MAXIM MAX1117, MAX1118, MAX1119 Technical data

General Description

The MAX1117/MAX1118/MAX1119 low-power, 8-bit, dual-channel, analog-to-digital converters (ADCs) feature an internal track/hold (T/H) voltage reference (MAX1117/MAX1119), clock, and serial interface. The MAX1118 is specified from +2.7V to +5.5V and consumes only 135µA at 100ksps. The MAX1117 is specified from +2.7V to +3.6V, and the MAX1119 is specified from +4.5V to +5.5V, each consumes only 175µA at 100ksps.

The full-scale analog input range is determined by the internal reference of +2.048V (MAX1117) or +4.096V (MAX1119), or by an externally applied reference ranging from +1V to VDD(MAX1118). All devices feature an automatic shutdown mode that reduces supply current to <1µA when the device is not in use. The 3-wire serial interface directly connects to SPI™, QSPI™, and MICROWIRE™ devices without external logic. Conversions up to 100ksps are performed using an internal clock.

The MAX1117/MAX1118/MAX1119 are available in an 8-pin SOT23 package with a footprint that is only 11% of an 8-pin plastic DIP.

________________________Applications

Low-Power, Handheld Portable Devices

System Diagnostics

Battery-Powered Test Equipment

Solar-Powered Remote Systems

Receive Signal Strength Indicators

4mA to 20mA Powered Remote Data Acquisition Systems

Features

♦ Single Supply

+2.7V to +3.6V (MAX1117) +2.7V to +5.5V (MAX1118) +4.5V to +5.5V (MAX1119)

♦ Internal Track/Hold: 100kHz Sampling Rate

♦ Internal Reference

+2.048V (MAX1117) +4.096V (MAX1119)

♦ Reference Input Range: 0 to V

(MAX1118)

♦ SPI/QSPI/MICROWIRE-Compatible Serial Interface

♦ Small 8-Pin SOT23 Package

♦ Automatic Power-Down

♦ Analog Input Range: 0 to V

REF

♦ Low Power

175µA at 100ksps (typ) (MAX1117/MAX1119) 135µA at 100ksps (typ) (MAX1118) 18µA at 10ksps (typ) 1µA (typ) in Power-Down Mode

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power,

2-Channel, Serial 8-Bit ADCs

________________________________________________________________ Maxim Integrated Products 1

SCLK

DOUT

CNVST

GND

( ) ARE FOR MAX1118 ONLY

CH1

CHO

MAX1117 MAX1118 MAX1119

SOT23

TOP VIEW

(REF) I.C

Pin Configuration

19-1857; Rev 0; 11/00

EVALUATION KIT

AVAILABLE

Ordering Information

PART

TEMP. RANGE

PIN-

TO P

M A RK

M A X1 1 1 7 EKA

8 SOT23

M A X1 1 1 8 E K A

8 SOT23 AADX

M A X1 1 1 9 E K A

8 SOT23 AADY

SPI/QSPI are trademarks of Motorola, Inc.

MICROWIRE is a trademark of National Semiconductor, Corp.

Functional Diagram appears at end of data sheet.

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.

PA CK A G E

-40°C to +85°C

AADW

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VDD= +2.7V to +3.6V (MAX1117), VDD= +4.5V to +5.5V (MAX1119), VDD= REF = +2.7V to +5.5V (MAX1118),TA= T

MIN

to T

MAX

unless otherwise noted.)

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.

VDDto GND...........................................................-0.3V to +6.0V

CH0,CH1, REF to GND...............................-0.3V to (V

+ 0.3V)

Digital Output to GND ................................-0.3V to (V

+ 0.3V)

Digital Input to GND ..............................................-0.3V to +6.0V

Maximum Current into Any Pin .........................................±50mA

Continuous Power Dissipation (T

= +70°C)

8-Pin SOT23 (derate 8.9mW/°C above +70°C)............714mW

Operating Temperature Range

MAX1117EKA ..................................................-40°C to + 85°C

MAX1118EKA ..................................................-40°C to + 85°C

MAX1119EKA ..................................................-40°C to + 85°C

Storage Temperature Range .............................-60°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

