MAX1415: V DD = 5V, V REF+= 2.5V, V REF-= GND, T A = +25°C, unless otherwise noted.) (MAX1416: V DD = 3V, V REF+= 1.225V,V REF-= GND, T A = +25°C, unless otherwise noted.)
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs 16______________________________________________________________________________________
SUPPLY CURRENT vs. f CLKIN
(MAX1415)
f CLKIN (MHz) 2.42.22.01.81.61.41.21.00.80.60.4 2.6
0.3
0.4
0.5
0.6
0.2
S U P P L Y C U R R E N T (m A )
A: BUFFERED MODE CLK = 1, GAIN = 128
B: BUFFERED MODE CLK = 1, GAIN = 1
E: UNBUFFERED MODE CLK = 0, GAIN = 1, 128
C: BUFFERED MODE CLK = 0, GAIN = 1, 128
D: UNBUFFERED MODE CLK = 1, GAIN = 1, 128SUPPLY CURRENT vs. f CLKIN
(MAX1416)
f CLKIN (MHz) 2.42.22.01.81.61.41.21.00.80.60.4 2.6
0.35
0.45
0.55
0.65
0.25
S U P P L Y C U R R E N T (m A )
A: BUFFERED MODE CLK = 1, GAIN = 128
B: BUFFERED MODE CLK = 1, GAIN = 1
E: UNBUFFERED MODE
CLK = 0, GAIN = 1, 128
C: BUFFERED MODE CLK = 0, GAIN = 1, 128
D: UNBUFFERED MODE CLK = 1, GAIN = 1, 128GAIN
64
32
16
8
4
2
1
128
SUPPLY CURRENT vs. GAIN
(MAX1415)
0.3
0.4
0.5
0.6
0.2
S U P P L Y C U R R E N T (m A )
A: BUFFERED MODE CLK = 1, CLKDIV = 1, f CLKIN = 4.9152MHz B: BUFFERED MODE CLK = 1, CLKDIV = 0, f CLKIN = 2.4576MHz E: UNBUFFERED MODE CLK = 1, CLKDIV = 0, f CLKIN = 2.4576MHz F: UNBUFFERED MODE CLK = 0, CLKDIV = 0, f CLKIN = 1MHz
C: BUFFERED MODE CLK = 0, CLKDIV = 0, f CLKIN = 1MHz D: UNBUFFERED MODE CLK = 1, CLKDIV = 1, f CLKIN = 4.9152MHz GAIN
64
32
16
8
4
2
1
128
SUPPLY CURRENT vs. GAIN
(MAX1416)
0.35
0.45
0.55
0.65
0.25
S U P P L Y C U R R E N T (m A )
A: BUFFERED MODE CLK = 1, CLKDIV = 1, f CLKIN = 4.9152MHz B: BUFFERED MODE CLK = 1, CLKDIV = 0, f CLKIN = 2.4576MHz E: UNBUFFERED MODE CLK = 1, CLKDIV = 0, f CLKIN = 2.4576MHz F: UNBUFFERED MODE CLK = 0, CLKDIV = 0, f CLKIN = 1MHz
C: BUFFERED MODE CLK = 0, CLKDIV = 0, f CLKIN = 1MHz D: UNBUFFERED MODE CLK = 1, CLKDIV = 1, f CLKIN = 4.9152MHz Typical Operating Characteristics (continued)
(MAX1415: V DD = 5V, V REF+= 2.5V, V REF-= GND, T A = +25°C, unless otherwise noted.) (MAX1416: V DD = 3V, V REF+= 1.225V,V REF-= GND, T A = +25°C, unless otherwise noted.)
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs
______________________________________________________________________________________17
POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE (MAX1415)
SUPPLY VOLTAGE (V)
P O W E R -D O W N S U P P L Y C U R R E N T (n A )
3.45
3.30
3.15
3.00
2.85
2040608010002.70
3.60
M A X 1415/M A X 1416 t o c 17
5.15
5.05
4.95
4.85
120
140
160
180
200100
4.75
5.25
POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE (MAX1416)
SUPPLY VOLTAGE (V)
P O W E R -D O W N S U P P L Y C U R R E N T (n A )
M A X 1415/M A X 1416 t o c 18
POWER-DOWN SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
P O W E R -D O W N S U
P P L Y C U R R E N T (n A )
603510-15501001502002503000
-4085
EXTERNAL OSCILLATOR STARTUP TIME
2ms/div
V DD 5V/div
CLKOUT 5V/div CLKOUT 5V/div
INTERNAL OSCILLATOR STARTUP TIME
4μs/div
SCLK 5V/div CLKOUT 5V/div CLK = 1CLKOUT 5V/div CLK = 0
Typical Operating Characteristics (continued)
(MAX1415: V DD = 5V, V REF+= 2.5V, V REF-= GND, T A = +25°C, unless otherwise noted.) (MAX1416: V DD = 3V, V REF+= 1.225V,V REF-= GND, T A = +25°C, unless otherwise noted.)
