Maxim MAX1299AEAE 12-bit serial-output temperature sensors with 5-channel adc Datasheet

19-1726; Rev 0; 5/00
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
The MAX1298/MAX1299 implement local and remote
temperature sensing with 12-bit resolution, using +5V
and +3V supply voltages, respectively. Accuracy is
±1°C from 0 to +70°C, with no calibration needed. The
devices feature an algorithmic switched-capacitor analog-to-digital converter (ADC), an on-chip clock, and a
3-wire serial interface compatible with SPI™, QSPI™,
and MICROWIRE™.
The MAX1298/MAX1299 also perform fully differential
voltage measurements with 12-bit resolution and separate track-and-hold (T/H) for positive and negative
inputs. Both devices accept versatile input modes consisting of two 3-channel signal pairs, five 1-channel signals relative to a floating common, or VDD/4 relative to
ground. An external reference may be used for more
accurate voltage measurements.
Typical power consumption is only 1.3mW (MAX1299).
A shutdown mode and two standby modes provide
multiple strategies for prolonging battery life in portable
applications that require limited sampling throughput.
Features
♦ Local and Remote Temperature Sensing
♦ 12-Bit Resolution for Temperature and Voltage
Inputs
♦ ±1°C Accuracy from -40°C to +85°C
♦ Fully Differential Inputs
♦ Single-Supply Operation
+4.75V to +5.25V (MAX1298)
+2.7V to +3.6V (MAX1299)
♦ 3-Wire SPI/QSPI/MICROWIRE-Compatible
Interface
♦ Internal Precision Voltage Reference
2.50V (MAX1298)
1.20V (MAX1299)
♦ Space-Saving 16-Pin SSOP Package
Ordering Information
The MAX1298/MAX1299 are available in 16-pin SSOP
packages.
________________________Applications
Temperature/Voltage Supervision of
Workstations and Communications Equipment
Hand-Held Instruments
Medical Equipment
Industrial Process Control
PART
TEMP. SENSE
PINACCURACY
PACKAGE
(°C)
TEMP.
RANGE
MAX1298AEAE -40°C to +85°C
16 SSOP
±0.75
MAX1298BEAE* -40°C to +85°C
16 SSOP
±1.0
MAX1298CEAE -40°C to +85°C
MAX1299AEAE -40°C to +85°C
16 SSOP
±4.0
16 SSOP
±0.75
MAX1299BEAE* -40°C to +85°C
16 SSOP
±1.0
MAX1299CEAE -40°C to +85°C 16 SSOP
*Future product—contact factory for availability.
±4.0
Pin Configuration
TOP VIEW
AIN1 1
16 AIN0
SHO 2
15 AIN5
AIN2 3
14 REF
AIN3 4
AIN4 5
MAX1298
MAX1299
GND 6
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
12 VDD
11 SCLK
10 DIN
SSTRB 7
Typical Operating Circuit appears at end of data sheet.
13 GND
9
CS 8
DOUT
SSOP
________________________________________________________________ Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX1298/MAX1299
General Description
MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
ABSOLUTE MAXIMUM RATINGS
VDD to GND.……………………………………………-0.3V to +6V
SHO to GND ...............................................-0.3V to (VDD + 0.3V)
Analog Inputs to GND
(AIN0, AIN1, AIN2, AIN3, AIN4,
AIN5, REF).............................................-0.3V to (VDD + 0.3V)
Digital Inputs to GND (DIN, SCLK, CS)......-0.3V to (VDD + 0.3V)
Digital Outputs to GND (DOUT, SSTRB) ....-0.3V to (VDD + 0.3V)
Digital Output Sink Current ..…………………………………25mA
Maximum Current into Any Pin……………………………….50mA
Continuous Power Dissipation (TA = +70°C)
16-Pin SSOP (derate 8.00mW/°C above +70°C) ........667mW
Operating Temperature Range
MAX129_ _EAE ...............................................-40°C to +85°C
Junction Temperature....……………………………………+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) ....……………………+300°C
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.