PARAMETER

SYMBOL

CONDITIONS

MIN TYP MAX

UNITS

DC ACCURACY

Resolution

Bits

Relative Accuracy (Note 1) INL

Differential Nonlinearity DNL

Offset Error

MAX1118, REF = V

Gain Error

MAX1117/MAX1119

MAX1118

Gain Temperature Coefficient

MAX1117/MAX1119

Total Unadjusted Error TUE MAX1118

Channel-to-Channnel Offset Matching

DYNAMIC PERFORMANCE (25kHz sinewave input, VIN = V

REF(pp)

, f

SCLK

= 5MHz, f

sample

= 100ksps, RIN = 100Ω)

Signal-to-Noise Plus Distortion

Total Harmonic Distortion (Up to the 5th Harmonic)

THD

Spurious-Free Dynamic Range SFDR

Small Signal Bandwidth f

-3dB

ANALOG INPUT

Input Voltage Range

Input Leakage Current

_ = 0 or V

Input Capacitance C

INTERNAL REFERENCE

MAX1117

Voltage V

REF

MAX1119

SINAD

±0.5

±5

±90

±0.5 ±1

±0.1 LSB

-69

±0.7 ±10 µA

2.048

4.096

±1

±5

REF

LSB

%FSR

ppm/°C

LSB

MHz

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power,

2-Channel, Serial 8-Bit ADCs

_______________________________________________________________________________________ 3

PARAMETER

SYMBOL

CONDITIONS

MIN TYP MAX

UNITS

EXTERNAL REFERENCE (MAX1118 ONLY)

Input Voltage Range

Input Current Ave, VDD = REF = +5.5V at 100ksps

µA

POWER REQUIREMENTS

MAX1118

MAX1117

Supply Voltage V

MAX1119

MAX1119, f

SAMPLE

= 100ksps,

zero-scale input

MAX1117/MAX1118, f

SAMPLE

= 100ksps,

zero-scale input

MAX1119, f

SAMPLE

= 10ksps,

zero-scale input

MAX1117/MAX1118, f

SAMPLE

= 10ksps,

zero-scale input

Supply Current (Note 2) I

Shutdown

µA

Supply Rejection Ratio PSRR Full-scale or 0 input

LSB/V

DIGITAL INPUTS (CNVST AND SCLK)

Input High Voltage V

Input Low Voltage V

Input Hystersis

Input Current High I

µA

Input Current Low I

µA

Input Capacitance C

DIGITAL OUTPUT (DOUT)

Output High Voltage V

SOURCE

= 2mA

SINK

= 2mA

Output Low Voltage V

SINK

= 4mA

Three-State Leakage Current I

µA

Three-State Output Capacitance

OUT

TIMING CHARACTERISTICS (Figures 6a–6d)

CNVST High Time t

csh

CNVST Low Time t

csi

Conversion Time t

conv

µs

Serial Clock High Time t

Serial Clock Low Time t

Serial Clock Period t

Falling of CNVST to DOUT Active

csd

LOAD

= 100pF, Figure 1

ELECTRICAL CHARACTERISTICS (continued)

(VDD= +2.7V to +3.6V (MAX1117), VDD= +4.5V to +5.5V (MAX1119), VDD= REF = +2.7V to +5.5V (MAX1118),TA= T

MIN

to T

MAX

unless otherwise noted.)

HYST

1.0 V

10 20

2.7 5.5

4.5 5.5

182 230

135 190

19 25

14 21

0.8 10

±0.5 ±1

0.8

0.2

±10

VDD - 0.5

100

200

0.4

0.8

±0.01 ±10

7.5

100

Typical Operating Characteristics

(VDD= +3V (MAX1117), VDD= +5V (MAX1119), VDD= V

REF

= +3V (MAX1118), f

SCLK

= 5MHz, f

SAMPLE

= 100ksps, C

LOAD

= 100pF,

TA = +25°C, unless otherwise noted.)

MAX1117/18/19 toc01

-1.0

-0.4

-0.6

-0.8

-0.2

0.2

0.4

0.6

0.8

1.0

0 10050 150 200 250 300

INTEGRAL NONLINEARITY

vs.OUTPUT CODE

OUTPUT CODE

INL (LSB)

010050 150 200 250 300

DIFFERENTIAL NONLINEARITY

vs.OUTPUT CODE

MAX1117/18/19 toc02

OUTPUT CODE

DNL (LSB)

-1.0

-0.4

-0.6

-0.8

-0.2

0.2

0.4

0.6

0.8

1.0

0.2

0.1

0.4

0.3

0.6

0.5

0.7

SHUTDOWN SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX1117/18/19 toc03

SUPPLY VOLTAGE (V)