M A X 1415/M A X 1416
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs 18______________________________________________________________________________________
Pin Description
Detailed Description The MAX1415/MAX1416 low-power, 2-channel serial output ADCs use a sigma-delta modulator with a digital filter to achieve 16-bit resolution with no missing codes. Each device includes a PGA, an on-chip input buffer, an internal oscillator, and a bidirectional communica-tions port. The MAX1415 operates with a 2.7V to 3.6V single supply, and the MAX1416 operates with a 4.75V to 5.25V single supply.
Fully differential inputs, an internal input buffer, and an on-chip PGA (gain = 1 to 128) allow low-level signals to be directly measured, minimizing the requirements for external signal conditioning. Self-calibration corrects for gain and offset errors. A programmable digital filter allows for the selection of the output data rate and first notch frequency from 20Hz to 500Hz.
The bidirectional serial SPI-/QSPI-/MICROWIRE-compati-ble interface consists of four digital control lines (SCLK, CS, DOUT, and DIN) and provides an easy interface to microcontrollers (μCs). Connect CS to GND to configure the MAX1415/MAX1416 for 3-wire operation.
Analog Inputs
The MAX1415/MAX1416 accept four analog inputs
(AI N1+, AI N1-, AI N2+, and AI N2-) in buffered or unbuffered mode. Use Table8 to select the positive
and negative input pair for a fully differential channel.
The input buffer isolates the inputs from the capacitive
load presented by the PGA/modulator, allowing for high source-impedance analog transducers. The value of
the BUF bit in the setup register (see the Setup Register section) determines whether the input buffer is enabled
or disabled.
I nternal protection diodes, which clamp the analog
input to V DD and/or GND, allow the input to swing from (GND - 0.3V) to (V DD+ 0.3V), without damaging the device. If the analog input exceeds 300mV beyond the supplies, limit the input current to 10mA.
Input Buffers
When the analog input buffer is disabled, the analog
input drives a typical 7pF (gain = 1) capacitor, C TOTAL,
in series with the 7k?typical on-resistance of the track
and hold (T/H) switch (Figure1). C TOTAL is comprised
of the sampling capacitor, C SAMP, and the stray capac-itance, C STRAY. During the conversion, C SAMP charges
to (AI N+ - AI N-). The gain determines the value of
C SAMP(see Table5).
MAX1415/MAX1416
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADCs ______________________________________________________________________________________19
M A X 1415/M A X 1416
To minimize gain errors in unbuffered mode, select a source impedance less than the maximum values shown in Figures 2 and 3. These are the maximum external resistance/capacitance combinations allowed before gain errors greater than 1 LSB are introduced in unbuffered mode.
Enable the internal input buffer for a high source imped-ance. This isolates the inputs from the sampling capaci-tor and reduces the sampling-related gain error. When using the internal buffer, limit the absolute input voltage range to (V GND + 50mV) to (V DD - 1.5V). Properly set up the gain and common-mode voltage range to mini-mize linearity errors.
Input Voltage Range
In unbuffered mode, the absolute analog input voltage range is from (GND - 30mV) to (V DD + 30mV) (see the Electrical Characteristics section). I n buffered mode,the analog input voltage range is reduced to (GND +50mV) to (V DD - 1.5V). In both buffered and unbuffered modes, the differential analog input range (V AIN+- V AIN-)decreases at higher gains (see the Programmable Gain Amplifier and Unipolar and Bipolar Modes sections).
Reference
The MAX1415/MAX1416 provide differential inputs,REF+ and REF-, for an external reference voltage.Connect the external reference directly across REF+ and REF- to obtain the differential reference voltage, V REF .The common-mode voltage range for V REF+and V REF-is between GND and V DD . For specified operation, the nominal voltage, V REF is 1.225V for the MAX1415 and 2.5V for the MAX1416.
The MAX1415/MAX1416 sample REF+ and REF- at f CLKIN /64 (CLKDI V = 0) or f CLKIN /128 (CLKDI V = 1)with an internal 10pF (typ for gain = 1) sampling capac-itor in series with a 7k ?(typ) switch on-resistance.
Programmable Gain Amplifier
A PGA provides selectable levels of gain: 1, 2, 4, 8, 16,32, 64, and 128. Bits G0, G1, and G2 in the setup reg-ister control the gain (see Table 9). As the gain increas-es, the value of the input sampling capacitor, C SAMP ,also increases (see Table 5). The dynamic load pre-sented to the analog inputs increases with clock fre-quency and gain in unbuffered mode (see the Input Buffers section and Figure 1).
16-Bit, Low-Power, 2-Channel, Sigma-Delta ADCs 20