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MAX6691MUB+

P1-P3P4-P6P7-P7
General Description
The MAX6691 four-channel thermistor temperature-to-
pulse-width converter measures the temperatures of up
to four thermistors and converts them to a series of out-
put pulses whose widths are related to the thermistors’
temperatures. Each of the four thermistors and an
external fixed resistor (R
EXT
) form a voltage-divider that
is driven by the MAX6691’s internal voltage reference
(V
REF
). V
REF
and the voltage across R
EXT
are mea-
sured and converted to a pulse.
The MAX6691 has a single open-drain I/O pin that can
be readily connected to a variety of microcontrollers.
The microcontroller initiates a conversion by pulling the
I/O pin low and releasing it. When conversion is done,
the MAX6691 signals the end of conversion by pulling
the I/O pin low once again. The pulse corresponding to
the first thermistor is sent immediately after the release
of the I/O pin.
The on-chip power-management circuitry reduces the
average thermistor current to minimize errors due to
thermistor self-heating. Between conversions, the
MAX6691 falls into a 10µA (max) sleep mode, where
the voltage reference is disabled and the supply cur-
rent is at its minimum.
The MAX6691 is available in a 10-pin µMAX package
and is specified from -55°C to +125°C temperature
range.
Applications
HVAC
Home Appliances
Medical Devices
Features
♦ Simple Single-Wire Interface
♦ Measures Up to Four Thermistor Temperatures
♦ Low-Average Thermistor Current Minimizes Self-
Heating Errors
♦ Internal Voltage Reference Isolates Thermistor
from Power-Supply Noise
♦ Accommodates Any Thermistor Temperature
Range
MAX6691
Four-Channel Thermistor Temperature-to-Pulse-
Width Converter
________________________________________________________________ Maxim Integrated Products 1
1
2
3
4
5
10
9
8
7
6
V
CC
I/O
N.C.
GNDT4
T3
T2
T1
MAX6691
µMAX
TOP VIEW
R+R-
Pin Configuration
1
2
3
4
5
10
9
8
7
6
V
CC
I/O
N.C.
GND
T4
T3
T2
T1
MAX6691
TOP VIEW
R+
R-
T4
T3
T2
T1
MICRO-
CONTROLLER
10kΩ
V
CC
R
EXT
Typical Application Circuit
19-2304; Rev 1; 2/07
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
PKG
CODE
MAX6691MUB
-55°C to +125°C
10 µMAX
U10-2
MAX6691
Four-Channel Thermistor Temperature-to-Pulse-
Width Converter
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
Note 1: Specification limits over temperature are guaranteed by design, not production tested.
V
CC
to GND...........................................................-0.3V to +6.0V
All Other Pins to GND.................................-0.3V to (V
CC
+ 0.3V)
I/O, R+, R-, T1–T4 Current................................................±20mA
ESD Protection (Human Body Model) .............................±2000V
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ........444.4mW
Operating Temperature Range .........................-55°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
ELECTRICAL CHARACTERISTICS
(V
CC
= 3.0V to 5.5V, T
A
= -55°C to +125°C, unless otherwise noted. Typical values are specified at V
CC
= 3.3V and T
A
= +25°C.) (Note1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
T
A
= +25°C, V
CC
= 3.3V 0.5
T
HIGH
/T
LOW
Accuracy V
REXT
T
A
= T
MIN
to T
MAX
1.0
Supply Voltage Range V
CC
3.0 5.5 V
Supply Current I
CC
During conversion, no load
300 600
µA
Sleep-Mode Supply Current
I
STANDBY
3.5 10 µA
Input Leakage Current
I
LEAKAGE
1.0 µA
Reference Voltage Output V
REF
I
REF
= 1mA, T
A
= +25°C
1.19 1.24 1.32
V
Reference Load Regulation 0 < I
REF
< 2mA 0.1 0.2 %
Reference Supply Rejection 0.2 %
Logic Input Low Voltage V
IL
0.3
✕
V
CC
V
Logic Input High Voltage V
IH
0.7
✕
V
CC
V
TIMING CHARACTERISTICS
(V
CC
= 3.0V to 5.5V, T
A
= -55°C to +125°C, unless otherwise noted. Typical values are specified at V
CC
= 3.3V and T
A
= +25°C.)
(Figure 1) (Note1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
Glitch Immunity on I/O Input
500
ns
Conversion Time t
CONV
86
102 156
ms
Nominal Pulse Width t
LOW
4.0 4.9 7.5 ms
Start Pulse Width t
START
5µs
Data Ready Pulse Width t
READY
103 122 188
µs
Error Pulse Width t
ERROR
103 122 188
µs
Rise Time t
RISE
C
L
= 15pF, R
L
= 10kΩ
600
ns
Fall Time t
FALL
C
L
= 15pF, R
L
= 10kΩ
600
ns
MAX6691
Four-Channel Thermistor Temperature-to-Pulse-
Width Converter
_______________________________________________________________________________________ 3
SLEEP-MODE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6691 toc01
SUPPLY VOLTAGE (V)
SLEEP-MODE SUPPLY CURRENT (µA)
5.04.54.03.5
3.0
3.5
4.0
4.5
2.5
3.0 5.5
T
HIGH
/T
LOW
ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6691 toc02
POWER-SUPPLY NOISE FREQUENCY (MHz)
T
HIGH
/T
LOW
FULL-SCALE ERROR (%)
2015105
-0.5
0
0.5
1.0
-1.0
025
V
CC
= 5.0V
V
CC
= 3.3V
V
IN
= SQUARE WAVE
APPLIED TO V
CC
WITH
NO VCC BYPASS
CAPACITOR
V
IN
= 250mV
P-P
T
HIGH
/T
LOW
ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6691 toc03
POWER-SUPPLY NOISE FREQUENCY (MHz)
T
HIGH
/T
LOW
FULL-SCALE ERROR (%)
2015105
-0.5
0
0.5
1.0
-1.0
025
T
A
= +25°C
T
A
= -55°C
T
A
= +85°C
T
A
= +125°C
V
IN
= SQUARE WAVE
APPLIED TO V
CC
WITH
NO VCC BYPASS
CAPACITOR
V
IN
= 250mV
P-P
__________________________________________Typical Operating Characteristics
(V
CC
= 5V, R
EXT
= 7.5kΩ, R
TH
= 12.5kΩ, T
A
= +25°C, unless otherwise noted.)
PIN NAME FUNCTION
1 T1 Thermistor 1. Connect to external thermistor 1.
2 T2 Thermistor 2. Connect to external thermistor 2.
3 T3 Thermistor 3. Connect to external thermistor 3.
4 T4 Thermistor 4. Connect to external thermistor 4.
5 R- External Resistor Low Side. Connect R
EXT
between R- and R+.
6 R+ Reference Voltage Output. Connect R
EXT
between R- and R+.
7 GND Ground. Ground connection for MAX6691 and ground return for external thermistor(s).
8 N.C. No Connection. Do not make a connection to this pin.
9 I/O I/O Connection to Microcontroller. Connect a 10kΩ pullup resistor from I/O pin to V
CC
.
10 V
CC
Supply Voltage. Bypass V
CC
to GND with a capacitor of at least 0.1µF.
Pin Description
P1-P3P4-P6P7-P7

MAX6691MUB+

Mfr. #:
Buy MAX6691MUB+
Manufacturer:
Maxim Integrated
Description:
Sensor Interface 4Ch Thermistor Temp to-Pulse-Width
Lifecycle:
New from this manufacturer.
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