SHUTDOWN CURRENT (μA)

2.5 3.5 4.5 5.5

0.1

0.01 0.1 1 10 100

MAX1118

SUPPLY CURRENT vs. CONVERSION RATE

1.0

MAX1117/18/19 toc04

CONVERSION (ksps)

SUPPLY CURRENT (μA)

100.0

10.0

VDD = V

REF

= V

DIGITAL

VDD = +5V

VDD = +3V

MAX1117/18/19 toc05

110

120

140

160

2.5 3.5 4.5 5.5

MAX1118

SUPPLY CURRENT vs. SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (μA)

OUT

= 00000000

= V

REF

= V

DIGITAL INPUTS

100

150

-40 -15 10 35 60 85

MAX1118 SUPPLY CURRENT

vs. TEMPERATURE

MAX1117/18/19 toc06

TEMPERATURE (°C)

SUPPLY CURRENT (μA)

OUT

= 00000000

= V

REF

= V

DIGITAL INPUTS

VDD = +5V

VDD = +3V

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs

4 _______________________________________________________________________________________

PARAMETER

SYMBOL

CONDITIONS

MIN TYP MAX

UNITS

Serial Clock Falling Edge to DOUT

LOAD

= 100pF

Serial Clock Rising Edge to DOUT High-Z

chz

LOAD

= 100pF, Figure 2

Last Serial Clock to Next CNVST (Successive Conversions on CH0)

ccs

Note 1: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range and off-

set have been calibrated.

Note 2: Input = 0, with logic input levels of 0 and V

ELECTRICAL CHARACTERISTICS (continued)

(VDD= +2.7V to +3.6V (MAX1117), VDD= +4.5V to +5.5V (MAX1119), VDD= REF = +2.7V to +5.5V (MAX1118),TA= T

MIN

to T

MAX

unless otherwise noted.)

10 100

100 500

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power,

2-Channel, Serial 8-Bit ADCs

_______________________________________________________________________________________ 5

Typical Operating Characteristics (continued)

(VDD= +3V (MAX1117), VDD= +5V (MAX1119), VDD= V

REF

= +3V (MAX1118), f

SCLK

= 5MHz, f

SAMPLE

= 100ksps, C

LOAD

= 100pF,

TA = +25°C, unless otherwise noted.)

0.1

0.01 0.1 1 10 100

MAX1117/MAX1119

SUPPLY CURRENT vs. CONVERSION RATE

1.0

MAX1117/18/19 toc07

CONVERSION (ksps)

SUPPLY CURRENT (μA)

100.0

10.0

MAX1119 V

= +5V

MAX1117 V

= +3V

100

150

200

2.5 3.5 4.5 5.5

MAX1117/MAX1119 SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX1117/18/19 toc08

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (μA)

OUT

= 00000000

= V

DIGITAL INPUTS

MAX1117

MAX1119

100

150

200

-40 -15 3510 60 85

MAX1117/MAX1119

SUPPLY CURRENT vs. TEMPERATURE

MAX1117/18/19 toc09

TEMPERATURE (V)

SUPPLY CURRENT (μA)

OUT

= 00000000

= V

DIGITAL INPUTS

MAX1117 VDD = +3V

MAX1119 VDD = +5V

5.0

5.2

5.3

5.1

5.4

5.5

2.5 3.5 4.5 5.5

CONVERSION TIME

vs. SUPPLY VOLTAGE

MAX1117/18/19 toc11

SUPPLY VOLTAGE (V)

CONVERSION TIME (μs)

5.0

5.2

5.3

5.1

5.4

5.5

-40 -15 10 35 60 85

CONVERSION TIME vs. TEMPERATURE

MAX1117/18/19 toc12

TEMPERATURE (°C)

CONVERSION TIME (μs)

VDD = +3V

VDD = +5V

-120

-80

-100

-60

-40

-20

0 20k10k 30k 40k 50k

FFT PLOT

MAX1117/18/19 toc13

ANALOG INPUT FREQUENCY (Hz)

AMPLITUDE (dB)

-0.2

-0.4

0.2

0.4

2.5 4.53.5 5.5

MAX1118

GAIN ERROR vs. SUPPLY VOLTAGE

MAX1117/18/19 toc14

SUPPLY VOLTAGE (V)

GAIN ERROR (LSB)

