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MAX186/MAX188

Low-Power, 8-Channel,

Serial 12-Bit ADCs

For pricing, delivery, and ordering information, please contact Maxim Direct at

1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

EVALUATION KIT AVAILABLE

General Description

The MAX186/MAX188 are 12-bit data-acquisition sys-

tems that combine an 8-channel multiplexer, high-

bandwidth track/hold, and serial interface together with

high conversion speed and ultra-low power consump-

tion. The devices operate with a single +5V supply or

dual ±5V supplies. The analog inputs are software con-

figurable for unipolar/bipolar and single-ended/differen-

tial operation.

The 4-wire serial interface directly connects to SPI,

QSPI™ and MICROWIRE

devices without external

logic. A serial strobe output allows direct connection to

TMS320 family digital signal processors. The

MAX186/MAX188 use either the internal clock or an

external serial-interface clock to perform successive-

approximation A/D conversions. The serial interface can

operate beyond 4MHz when the internal clock is used.

The MAX186 has an internal 4.096V reference while the

MAX188 requires an external reference. Both parts have

a reference-buffer amplifier that simplifies gain trim .

The MAX186/MAX188 provide a hard-wired SHDN pin

and two software-selectable power-down modes.

Accessing the serial interface automatically powers up

the devices, and the quick turn-on time allows the

MAX186/MAX188 to be shut down between every con-

version. Using this technique of powering down

between conversions, supply current can be cut to

under 10µA at reduced sampling rates.

The MAX186/MAX188 are available in 20-pin PDIP and

SO packages, and in a shrink small-outline package

(SSOP), that occupies 30% less area than an 8-pin

PDIP. For applications that call for a parallel interface,

see the MAX180/MAX181 data sheet. For anti-aliasing

filters, consult the MAX274/MAX275 data sheet.

________________________Applications

Portable Data Logging

Data-Acquisition

High-Accuracy Process Control

Automatic Testing

Robotics

Battery-Powered Instruments

Medical Instruments

____________________________Features

o 8-Channel Single-Ended or 4-Channel

Differential Inputs

o Single +5V or ±5V Operation

o Low Power: 1.5mA (Operating Mode)

2µA (Power-Down Mode)

o Internal Track/Hold, 133kHz Sampling Rate

o Internal 4.096V Reference (MAX186)

o SPI-/QSPI-/MICROWIRE-/TMS320-Compatible

4-Wire Serial Interface

o Software-Configurable Unipolar or Bipolar Inputs

o 20-Pin PDIP, SO, SSOP Packages

o Evaluation Kit Available

Ordering Information

TOP VIEW

PDIP/SO/SSOP

SCLK

DIN

SSTRB

DOUT

DGND

AGND

REFADJ

VREFSHDN

CH7

CH6

CH5

CH4

CH3

CH2

CH1

CH0

MAX186

MAX188

____________________Pin Configuration

QSPI is a trademark of Motorola.

MICROWIRE is a registered trademark of National

Semiconductor.

19-0123; Rev 5; 1/12

Ordering Information continued on last page.

†

Parts are offered in grades A, B, C and D (grades defined in

Electrical Characteristics). When ordering, please specify grade.

Contact factory for availability of A-grade in SSOP package.

Dice are specified at +25°C, DC parameters only.

Denotes a lead(Pb)-free/RoHS-compliant package.