ELECTRICAL CHARACTERISTICS
(VDD = 4.75V to 5.25V (MAX1298), VDD = +2.7V to 3.6V (MAX1299), external reference, VREF = +2.5V (MAX1298), VREF = +1.2V
(MAX1299), fSCLK = 2.5MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC ACCURACY (Note 1)
Resolution
RES
Relative Accuracy (Note 2)
INL
±1
LSB
Differential Nonlinearity
DNL
±1
LSB
Offset Error
12
Bits
±2
Inputs AIN0−AIN5
±10
Offset Temperature Coefficient
Gain Error
Inputs AIN0−AIN5, offset nulled
VDD /4 Absolute Error
Gain Temperature Coefficient
Channel-to-Channel Offset
Matching
LSB
µV/°C
±4
LSB
±2
LSB
±2
ppm/ °C
±0.5
LSB
CONVERSION RATE
Conversion Time (Note 3)
tCONV
Track/Hold Acquisition Time
tACQ
Aperture Delay
tAPR
Internal Clock Frequency
fCLK
Voltage measurement
1.1
Temperature measurement
2.2
µs
16
30
57.6
62.3
ms
ns
65.5
kHz
-2V REF
+2V REF
V
0
VDD
V
5
µA
ANALOG INPUTS (AIN0−AIN5)
Input Voltage Range (Note 4)
Common-Mode Range
Measurement with respect to IN-, Figure 1
Input Current (Note 5)
0.1
Input Capacitance
16
2
_______________________________________________________________________________________
pF
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
(VDD = 4.75V to 5.25V (MAX1298), VDD = +2.7V to 3.6V (MAX1299), external reference, VREF = +2.5V (MAX1298), VREF = +1.2V
(MAX1299), fSCLK = 2.5MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
0.8
V
DIGITAL INPUTS
Input Voltage Low
VIL
Input Voltage High
VIH
Input Hysteresis
VDD - 0.8
VHYST
Input Leakage Current
V
0.2
IIN
V
1
Input Capacitance
16
µA
pF
V
DIGITAL OUTPUTS
Output Low Voltage
Output High Voltage
VOL
VOH
Three-State Output Leakage
Current
IOUT
ISINK = 5mA
ISOURCE = 0.5mA
0.6
V
V
±10
µA
VDD - 0.6
Three-State Output
Capacitance
15
pF
POWER REQUIREMENTS
Positive Supply Voltage
Positive Supply Current (Note 6)
VDD
IDD
MAX1298
4.75
5.25
MAX1299
2.7
3.6
Full-on, voltage measurements,
internal reference
MAX1298
390
MAX1299
350
Full-on, voltage measurements,
external reference
MAX1298
310
MAX1299
280
Full-on, temperature measurements, internal reference
Full-on, temperature measurements, external reference
MAX1298
440
500
MAX1299
400
500
MAX1298
360
MAX1299
330
120
190
2
Standby, SCLK = GND
Standby-plus, SCLK = GND
Shutdown, SCLK = GND
Power-Supply Rejection Ratio
PSRR
(Note 7)
INTERNAL VOLTAGE REFERENCE CHARACTERISTICS
VDD = 5V
Reference Voltage
VREF
VDD = 3V
Reference Tempco
65
MAX1298
2.494
2.50
2.506
MAX1299
1.197
1.20
1.203
REF Line Regulation
REF Load Regulation
0 to 100µA output current
(Note 8)
mA
µF
0.1
fN = 10Hz to 10kHz
V
ppm/°C
1.25
Capacitive Bypass at REF
REF Output Noise
dB
±20
Output Short-Circuit Current
µA
10
50
TC VREF
V
MAX1298
130
MAX1299
65
µVRMS
MAX1298
+3.0
MAX1299
+0.2
MAX1298
4
10
MAX1299
2
10
mV/V
µV/µA
_______________________________________________________________________________________
3
MAX1298/MAX1299
ELECTRICAL CHARACTERISTICS (continued)
MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
ELECTRICAL CHARACTERISTICS (continued)
(VDD = 4.75V to 5.25V (MAX1298), VDD = +2.7V to 3.6V (MAX1299), external reference, VREF = +2.5V (MAX1298), VREF = +1.2V
(MAX1299), fSCLK = 2.5MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
EXTERNAL VOLTAGE REFERENCE CHARACTERISTICS
MAX1298
Reference Voltage Range
VREF
MAX1299
REF Input Resistance
CONDITIONS
MIN
TYP
0.8
2.5
0.8
1.2
Converting
10
Shutdown
25
REF Input Capacitance
MAX
UNITS
V
MΩ
24
pF
INTERNAL TEMPERATURE MEASUREMENT CHARACTERISTICS
Resolution
TA = +85°C, P D = 1mW
TA = 0°C to +70°C
Output Error (Notes 1, 9)
TA = -40°C to 0°C,
TA = +70°C to +85°C
Power-Supply Rejection Ratio
°C
0.13
PSRR
(Note 7)
Noise
MAX129_A
±0.75
MAX129_B
±1
MAX129_C
MAX129_A
±0.75
MAX129_B
±1
±1
MAX129_C
±2
MAX129_A
±0.75
MAX129_B
±1
°C
±4
MAX129_C
0.2
°C/V
0.18
°CRMS
EXTERNAL TEMPERATURE MEASUREMENT CHARACTERISTICS
Output Error
2N3904 (Note 10)
±2
±4
°C
Remote Diode Excitation (1X)
10
µA
Remote Diode Excitation (10X)
100
µA
4
_______________________________________________________________________________________
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
(VDD = +4.75V to 5.25V (MAX1298), VDD = +2.7V to +3.6V (MAX1299), external reference, VREF = +2.5V (MAX1298), VREF = +1.2V
(MAX1299), fSCLK = 2.5MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Figures 4, 6)
PARAMETER
SCLK Frequency
SYMBOL
fSCLK
CONDITIONS
MIN
TYP
MAX
2.5
UNITS
MHz
SCLK Pulse Width Low
tCL
200
ns
SCLK Pulse Width High
tCH
200
ns
CS Low to SCLK High
tCSS
100
ns
SCLK High to CS Setup
tCSH
100
ns
CS Pulse Width
tCS
100
ns
SCLK High to CS Low Setup
tCS0
50
ns
SCLK High to CS High Setup
tCS1
100
ns
DIN Setup to SCLK High Time
tDS
100
ns
DIN Hold Time
tDH
0
SCLK Fall to Output Data Valid
tDO
RL = 100kΩ, CL = 50pF
150
ns
CS Fall to Output Enable
tDV
RL = 100kΩ, CL = 50pF
150
ns
CS Rise to Output Disable
tTR
RL = 100kΩ, CL = 50pF
50
SSTRB Rise to SCLK Rise
tSCLK
SCLK Fall to SSTRB Fall
tSSTRB
ns
0
ns
ns
200
ns
Note 1: Tested at VDD = +5.0V (MAX1298) and VDD = +3.0V (MAX1299).
Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range has
been calibrated.
Note 3: Conversion time is defined as the number of clock cycles (64 for voltage measurements, 125 for temperature measurements) multiplied by the internal clock period.
Note 4: Individual analog input voltages cannot extend beyond the power-supply rails.
Note 5: Input resistance is typically 250MΩ; 5µA limit reflects limitations in production testing.
Note 6: Specifications for full-on status assume continuous conversions. Power modes are software selected (Table 4).
Note 7: Measured at VFS(+4.75V) - VFS(+5.25V) for the MAX1298 and at VFS(+2.7V) - VFS(+3.6V) for the MAX1299.
Note 8: External load should not change during conversions for specified accuracy.
Note 9: Excludes noise and self-heating effects. Output error for MAX129_C guaranteed by design.
Note 10: External temperature sensing over -40°C to +85°C range, device at +25°C. Guaranteed by design.
_______________________________________________________________________________________
5
MAX1298/MAX1299
TIMING CHARACTERISTICS
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAX1299
INTEGRAL NONLINEARITY
vs. OUTPUT CODE
0.4
0.2
0
-0.2
-0.4
-0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-1.0
-2500
-1.0
-2500
-1250
0
1250
2500
1.0
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1250
0
1250
-1.0
-2500
2500
-1250
0
1250
2500
OUTPUT CODE
OUTPUT CODE
OUTPUT CODE
MAX1299
DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODE
MAX1298
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(VOLTAGE MEASUREMENT MODE)
MAX1299
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(VOLTAGE MEASUREMENT MODE)
450
0.2
0
-0.2
-0.4
350
450
400
SUPPLY CURRENT (µA)
0.4
INTERNAL REFERENCE
400
SUPPLY CURRENT (µA)
0.6
500
EXTERNAL REFERENCE
300
250
200
150
250
200
150
100
-0.8
50
50
0
1250
0
4.7
2500
EXTERNAL REFERENCE
300
100
0
INTERNAL REFERENCE
350
-0.6
-1250
MAX1298/9-06
500
MAX1298/9-05
0.8
-1.0
-2500
MAX1298/9-03
0.6
-0.8
MAX1298/9-04
4.8
4.9
5.0
5.1
5.2
2.7
2.9
3.1
3.3
3.5
OUTPUT CODE
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
MAX1298
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(TEMPERATURE MEASUREMENT MODE)
MAX1299
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(TEMPERATURE MEASUREMENT MODE)
MAX1298
SUPPLY CURRENT vs. TEMPERATURE
(VOLTAGE MEASUREMENT MODE)
350
EXTERNAL REFERENCE
300
250
200
150
INTERNAL REFERENCE
400
SUPPLY CURRENT (µA)
INTERNAL REFERENCE
450
EXTERNAL REFERENCE
350
500
300
250
200
150
450
350
250
200
150
100
50
50
50
0
0
4.9
5.0
5.1
SUPPLY VOLTAGE (V)
5.2
EXTERNAL REFERENCE
300
100
4.8
INTERNAL REFERENCE
400
100
4.7
MAX1298/9-09
450
400
500
MAX1298/9-07
500
SUPPLY CURRENT (µA)
DIFFERENTIAL NONLINEARITY (LSB)
0.8
-0.8
1.0
6
MAX1298/9-02
0.6
1.0
MAX1298/9-08
INTEGRAL NONLINEARITY (LSB)
0.8
INTEGRAL NONLINEARITY (LSB)
MAX1298/9-01
1.0
MAX1298
DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODE
DIFFERENTIAL NONLINEARITY (LSB)
MAX1298
INTEGRAL NONLINEARITY
vs. OUTPUT CODE
SUPPLY CURRENT (µA)
MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
0
2.7
2.9
3.1
3.3
SUPPLY VOLTAGE (V)
3.5
-40
-20
0
20
40
TEMPERATURE (°C)
_______________________________________________________________________________________
60
80
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
350
EXTERNAL REFERENCE
300
250
200
150
EXTERNAL REFERENCE
300
250
200
150
300
250
200
150
50
50
50
0
0
0
20
40
60
80
-40
-20
0
20
40
60
-40
80
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX1298
POWER-DOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1299
POWER-DOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1298
POWER-DOWN SUPPLY CURRENT
vs. TEMPERATURE
350
300
250
STANDBY+
200
150
STANDBY
500
350
300
250
200
STANDBY+
150
STANDBY
450
400
350
300
250
150
100
100
50
50
50
0
0
4.9
5.0
5.1
5.2
STANDBY+
200
100
4.8
MAX1298/9-15
400
SUPPLY CURRENT (µA)
400