REF

= 2.048V

-0.5

-0.2

-0.3

-0.4

-0.1

0.1

0.2

0.3

0.4

0.5

-40 10-15 356085

MAX1118

GAIN ERROR vs. TEMPERATURE

MAX1117/18/19 toc15

TEMPERATURE (°C)

GAIN ERROR (LSB)

VDD = +3V V

REF

= 2.048V

-1.0

-0.6

-0.4

-0.8

-0.2

14532

MAX1118

GAIN ERROR vs. REFERENCE VOLTAGE

MAX1117/18/19 toc16

REFERENCE VOLTAGE (V)

GAIN ERROR (LSB)

VDD = +5.5V

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VDD= +3V (MAX1117), VDD= +5V (MAX1119), VDD= V

REF

= +3V (MAX1118), f

SCLK

= 5MHz, f

SAMPLE

= 100ksps, C

LOAD

= 100pF,

TA = +25°C, unless otherwise noted.)

-0.5

-0.1

0.1

-0.2

-0.3

-0.4

0.3

0.2

0.4

0.5

2.5 3.0 4.0 5.04.53.5 5.5

MAX1118

OFFSET ERROR vs. SUPPLY VOLTAGE

MAX1117/18/19 toc17

SUPPLY VOLTAGE (V)

OFFSET ERROR (LSB)

REF

= 2.048V

-0.5

-0.1

0.1

-0.2

-0.3

-0.4

0.3

0.2

0.4

0.5

-40 35 6010-15 85

MAX1118

OFFSET ERROR vs. TEMPERATURE

MAX1117/18/19 toc18

TEMPERATURE (°C)

OFFSET ERROR (LSB)

VDD = +3V V

REF

= 2.048V

-0.5

-0.1

0.1

-0.3

0.3

-0.4

0.2

-0.2

0.4

0.5

14532

MAX1118

OFFSET ERROR vs. REFERENCE VOLTAGE

MAX1117/18/19 toc19

REFERENCE VOLTAGE (V)

OFFSET ERROR (LSB)

VDD = 5.5V

SUPPLY VOLTAGE (V)

0.6

0.8

0.4

0.2

1.2

1.0

1.4

2.5 4.53.5 5.5

MAX1117/MAX1119

GAIN ERROR vs. SUPPLY VOLTAGE

MAX1117/18/19 toc20

GAIN ERROR (%FSR)

MAX1119 V

= +5V

MAX1117 V

= +3V

-2.0

0.5

-1.0

-0.5

-1.5

1.5

1.0

2.0

-40 603510-15 85

MAX1117/MAX1119

GAIN ERROR vs. TEMPERATURE

MAX1117/18/19 toc21

TEMPERATURE (°C)

GAIN ERROR (%FSR)

MAX1116 V

= +5V

MAX1117 V

= +3V

-120

-80

-100

-60

-40

-20

0 20k10k 30k 40k 50k

FFT PLOT

MAX1117/18/19 toc22

ANALOG INPUT FREQUENCY (Hz)

AMPLITUDE (dB)

SAMPLE

= 100kHz

= 25.1kHz

= 0.9 x V

REFp-p

-0.5

-0.1

0.1

-0.2

-0.3

-0.4

0.3

0.2

0.4

0.5

2.5 3.0 4.0 5.04.53.5 5.5

MAX1117/MAX1119

OFFSET ERROR vs. SUPPLY VOLTAGE

MAX1117/18/19 toc23

SUPPLY VOLTAGE (V)

OFFSET ERROR (LSB)

MAX1117 VDD = +3V

MAX1119 VDD = +5V

-0.5

-0.1

0.1

-0.2

-0.3

-0.4

0.3

0.2

0.4

0.5

-40 -15 603510 85

MAX1117/MAX1119

OFFSET ERROR vs. TEMPERATURE

MAX1117/18/19 toc24

TEMPERATURE (°C)

OFFSET ERROR (LSB)

MAX1117 VDD = +3V

MAX1119 VDD = +5V

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power,

2-Channel, Serial 8-Bit ADCs

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(VDD= +3V (MAX1117), VDD= +5V (MAX1119), VDD= V

REF

= +3V (MAX1118), f

SCLK

= 5MHz, f

SAMPLE

= 100ksps, C

LOAD

= 100pF,

TA = +25°C, unless otherwise noted.)