PART

†

TEMP RANGE PIN-PACKAGE

MAX186_CPP+ 0°C to +70°C 20 PDIP

MAX186_CWP+ 0°C to +70°C 20 SO

MAX186_CAP+ 0°C to +70°C 20 SSOP

MAX186DC/D 0°C to +70°C Dice*

MAX186_EPP+ -40°C to +85°C 20 PDIP

MAX186_EWP+ -40°C to +85°C 20 SO

MAX186_EAP+ -40°C to +85°C 20 SSOP

Summary of content (25 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs General Description The MAX186/MAX188 are 12-bit data-acquisition systems that combine an 8-channel multiplexer, highbandwidth track/hold, and serial interface together with high conversion speed and ultra-low power consumption. The devices operate with a single +5V supply or dual ±5V supplies. The analog inputs are software configurable for unipolar/bipolar and single-ended/differential operation.
PAGE 2
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs ABSOLUTE MAXIMUM RATINGS VDD to AGND............................................................-0.3V to +6V VSS to AGND ............................................................+0.3V to -6V VDD to VSS ..............................................................-0.3V to +12V AGND to DGND.....................................................-0.3V to +0.3V CH0–CH7 to AGND, DGND .............(VSS - 0.3V) to (VDD + 0.3V) CH0–CH7 Total Input Current.....
PAGE 3
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs ELECTRICAL CHARACTERISTICS (continued) (VDD = 5V ±5%; VSS = 0V or -5V; fCLK = 2.0MHz, external clock (50% duty cycle); 15 clocks/conversion cycle (133ksps); MAX186— 4.7µF capacitor at VREF pin; MAX188—external reference, VREF = 4.096V applied to VREF pin; TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL Small-Signal Bandwidth CONDITIONS MIN -3dB rolloff Full-Power Bandwidth TYP MAX UNITS 4.
PAGE 4
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs ELECTRICAL CHARACTERISTICS (continued) (VDD = 5V ±5%; VSS = 0V or -5V; fCLK = 2.0MHz, external clock (50% duty cycle); 15 clocks/conversion cycle (133ksps); MAX186— 4.7µF capacitor at VREF pin; MAX188—external reference, VREF = 4.096V applied to VREF pin; TA = TMIN to TMAX, unless otherwise noted.
PAGE 5
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs ELECTRICAL CHARACTERISTICS (continued) (VDD = 5V ±5%; VSS = 0V or -5V; fCLK = 2.0MHz, external clock (50% duty cycle); 15 clocks/conversion cycle (133ksps); MAX186— 4.7µF capacitor at VREF pin; MAX188—external reference, VREF = 4.096V applied to VREF pin; TA = TMIN to TMAX, unless otherwise noted.
PAGE 6
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs __________________________________________Typical Operating Characteristics POWER-SUPPLY REJECTION vs. TEMPERATURE CHANNEL-TO-CHANNEL OFFSET MATCHING vs. TEMPERATURE INTERNAL REFERENCE VOLTAGE vs. TEMPERATURE 0.16 0.30 VDD = +5V ±5% 0.25 2.456 OFFSET MATCHING (LSBs) 0.20 2.455 VREFADJ (V) PSR (LSBs) 0.14 VSS = 0V or -5V 0.15 0.10 2.454 2.453 0.05 0.00 0.10 0.08 0.06 0.04 0.02 2.452 -0.
PAGE 7
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs ________________________________________________Pin Description (continued) PIN NAME 12 REFADJ FUNCTION Input to the Reference-Buffer Amplifier. To disable the reference-buffer amplifier, connect REFADJ to VDD. 13 AGND Analog Ground. Also IN- Input for single-ended conversions. 14 DGND Digital Ground 15 DOUT Serial Data Output. Data is clocked out at the falling edge of SCLK. High impedance when CS is high. 16 SSTRB Serial Strobe Output.
PAGE 8
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs _______________Detailed Description The MAX186/MAX188 use a successive-approximation conversion technique and input track/hold (T/H) circuitry to convert an analog signal to a 12-bit digital output. A flexible serial interface provides easy interface to microprocessors. No external hold capacitors are required. Figure 3 shows the block diagram for the MAX186/MAX188.