450
SUPPLY CURRENT (µA)
450
MAX1298/9-14
500
MAX1298/9-13
500
STANDBY
0
2.7
2.9
3.1
3.3
3.5
-40
-20
0
20
40
60
80
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
MAX1299
POWER-DOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1298
INTERNAL REFERENCE VOLTAGE
vs. SUPPLY VOLTAGE
MAX1299
INTERNAL REFERENCE VOLTAGE
vs. SUPPLY VOLTAGE
REFERENCE VOLTAGE (V)
400
350
300
250
200
STANDBY+
150
STANDBY
100
1.22
REFERENCE VOLTAGE (V)
450
2.51
2.50
2.49
MAX1298/9-18
2.52
MAX1298/9-16
500
MAX1298/9-17
4.7
EXTERNAL REFERENCE
350
100
-20
INTERNAL REFERENCE
400
100
-40
SUPPLY CURRENT (µA)
350
450
100
0
SUPPLY CURRENT (µA)
INTERNAL REFERENCE
400
SUPPLY CURRENT (µA)
INTERNAL REFERENCE
450
SUPPLY CURRENT (µA)
400
500
MAX1298/9-11
450
SUPPLY CURRENT (µA)
500
MAX1298/9-10
500
MAX1299
SUPPLY CURRENT vs. TEMPERATURE
(TEMPERATURE MEASUREMENT MODE)
MAX1298
SUPPLY CURRENT vs. TEMPERATURE
(TEMPERATURE MEASUREMENT MODE)
MAX1298/9-12
MAX1299
SUPPLY CURRENT vs. TEMPERATURE
(VOLTAGE MEASUREMENT MODE)
1.21
1.20
1.19
50
0
2.48
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
1.18
4.7
4.8
4.9
5.0
5.1
SUPPLY VOLTAGE (V)
5.2
2.7
2.9
3.1
3.3
3.5
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
7
MAX1298/MAX1299
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX1298
INTERNAL REFERENCE VOLTAGE
vs. TEMPERATURE
MAX1299
INTERNAL REFERENCE VOLTAGE
vs. TEMPERATURE
2.51
2.50
2.49
2.48
-20
0
20
40
60
1.20
1.19
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX1298
OFFSET vs. SUPPLY VOLTAGE
MAX1299
OFFSET vs. SUPPLY VOLTAGE
MAX1298/9-22
1.0
MAX1298/9-21
1.0
0.5
OFFSET (LSB)
0.5
0
0
-0.5
-0.5
-1.0
-1.0
4.7
4.8
4.9
5.0
5.1
2.7
5.2
2.9
3.1
3.3
3.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
MAX1298
OFFSET vs. TEMPERATURE
MAX1299
OFFSET vs. TEMPERATURE
1.0
MAX1298/9-23
1.0
0.5
OFFSET (LSB)
0.5
MAX1298/9-24
OFFSET (LSB)
1.21
1.18
-40
0
-0.5
0
-0.5
-1.0
-1.0
-40
-20
0
20
40
TEMPERATURE (°C)
8
MAX1298/9-20
MAX1298/9-19
1.22
REFERENCE VOLTAGE (V)
REFERENCE VOLTAGE (V)
2.52
OFFSET (LSB)
MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
60
80
-40
-20
0
20
40
60
TEMPERATURE (°C)
_______________________________________________________________________________________
80
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
(TA = +25°C, unless otherwise noted.)
MAX1298
GAIN ERROR vs. TEMPERATURE
MAX1299
GAIN ERROR vs. TEMPERATURE
0.5
GAIN ERROR (LSB)
0
-0.5
-0.5
-1.0
-1.0
-40
-20
0
20
40
60
80
-20
0
20
40
60
80
TEMPERATURE (°C)
MAX1298
TEMPERATURE ERROR
vs. INTERNAL DIODE TEMPERATURE
MAX1299
TEMPERATURE ERROR
vs. INTERNAL DIODE TEMPERATURE
0.5
0
-0.5
-1.0
MAX1298/9-30
MAX1298/9-29
1.0
TEMPERATURE ERROR (°C)
TEMPERATURE ERROR (°C)
-40
TEMPERATURE (°C)
1.0
0.5
0
-0.5
-1.0
-60 -40
-20
0
20
40
60
80
100
-60 -40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX1298
TEMPERATURE ERROR
vs. REMOTE DIODE TEMPERATURE
MAX1299
TEMPERATURE ERROR
vs. REMOTE DIODE TEMPERATURE
2.0
MAX1298/9-31
2.0
1.5
TEMPERATURE ERROR (°C)
1.5
TEMPERATURE ERROR (°C)
0
1.0
0.5
0
-0.5
-1.0
100
MAX1298/9-32
GAIN ERROR (LSB)
0.5
MAX1298/9-28
1.0
MAX1298/9-27
1.0
1.0
0.5
0
-0.5
-1.0
-1.5
-1.5
-2.0
-2.0
-60
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
100
-60
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
9
MAX1298/MAX1299
Typical Operating Characteristics (continued)
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
MAX1298/MAX1299
Pin Description
10
PIN
NAME
FUNCTION
1
AIN1
Analog Input 1. Negative differential input relative to AIN0 or positive differential input relative to AIN5
(Table 5). Connect to the cathode of external diode 1 for remote temperature sensing.
2
SHO
Shield Output. Used to suppress leakage currents at the anodes of remote temperature sensors (see Remote
Diode Shielding). May also be connected to the shield of twisted-pair input cables used for remote
temperature measurements. Leave unconnected for other applications.