10.5%

7.0%

3.5%

17.5%

21.0%

14.0%

3.980 4.020 4.1404.1004.060 4.180

REFERENCE VOLTAGE vs.

NUMBER OF PIECES

MAX1115 toc25

REFERENCE VOLTAGE (V)

10.5%

7.0%

3.5%

17.5%

21.0%

14.0%

1.982 2.008 2.0862.0602.034 2.112

REFERENCE VOLTAGE vs.

NUMBER OF PIECES

MAX1117/18/19 toc26

REFERENCE VOLTAGE (V)

Pin Description

PIN NAME FUNCTION

1VDDPositive Supply Voltage

2 CH0 CH0 Analog Voltage Input

3 CH1 CH1 Analog Voltage Input

4 GND Ground

Internally Connected. Connect to ground. (Reference Input, MAX1118 only.)

6 CNVST Convert/Start Input. CNVST initiates a power-up and starts a conversion on its falling edge.

7DOUT

Serial Data Output. Data is clocked out on the falling edge of SCLK. DOUT goes low at the start of a conversion and presents the MSB at the completion of a conversion. DOUT goes high impedance once data has been fully clocked out.

8 SCLK Serial Clock. Used for clocking out data on DOUT.

I.C.(REF)

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs

8 _______________________________________________________________________________________

I/O

SCK (SK)

MISO (SI)

GND

DOUT

SCLK

CNVST

GND

0.1μF

1μF

CH0

REF*

* MAX1118 ONLY

1μF

ANALOG

INPUTS

MAX1117 MAX1118 MAX1119

CPU

CH1

Figure 3. Typical Operating Circuit

GND

HOLD

CAPACITIVE DAC

COMPARATOR

16pF

6.5kΩ

AUTOZERO

RAIL

TRACK

HOLD

CH0

CH1

Figure 4. Equivalent Input Circuit

Detailed Description

The MAX1117/MAX1118/MAX1119 ADCs use a successive-approximation conversion technique and input T/H circuitry to convert an analog signal to an 8-bit digital output. The SPI/QSPI/MICROWIRE compatible interface directly connects to microprocessors (µPs) without additional circuity (Figure 3).

Track/Hold

The input architecture of the ADC is illustrated in Figure 4’s equivalent-input circuit and is composed of the T/H, the input multiplexer, the input comparator, the switched capacitor DAC, and the auto-zero rail.

The acquisition interval begins with the falling edge of CNVST. During the acquisition interval, the analog

inputs (CH0, CH1) are connected to the holding capacitor (C

HOLD

). Once the acquisition has completed, the

T/H switch opens and C

HOLD

is connected to GND,

retaining the charge on C

HOLD

as a sample of the sig-

nal at the analog input.

Sufficiently low source impedance is required to ensure an accurate sample. A source impedance <1.5kΩ is recommended for accurate sample settling. A 100pF capacitor at the ADC inputs will also improve the accuracy of an input sample.

Conversion Process

The MAX1117/MAX1118/MAX1119 conversion process is internally timed. The total acquisition and conversion process takes <7.5µs. Once an input sample has been acquired, the comparator’s negative input is then con-

3kΩ

LOAD

GND

DOUT

LOAD

GND

3kΩ

DOUT

a) V

TO V

b) HIGH-Z to VOL AND VOH to V

Figure 1. Load Circuits for Enable Time

Figure 2. Load Circuits for Disable Time

DOUT

3kΩ

DOUT

LOAD

GND

TO HIGH-Z b) VOL TO HIGH-Z

a) V

3kΩ

GND

LOAD

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power,

2-Channel, Serial 8-Bit ADCs

_______________________________________________________________________________________ 9

nected to an autozero supply. Since the device requires only a single supply, the negative input of the comparator is set to equal VDD/2. The capacitive DAC restores the positive input to VDD/2 within the limits of 8bit resolution. This action is equivalent to transferring a charge QIN= 16pF x VINfrom C

HOLD

to the binaryweighted capacitive DAC, which in turn forms a digital representation of the analog-input signal.

Input Voltage Range

Internal protection diodes that clamp the analog input to VDDand GND allow the input pins (CH0, CH1) to swing from (GND - 0.3V) to (VDD+ 0.3V) without damage. However, for accurate conversions, the inputs must not exceed (VDD+ 50mV) or be less than (GND 50mV).

Input Bandwidth

The ADC’s input tracking circuitry has a 4MHz smallsignal bandwidth, so it is possible to digitize highspeed transient events and measure periodic signals with bandwidths exceeding the ADC’s sampling rate by using undersampling techniques. To avoid high-frequency signals being aliased into the frequency band of interest, anti-alias filtering is recommended.

Serial Interface

The MAX1117/MAX1118/MAX1119 have a 3-wire serial interface. The CNVST and SCLK inputs are used to control the device, while the three-state DOUT pin is used to access the conversion results.

The serial interface provides connection to microcontrollers (µCs) with SPI, QSPI, and MICROWIRE serial interfaces at clock rates up to 5MHz. The interface supports either an idle high or low SCLK format. For SPI and QSPI, set CPOL = CPHA = 0 or CPOL = CPHA = 1 in the SPI control registers of the µC. Figure 5 shows the MAX1117/MAX1118/MAX1119 common serial-interface connections. See Figures 6a–6d for details on the serial interface timing and protocol.

Digital Inputs and Outputs

The MAX1117/MAX1118/MAX1119 perform conversions using an internal clock. This frees the µP from the burden of running the SAR conversion clock and allows the conversion results to be read back at the µP’s convenience at any clock rate up to 5MHz.

The acquisition interval begins with the falling edge of CNVST. CNVST can idle between conversions in either a high or low state. If idled in a low state, CNVST must

be brought high for at least 50ns, then brought low to initiate a conversion. To select CH1 for conversion, the CNVST pin must be brought high and low for a second time (Figures 6c and 6d).

After CNVST is brought low, allow 7.5μs for the conversion to be completed. While the internal conversion is in progress, DOUT is low. The MSB is present at the DOUT pin immediately after conversion is completed. The conversion result is clocked out at the DOUT pin and is coded in straight binary (Figure 7). Data is clocked out at SCLK’s falling edge in MSB-first format at rates up to 5MHz. Once all data bits are clocked out, DOUT goes high impedance (100ns to 500ns after the rising edge) of the eighth SCLK pulse.

CNVST

SCLK

DOUT

I/O

SCK

MISO

+3V

a) SPI

CNVST

SCLK

DOUT

SCK

MISO

+3V

b) QSPI

MAX1117 MAX1118 MAX1119

SCLK

DOUT

I/O

c) MICROWIRE

Figure 5. Common Serial-Interface Connections

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs

10 ______________________________________________________________________________________

During the conversion process, SCLK is ignored. Only after a conversion is complete will SCLK cause serial data to be output. Falling edges on CNVST, during an active conversion process, interrupt the current conversion and cause the input multiplexer to switch to CH1. To reinitiate a conversion on CH0, it is necessary to

allow for a conversion to be complete and all of the data to be read out. Once a conversion has been completed, the MAX1117/MAX1118/MAX1119 will go into AutoShutdown™ mode (<1µA typ) until the next conversion is initiated.

ACTIVE POWER-DOWN MODE

CNVST

SCLK

DOUT

CH0

IDLE LOW IDLE LOW

CH0

csh

conv

ccs

chz

D7 (MSB) D6 D5 D4 D3 D2 D1 D0

csd

Figure 6a. Conversion and Interface Timing, Conversion on CH0 with SCLK Idle Low

ACTIVE POWER-DOWN MODE

CNVST

SCLK

DOUT

CH0

IDLE HIGH

CH0

csh

conv

ccs

chz

D7 (MSB) D6 D5 D4 D3 D2 D1 D0

csd

Figure 6b. Conversion and Interface Timing, Conversion on CH0 with SCLK Idle High

AutoShutdown is a trademark of Maxim Integrated Products.

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power,

2-Channel, Serial 8-Bit ADCs

______________________________________________________________________________________ 11

ACTIVE POWER-DOWN MODE

CNVST

SCLK

OUT

CH0

IDLE LOW IDLE LOW

CH0 CH1CH1

csh

conv

ccs

csl

chz

D7 (MSB) D6 D5 D4 D3 D2 D1 D0

csd

Figure 6c. Conversion and Interface Timing, Conversion on CH1 with SCLK Idle Low

ACTIVE POWER-DOWN MODE

CNVST

SCLK

OUT

CH0

IDLE HIGHIDLE HIGH

CH0 CH1CH1

csh

conv

ccs

csl

chz

D7 (MSB) D6 D5 D4 D3 D2 D1 D0

csd

Figure 6d. Conversion and Interface Timing, Conversion on CH1 with SCLK Idle High

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs

12 ______________________________________________________________________________________

Applications Information

Power-On Reset

When power is first applied, the MAX1117/MAX1118/ MAX1119 are in AutoShutdown state (<1μA typ). A conversion can be started by toggling CNVST high to low. Powering up the MAX1117/MAX1118/MAX1119 with CNVST low will not start a conversion. Conversions initiated prior to the external reference settling (MAX1118) will result in errors. Thus, it is necessary to allow the external reference to stabilize prior to initiating a conversion.

AutoShutDown and Supply Current

Requirements

The MAX1117/MAX1118/MAX1119 are designed to automatically shutdown once a conversion is complete without any external control. An input sample and conversion process will typically take 5µs to complete, during which time the supply current to the analog sections of the device is fully on. All analog circuitry is shutdown after a conversion completes, which results in a supply current of <1µA (see Shutdown Current vs. Supply Voltage Plot in the Typical Operating Characteristics). The digital conversion result is maintained in a static register and is available for access through the serial interface at any time.

The power consumption consequence of this architecture is dramatic when relatively slow conversion rates are needed. For example, at a conversion rate of 10ksps, the average supply current for the MAX1117 is

15µA, while at 1ksps it drops to 1.5µA and at 0.1ksps it is just 0.3µA, or a miniscule 1µW of power consumption (see Average Supply Current vs. Conversion Rate Plot in the Typical Operating Characteristics).

External Voltage Reference (MAX1118)

Connect an external reference between +1V and V

at the REF pin. The DC input impedance at REF is extremely high, consisting of leakage current only (10nA typ). During a conversion, the reference must be able to deliver up to 20µA average load current and have an output impedance of 100Ω or less. If the refer- ence has higher output impedance or is noisy, bypass it close to the REF pin with a 10nF or larger capacitor.

Transfer Function

Figure 7 depicts the input/output transfer function. Output coding is binary with a +2.048V reference 1LSB = 8mV (V

REF

/256).

Layout, Grounding, Bypassing

For best performance, the board layout should ensure that digital and analog signal lines are separated from each other. Do not run analog and digital (especially clock) lines parallel to one another or run digital lines underneath the ADC package.

Figure 8 shows the recommended system-ground connections. A single-point analog ground (star-ground point) should be established at the ADC ground. Connect all analog grounds to the star ground. The ground return to the power supply for the star ground

OUTPUT CODE

FULL-SCALE

TRANSITION

11111111

11111110

11111101

00000011

00000010

00000001

00000000

123

FS - 1 1/2 LSB

FS = V

REF

1LSB = V

REF

256

INPUT VOLTAGE (LSB)

Figure 7. Input/Output Transfer Function

GND

+3V/+5V

SYSTEM POWER SUPPLIES

DGNDV

1μF

10Ω*

0.1μF

GND

*OPTIONAL

DIGITAL

CIRCUITRY

MAX1117 MAX1118 MAX1119

Figure 8. Power-Supply Connections

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power,

2-Channel, Serial 8-Bit ADCs

______________________________________________________________________________________ 13

should be low impedance and as short as possible for noise-free operation.

High-frequency noise in the VDDpower supply may affect the comparator in the ADC. Bypass the supply to the star ground with a 0.1µF capacitor close to the V

pin of the MAX1117/MAX1118/MAX1119. Minimize capacitor lead lengths for best supply-noise rejection. If the power supply is noisy, a 1µF capacitor in conjunction with a 10Ω series resistor can be connected to form a lowpass filter.

Chip Information

TRANSISTOR COUNT: 2000

PROCESS: BiCMOS

INPUT

MULTIPLEXER

SCLK

CNVST

CH0

INPUT

TRACK

AND HOLD

INTERNAL

REFERENCE

+2.096V

OR +4.096V

8-BIT

SAR ADC

OUTPUT

SHIFT

OUT

CONTROL

LOGIC AND

INTERNAL

OCSILLATOR

MAX1117 MAX1119

CH1

GND

Functional Diagrams

MAX1117/MAX1118/MAX1119

Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages

MARKING

SOT23, 8L.EPS

PACKAGE OUTLINE, SOT-23, 8L BODY

21-0078 G

MAXIM MAX1117, MAX1118, MAX1119 Technical data

Specifications and Main Features

Frequently Asked Questions

User Manual