PAGE 9
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs VDD +5V OSCILLOSCOPE 0.1µF DGND AGND 0V TO 4.096V ANALOG 0.01µF INPUT CH7 SCLK VSS MAX186 MAX188 SSTRB CS DOUT* SCLK +5V DIN +5V CH1 CH2 CH3 CH4 DOUT D1 1N4148 C2 0.01µF 2MHz OSCILLATOR REFADJ SSTRB VREF SHDN N.C. C1 4.7µF +2.5V +2.5V REFERENCE ** * FULL-SCALE ANALOG INPUT, CONVERSION RESULT = $FFF (HEX) **REQUIRED FOR MAX188 ONLY. A POTENTIOMETER MAY BE USED IN PLACE OF THE REFERENCE FOR TEST PURPOSES. Figure 5.
PAGE 10
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs single-ended unipolar conversions on CH7 in external clock mode without powering down between conversions. In external clock mode, the SSTRB output pulses high for one clock period before the most significant bit of the 12-bit conversion result comes out of DOUT. Varying the analog input to CH7 should alter the sequence of bits from DOUT. A total of 15 clock cycles is required per conversion.
PAGE 11
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs DIFF = 1) Table 3. Channel Selection in Single-Ended Mode (SGL/D SEL2 SEL1 SEL0 CH0 0 0 0 + 1 0 0 0 0 1 1 0 1 0 1 0 1 1 0 0 1 1 1 1 1 CH1 CH2 CH3 CH4 CH5 CH6 CH7 AGND – + – + – + – + – + – + – + – DIFF = 0) Table 4.
PAGE 12
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs CS tACQ SCLK 1 4 8 START SEL2 SEL1 SEL0 UNI/ BIP DIN SCL/ PD1 DIFF 12 16 20 24 PD0 RB3 RB2 SSTRB RB1 B11 MSB DOUT B9 B8 ACQUISITION IDLE A/D STATE B10 B7 B6 B5 B4 B3 B2 B1 CONVERSION B0 LSB FILLED WITH ZEROS IDLE 1.5μs (CLK = 2MHz) Figure 6. 24-Bit External Clock Mode Conversion Timing (SPI, QSPI and Microwire Compatible) ••• CS tCSH tCSS tCL tCH SCLK tCSH ••• tDS tDH ••• DIN tDV tDO tTR ••• DOUT Figure 7.
PAGE 13
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs ••• CS ••• tSTR tSDV SSTRB ••• ••• tSSTRB SCLK tSSTRB •••• ••• • PD0 CLOCKED IN Figure 8. External Clock Mode SSTRB Detailed Timing CS SCLK DIN 1 2 3 4 5 START SEL2 SEL1 SEL0 UNI/ DIP 7 8 SCL/ PD1 DIFF PD0 6 9 10 11 12 18 19 20 21 22 23 24 SSTRB tCONV B11 MSB DOUT A/D STATE IDLE ACQUISITION CONVERSION 10μs MAX B10 B9 B2 B1 B0 LSB FILLED WITH ZEROS IDLE 1.5μs (CLK = 2MHz) Figure 9.
PAGE 14
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs CS • • • tCONV tCSS tSCK tCSH SSTRB • • • tSSTRB SCLK • • • PD0 CLOCK IN NOTE: FOR BEST NOISE PERFORMANCE, KEEP SCLK LOW DURING CONVERSION. Figure 10. Internal Clock Mode SSTRB Detailed Timing Data Framing The falling edge of CS does not start a conversion on the MAX186/MAX188. The first logic high clocked into DIN is interpreted as a start bit and defines the first bit of the control byte.
PAGE 15
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs CS 1 8 1 8 1 SCLK S DIN S CONTROL BYTE 0 CONTROL BYTE 1 CONTROL BYTE 2 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 DOUT S CONVERSION RESULT 1 CONVERSION RESULT 0 SSTRB Figure 11a.
PAGE 16
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs CLOCK MODE INTERNAL EXTERNAL EXTERNAL SHDN SETS FAST POWER-DOWN MODE SETS EXTERNAL CLOCK MODE DIN S X X X X X 1 1 S X X X X X 0 1 DOUT DATA VALID (12 DATA BITS) MODE POWERED UP SETS EXTERNAL CLOCK MODE S X X X X X 1 1 DATA VALID (12 DATA BITS) VALID DATA INVALID FAST POWER-DOWN POWERED UP FULL POWER DOWN POWERED UP Figure 12a. Timing Diagram Power-Down Modes, External Clock Table 5.
PAGE 17