3
AIN2
Analog Input 2. Positive differential input relative to AIN3 or positive differential input relative to AIN5
(Table 5). Connect to the anode of external diode 2 for remote temperature sensing.
4
AIN3
Analog Input 3. Negative differential input relative to AIN2 or positive differential input relative to AIN5
(Table 5). Connect to the cathode of external diode 2 for remote temperature sensing.
5
AIN4
Analog input 4. Positive differential input relative to AIN5 (Table 5).
6
GND
Ground. Connect to pin 13.
7
SSTRB
8
CS
9
DOUT
10
DIN
Serial Data Input. DIN latches data on the rising edge of SCLK.
11
SCLK
Serial Clock Input. Clocks data in and out of the serial interface.
12
VDD
Positive Supply Voltage. Bypass with a 0.1µF capacitor to GND (pin 13).
13
GND
Ground (star ground)
14
REF
Reference-Buffer Output/ADC Reference Input. Reference voltage for A/D conversion. Bypass to GND (pin 13)
with a 0.1µF capacitor. Select reference mode by writing to configuration byte (Table 2).
15
AIN5
Analog Input 5. Negative differential input relative to AIN0–AIN4 (Table 5).
16
AIN0
Analog Input 0. Positive differential input relative to AIN1 or positive differential input relative to AIN5
(Table 5). Connect to the anode of external diode 1 for remote temperature sensing.
Serial Strobe Output. SSTRB goes low at the beginning of an A/D conversion, and it goes high when the
conversion is finished.
Active-Low Chip Select. Data will not be clocked into DIN unless CS is low. When CS is high, DOUT is at high
impedance.
Serial Data Output. DOUT transitions on the falling edge of SCLK.
______________________________________________________________________________________
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
MAX1298/MAX1299
CS
SCLK
INPUT
REGISTER
DIN
OUTPUT
REGISTER
MAX1298
MAX1299
DIODE
BIAS
CONTROL
DOUT
CONTROL
LOGIC
CLOCK
AIN0
AIN1
IN+
T/H
AIN2
AIN3
INPUT
MUX
12-BIT
ADC
AIN4
AIN5
IN-
T/H
VDD
GND
SHIELD
OUTPUT
VDD/4
SHO
REF
REF
Figure 1. Functional Diagram
Detailed Description
The MAX1298/MAX1299 are low-power, serial-output,
multichannel ADCs with temperature-sensing capability
for thermostatic, process-control, and monitoring applications. An algorithmic switched-capacitor converter
with T/H circuitry for both positive and negative inputs
supports fully differential 12-bit conversions from an
internal temperature sensor, two external temperature
sensors, or voltage sources in a variety of channel con-
figurations. Microprocessor (µP) control is made easy
through a flexible 3-wire serial interface.
Figure 1 shows a simplified functional diagram of the
internal architecture for the MAX1298/MAX1299. In temperature-sensing mode, the multiplexer (mux) steers
bias currents through internal or external diodes while
the ADC computes their temperature in relation to
changes in forward voltage. Channels not used for temperature measurement can be configured to measure
other system voltages.
______________________________________________________________________________________________________
11
MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
TIMING/CONTROL
LOGIC
RIN
40k
IN+
T/H
CHOLDP
4pF
FULLY
DIFFERENTIAL
A/D
OUTPUT
RIN
40k
INT/H
CHOLDN
4pF
TRACK AND HOLD
RR
30k
REF
CREF
4pF
GAIN
OF 2
Figure 2. Converter Input Structure
Converter Operation
Figure 2 shows a simplified model of the converter
input structure. Once initiated, a voltage conversion
requires 64 fCLK periods, where fCLK is the internal
master clock. Each conversion is preceded by 13 fCLK
periods of warm-up time, performed in twelve 4 fCLK
period cycles, and followed by 3 fCLK periods to load
the output register. SSTRB falls at the beginning of a
conversion and rises at the end of a conversion.
Inputs IN+ and IN- charge capacitors CHOLDP and
CHOLDN, respectively, during the acquisition interval
that occurs during the first fCLK period of the first conversion cycle. In the second f CLK period, the T/H
switches open so that charge is retained on CHOLDP
and CHOLDN as a sample of the differential voltage
between IN+ and IN-. This charge is transferred to the
ADC during the third and fourth fCLK periods.
The reference sampling process begins in the second
conversion cycle and continues until the conversion is
complete. Sampling occurs during the second and
fourth fCLK periods to yield an effective doubling of the
reference voltage. The reference sampling requirement
12
is signal dependent and may or may not occur in every
subsequent conversion cycle.
Temperature conversion is essentially nothing more than
subtracting the results of two sequential voltage conversions. The only difference is that output registers are not
loaded at the end of the first conversion. Thus, temperature conversions require 2 x 64 - 3 = 125 fCLK periods.
Figures 3a and 3b show timing diagrams for voltage
and temperature conversions, respectively.
Track/Hold
The T/H stage for the MAX1298/MAX1299 is a simple
switched-capacitor sampling operation. The time
required for the T/H stage to acquire an input signal is
a function of how fast its input capacitance is charged.
If the signal source impedance is high, the acquisition
time lengthens and more time must be allowed
between conversions. The acquisition time (tACQ) is the
maximum time the device takes to acquire the signal.
Calculate this with the following equation:
tACQ = 7 (Rs + RIN) CIN
where Rs is the source impedance of the input signal,
RIN is the T/H input impedance (40kΩ), and CIN is the
______________________________________________________________________________________
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
MAX1298/MAX1299
SSTRB
FCLK
13 fCLKs
WARMUP
3 fCLKs
WRITE TO OUTPUT
REGISTER
REF
ACQUISITION 1
REF
ACQUISITION 2
44 fCLKs
INPUT
ACQUISITION
fCLKs
CONVERSION CYCLE 1
CONVERSION CYCLES 2–12
REFERENCE SAMPLING
Figure 3a. Voltage Conversion Timing Diagram
SSTRB
FCLK
13 fCLKs
WARMUP
INPUT
ACQUISITION
4 fCLKs
CONVERSION CYCLE 1
44 fCLKs
CONVERTION
CYCLES 2–12
REFERENCE
SAMPLING
FIRST CONVERSION
13 fCLKs
WARMUP
3 fCLKs
SUBTRACTION
AND WRITE TO
OUTPUT REGISTER
INPUT
ACQUISITION
48 fCLKs
CONVERTION CYCLES 1–12
SECOND CONVERSION
Figure 3b. Temperature Conversion Timing Diagram
input sampling capacitance of the ADC (4pF). Source
impedances below 100kΩ have no significant effect on
MAX1298/MAX1299 AC performance.
Analog Input Protection
Internal protection diodes clamp the analog inputs to
VDD and GND, so channels can swing within GND 0.3V and VDD + 0.3V without damage. However, for
accurate conversions, the inputs should not extend
beyond the supply rails.
If an off-channel analog input extends beyond the
supply rails, limit the input current to 2mA.
Serial Digital Interface
The MAX1298/MAX1299 feature a serial interface that is
fully compatible with SPI, QSPI, and MICROWIRE
devices. For SPI/QSPI, ensure that the CPU serial interface runs in master mode so it generates the serial
clock signal. Select a 2.5MHz clock frequency or less,
and set zero values for clock polarity (CPOL) and
phase (CPHA) in the µP control registers. Figure 4
shows detailed serial interface timing information. See
Tables 2–5 for programming information.
______________________________________________________________________________________
13
MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
CS
t CS
t CSS
t CSO
t CH
t CS1
t CSH
SCLK
t DH
t CL
t DS
X
DIN
VALID
X
t DV
VALID
t DO
VALID
X
t TR
DOUT
Figure 4. Detailed Serial Interface Timing
Output Data Format
Output data from the MAX1298/MAX1299 are clocked
onto DOUT on the falling edge of SCLK in the form of two
8-bit words, MSB first (Table 1). For temperature conversions, the output is 12-bit binary (D10–S0) padded with 2
leading extraneous bits and two trailing zeros. For voltage conversions, the output is 12-bit two’s-complement
binary (D11–D0) with 1 sub-bit and two trailing zeros.
Figure 5 shows the bipolar transfer function.
OUTPUT CODE
011111111111
011111111110
000000000010
000000000001
000000000000
111111111111
111111111110
111111111101
+FS = + 2VREF
-FS = - 2VREF
1LSB = 2VREF
2048
Performing a Conversion
100000000010
100000000001
- FS + 1LSB
0
+ FS - 1LSB
IN+ - IN - (LSB)
Figure 5. Bipolar Transfer Function
Input Data Format
Input data (configuration and conversion bytes) are
clocked into the MAX1298/MAX1299 at DIN on the rising edge of SCLK when CS is low. The start bit (MSB)
of an input data byte is the first logic 1 bit that arrives:
After CS falls,
OR
after receipt of a complete configuration byte with no
conversion in progress,
OR
after 16 bits have been clocked onto DOUT following a
conversion.
14
On power-up, the MAX1298/MAX1299 defaults to shutdown mode. Start a conversion by transferring a configuration byte and a conversion byte into DIN with the
control formats shown in Tables 2 and 3, respectively.
(See Power Modes for related discussion.)
SSTRB goes low on the falling edge of the last bit of the
conversion byte, and it returns high when the conversion
is complete. For best noise performance, SCLK should
remain low while SSTRB is low. Typical conversion times
are 2.2ms for temperature measurements and 1.1ms for
voltage measurements. The MSB of the 2 output bytes is
present at DOUT starting at the rising edge of SSTRB.
Successive SCLK falling edges shift the two 8-bit data
bytes out from an internal register. Additional (>16)
SCLK edges will result in zeros on DOUT.
SSTRB does not go into a high-impedance state when
CS goes high. Pulling CS high prevents data from
being clocked in or out, but it does not adversely affect
a conversion in progress. Figure 6 shows SSTRB timing
details.
Subsequent conversions with the same reference mode
do not require a configuration byte.
______________________________________________________________________________________
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
D11
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
S0
0
0
Table 2. Configuration-Byte Format
BIT 7
(MSB)
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
(LSB)
Start
0
0
0
0
PM1
PM0
REF
BIT
NAME
7 (MSB)
Start
DESCRIPTION
First logic 1 after CS goes low. (See Input Data Format.)
6, 5, 4, 3
Must be 0000 to load a configuration byte.
2, 1
PM1, PM0
0
REF
These 2 bits select the desired power mode (Table 4).
A logic high enables the internal reference. A logic low disables the internal reference and
selects the external reference mode.
Table 3. Conversion-Byte Format
BIT 7
(MSB)
Start
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
0
1
0
SEL3
SEL2
SEL1
BIT
NAME
7 (MSB)
Start
DESCRIPTION
First logic 1 after CS goes low. (See Input Data Format.)
6, 5, 4
3, 2, 1, 0
Must be 010 to load a conversion byte.
SEL3, SEL2,
SEL1, SEL0
These 4 bits select the input configuration (Table 5).
CSB
t CSH
SSTRB
BIT 0
(LSB)
SEL0
t CSS
t SCK
t CONV
t SSTRB
SCLK
t DO
PDO CLOCKED IN
DOUT
SSTRB TIMING
Figure 6. Detailed SSTRB Timing
Reference Selection
Select between internal and external voltage modes
through bit REF of the configuration byte. Set REF = 1
for internal reference mode and REF = 0 for external
reference mode.
Internal Reference
The MAX1298 has a 2.50V internal reference, while the
MAX1299 has a 1.20V internal reference. Both are factory trimmed for accuracy. When internal reference is
selected, REF can be used to drive an external load
with 100µA capability. Bypass REF to GND with a 0.1µF
(min) capacitance. Wake-up time is C x 2.5 x 104s for
the MAX1298 and C x 1.2 x 104s for the MAX1299.
External Reference
The MAX1298 can directly accept reference voltages at
REF from 0.8V to 2.5V, while the MAX1299 can directly
accept reference voltages from 0.8V to 1.2V. Bypass
REF to GND with a 0.1µF capacitor. Temperature measurements always use internal reference.
Power Modes
The MAX1298 (MAX1299) typically requires supply currents of 380µA (350µA) or 310µA (280µA) when performing voltage conversions at 100% duty cycle with
internal or external references, respectively. The differ-
______________________________________________________________________________________
15
MAX1298/MAX1299
Table 1. Output Data Format
MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
ence reflects the power requirement of an internal reference buffer amplifier that can accommodate external
loads. Temperature conversions at 100% duty cycle
increase supply currents to 440µA (400µA) through
additional amplification, buffer, and bias circuitry that is
otherwise inactive.
Place the MAX1298/MAX1299 in a low-current powerdown state between conversions to conserve power.
Select standby, standby-plus, or shutdown through bits
PM1 and PM0 of the initialization byte (Table 4).
The MAX1298/MAX1299 assume the shutdown power
mode when VDD is first applied.
Standby Mode
Standby mode turns off the MAX1298/MAX1299 ADC,
internal clock, and reference buffer amplifier. Special
circuitry for temperature conversions is also deactivated. Wake-up time is limited by the reference buffer
amplifier and the associated bypass capacitor (see
Internal Reference). When an external reference is
used, wake-up time is 0.1ms.
Standby-Plus Mode
Standby-plus mode is similar to the standby mode, but
the internal reference output buffer remains active to
shorten the wake-up time to 0.1ms for internal reference mode. When using an external reference, standby-plus mode is equivalent to standby mode.
Table 4. Power-Mode Selection
PM1
0
PM0
0
0
1
MODE
Shutdown
Standby-plus
1
0
Standby
1
1
Normal operation
achieve a digital output that is proportional to absolute
temperature in degrees Kelvin.
The reference voltage used in conjunction with temperature measurements is derived from the internal reference
source to ensure that 1LSB corresponds to 1/8 of a
degree. To convert to degrees Celsius, subtract 273.15
from the temperature inferred from the ADC output.
Temperature measurements require a conversion time
of 2.2ms.
Shield Output Buffer
The MAX1298/MAX1299 provide a shield output buffer
voltage at SHO that is approximately 0.6V (one diode
drop) above V DD /2. When performing temperature
measurements with an external diode, use this voltage
to suppress error-producing leakage currents (see
Remote Diode Shielding). Figure 7 shows the SHO output circuit.
Shutdown Mode
Shutdown mode turns off all functions other than startup circuitry, thereby reducing typical supply current to
2µA. Data registers are cleared. Use this power mode
when interconversion times are no less than 5ms.
5µA
SHO
Monitoring VDD
This mode of operation samples and converts the supply voltage, VDD/4, which is internally generated. The
reference voltage must be larger than VDD/8 for the
operation to work properly. From the result of a conversion (CODE), CODE = 256 VDD / VREF.
VDD
2
Figure 7. SHO Output Circuit
Temperature Measurements
The MAX1298/MAX1299 perform temperature measurements with internal or external diode-connected transistors through a three-step process. First, the diode bias
current changes from 31.6µA to 10µA to produce a
temperature-dependent bias voltage difference, which
is amplified by a factor of 20 and converted to digital
format. Second, the bias current changes from 31.6µA
to 100µA, and the bias voltage difference is similarly
amplified by a factor of 20 and converted to digital format. Third, the intermediate results are subtracted to
16
Applications Information
Remote Diode Selection
Temperature accuracy depends on having a goodquality, diode-connected small-signal transistor.
Accuracy has been experimentally verified for 2N3904
devices. CPUs and other ICs having on-board temperature-sensing diodes can also be monitored if the
diode connections are floating.
______________________________________________________________________________________
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
MAX1298/MAX1299
Table 5. Input Selection
SEL3
SEL2
SEL1
SEL0
POSITIVE INPUT (IN+)
NEGATIVE INPUT (IN-)
0
0
0
0
AIN0
AIN5
0
0
0
1
AIN1
AIN5
0
0
1
0
AIN2
AIN5
0
0
1
1
AIN3
AIN5
0
1
0
0
AIN4
AIN5
0
1
0
1
—
—
0
1
1
0
AIN5
AIN5
0
1
1
1
Internal diode anode*
Internal diode cathode
1
0
0
0
AIN0
AIN1
1
0
0
1
AIN2
AIN3
1
0
1
0
—
—
1
VDD/4
GND
1
0
1
1
1
0
0
External diode 1 anode* (AIN0)
External diode 1 cathode
(AIN1)
1
1
0
1
External diode 2 anode* (AIN2)
External diode 2 cathode
(AIN3)
1
1
1
0
—
—
1
1
1
1
—
—
*Temperature-measurement mode
Table 6. Remote-Sensor Transistor
Manufacturer
MANUFACTURER
MODEL NUMBER
Central Semiconductor
(USA)
CMPT3904
Fairchild Semiconductor
(USA)
MMBT3904
Motorola (USA)
MMBT3904
Rohm Semiconductor
(Japan)
SST3904
Siemens (Germany)
SMB3904
Zetex (England)
FMMT3904CT-ND
The transistor must be a small-signal type with a base
resistance less than 100Ω. Tight specifications for forward current gain (+50 to +150, for example) indicate
that the manufacturer has good process controls and
that the devices have consistent Vbe characteristics.
(See Table 6 for recommended devices.)
For heatsink mounting, the 500-32BT02-000 thermal
sensor from Fenwal Electronics is a good choice. This
device consists of a diode-connected transistor, an aluminum plate with screw hole, and twisted-pair cable
(Fenwal Inc., Milford MA, 508-478-6000).
Twisted-Pair and Shielded Cables
For remote-sensor distances greater than 8 inches, or
in particularly noisy environments, use a twisted pair. A
practical length is 6 to 12 feet. For longer distances, the
best solution is a shielded twisted pair such as that
used for audio microphones. For example, the Belden
8451 works well for distances up to 100 feet in a noisy
environment. Connect the shield to SHO.
Cable resistances affect remote-sensor accuracy; 1Ω
series resistance introduces +0.004°C error.
Remote Diode Shielding
Temperature measurements will reflect significant error
if a portion of the bias current supplied to the diode
anode is allowed to flow through parallel paths to
ground. If the diode-connected transistor is mounted
on a PC board, suppress error-producing “leakage”
current by surrounding the collector/base leads with a
metal trace that is connected to the SHO shield output
(Figure 8).
______________________________________________________________________________________
17
MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
SHIELD
ANODE
between the endpoints of the transfer function, once
offset and gain errors have been nullified. The static linearity parameters for the MAX1298/MAX1299 are measured using the best-straight-line-fit method.
Differential Nonlinearity (DNL)
Differential nonlinearity is the difference between an
actual step width and the ideal value of 1LSB. A DNL
error specification of less than 1LSB guarantees no
missing codes and a monotonic transfer function.
Offset Error
The offset error is the difference between the ideal and
the actual offset points. For an ADC, the offset point is
the midstep value when the digital output is zero.
Gain Error
CATHODE
Figure 8. Remote Diode Shielding for PC Boards
Layout, Grounding, and Bypassing
For best performance, use PC boards. Do not use wirewrap boards. Board layout should ensure that digital
and analog signal lines are separated from each other.
Do not run analog and digital (especially clock) signals
parallel to one another or run digital lines underneath
the ADC package.
High-frequency noise in the VDD power supply may
affect ADC performance. Bypass the supply with a
0.1µF capacitor close to pin VDD. Minimize capacitor
lead lengths for best supply-noise rejection. If the
power supply is very noisy, connect a 10Ω resistor in
series with the supply to provide lowpass filtering.
The gain or full-scale error is the difference between
the ideal and actual gain points on the transfer function,
after the offset error has been canceled out. For an
ADC, the gain point is the midstep value when the digital output is full scale.
Aperture Delay
Aperture delay (tAD) is the time defined between the
rising edge of the sampling clock and the instant when
an actual sample is taken.
Chip Information
TRANSISTOR COUNT: 13,669
PROCESS: BiCMOS
Definitions
Relative Accuracy
Relative accuracy is the deviation of the values on an
actual transfer function from a straight line. This straight
line can be either a best-straight-line fit or a line drawn
18
______________________________________________________________________________________
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
0.1µF
+5V
VDD
AIN0
AIN1
2N3904
2N3904
CS
MAX1298
(SHIELD)
AIN2
SCLK
AIN3
DIN
SHO
DOUT
AIN4
SSTRB
AIN5
GND
GND
______________________________________________________________________________________
19
MAX1298/MAX1299
Typical Operating Circuit
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
SSOP.EPS
MAX1298/MAX1299
Package Information
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.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
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Printed USA
is a registered trademark of Maxim Integrated Products.