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs CLOCK MODE INTERNAL CLOCK MODE SETS FULL POWER-DOWN SETS INTERNAL CLOCK MODE DIN S X X X X X 1 0 S X X X X X 0 0 DOUT S DATA VALID DATA VALID CONVERSION SSTRB CONVERSION FULL POWER-DOWN POWERED UP MODE POWERED UP Figure 12b. Timing Diagram Power-Down Modes, Internal Clock Hardware Power-Down The SHDN pin places the converter into the full power-down mode. Unlike with the software shut-down modes, conversion is not completed.
PAGE 18
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs MAX186/MAX188 FAST POWER-DOWN 2ms FASTPD WAIT 400kHz EXTERNAL CLOCK INTERNAL COMPENSATION 8 CHANNELS 100 1 CHANNEL 10 1 10,000 AVG. SUPPLY CURRENT (µA) AVG. SUPPLY CURRENT (µA) 1000 MAX186-14A MAX186 FULL POWER-DOWN 8 CHANNELS 1000 1 CHANNEL 100 2MHz EXTERNAL CLOCK EXTERNAL COMPENSATION 50µs WAIT 10 0 50 100 150 200 250 300 350 400 450 500 0 2k CONVERSIONS PER CHANNEL PER SECOND Figure 14a. MAX186 Supply Current vs.
PAGE 19
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs OUTPUT CODE FULL-SCALE TRANSITION 11 . . . 111 011 . . . 111 011 . . . 110 11 . . . 110 FS = +4.096 2 1LSB = +4.096 4096 11 . . . 101 000 . . . 010 000 . . . 001 FS = +4.096V 1LSB = FS 4096 000 . . . 000 111 . . . 111 111 . . . 110 111 . . . 101 00 . . . 011 00 . . . 010 100 . . . 001 00 . . . 001 100 . . . 000 00 . . . 000 0 1 2 3 0V -FS FS +FS - 1LSB INPUT VOLTAGE (LSBs) INPUT VOLTAGE (LSBs) FS - 3/2LSB Figure 15.
PAGE 20
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs High-Speed Digital Interfacing with QSPI The MAX186/MAX188 can interface with QSPI at high throughput rates using the circuit in Figure 19. This QSPI circuit can be programmed to do a conversion on each of the eight channels. The result is stored in memory without taxing the CPU since QSPI incorporates its own micro-sequencer.
PAGE 21
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs *Title : MAX186.ASM * Description : * This is a shell program for using a stand-alone 68HC16 without any external memory. The internal 1K RAM * is put into bank $0F to maintain 68HC11 code compatibility. This program was written with software * provided in the Motorola 68HC16 Evaluation Kit. * * Roger J.A.
PAGE 22
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs ;set delay between transfers LDD #$0800 STD SPCR2 ;set ENDQP to $8 for 9 transfers ***** Initialize QSPI Command RAM ***** LDAA #$80 ;CONT=1,BITSE=0,DT=0,DSCK=0,PCS0=ACTIVE STAA $FD40 ;store first byte in COMMAND RAM LDAA #$C0 ;CONT=1,BITSE=1,DT=0,DSCK=0,PCS0=ACTIVE STAA $FD41 STAA $FD42 STAA $FD43 STAA $FD44 STAA $FD45 STAA $FD46 STAA $FD47 LDAA #$40 ;CONT=0,BITSE=1,DT=0,DSCK=0,PCS0=ACTIVE STAA $FD48 ***** Initialize QSPI Transmit RAM ***** LDD #$008F
PAGE 23
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs CS •••• •••• SCLK •••• SSTRB DIN •••• Figure 21. QSPI Assembly-Code Timing TMS320C3x to MAX186 Interface Figure 22 shows an application circuit to interface the MAX186/MAX188 to the TMS320 in external clock mode. The timing diagram for this interface circuit is shown in Figure 23.
PAGE 24
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs CS SCLK DIN START SEL2 SEL1 SEL0 UNI/BIP SGL/DIF PD1 PD0 HIGH IMPEDANCE SSTRB DOUT MSB B10 B1 HIGH IMPEDANCE LSB Figure 23. TMS320 Serial Interface Timing Diagram __________Typical Operating Circuit _Ordering Information (continued) PART† +5V CH0 0V to 4.096V ANALOG INPUTS DGND AGND CH7 MAX186 C1 4.7μF C2 0.01μF C4 0.1μF CPU I/O SCLK SCK (SK)* DIN MOSI (SO) DOUT REFADJ C3 0.
PAGE 25
MAX186/MAX188 Low-Power, 8-Channel, Serial 12-Bit ADCs Revision History REVISION NUMBER REVISION DATE 0 3/93 Initial release 5 1/12 Updated the Ordering Information and Electrical Characteristics. DESCRIPTION PAGES CHANGED — 1, 3, 18 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied.