19-2032; Rev 4; 8/08
Remote ±1°C Accurate Digital Temperature
Sensors with SPI-Compatible Serial Interface
General Description
The MAX6627/MAX6628 precise digital temperature
sensors report the temperature of a remote sensor. The
remote sensor is a diode-connected transistor, typically
a low-cost, easily mounted 2N3904 NPN type that
replaces conventional thermistors or thermocouples.
The MAX6627/MAX6628 can also measure the die tem-
perature of other ICs, such as microprocessors (µPs) or
microcontrollers (µCs) that contain an on-chip, diode-
connected transistor.
Remote accuracy is ±1°C when the temperature of the
remote diode is between 0°C and +125°C and the tem-
perature of the MAX6627/MAX6628 is +30°C. The tem-
perature is converted to a 12-bit + sign word with
0.0625°C resolution. The architecture of the device is
capable of interpreting data as high as +145°C from
the remote sensor. The MAX6627/MAX6628 tempera-
ture should never exceed +125°C.
These sensors are 3-wire serial interface SPI™ compat-
ible, allowing the MAX6627/MAX6628 to be readily con-
nected to a variety of µCs. The MAX6627/MAX6628 are
read-only devices, simplifying their use in systems
where only temperature data is required.
Two conversion rates are available, one that continu-
ously converts data every 0.5s (MAX6627), and one
that converts data every 8s (MAX6628). The slower ver-
sion provides minimal power consumption under all
operating conditions (30µA, typ). Either device can be
read at any time and provide the data from the last con-
version.
Both devices operate with supply voltages between
+3.0V and +5.5V, are specified between -55°C and
+125°C, and come in space-saving 8-pin SOT23 and
lead-free TDFN packages.
Features
o
Accuracy
±1°C (max) from 0°C ≤ T
RJ
≤ +125°C, T
A
= +30°C
±2.4°C (max) from -55°C ≤ T
RJ
≤ +100°C,
0°C ≤ T
A
≤ +70°C
o
12-Bit + Sign, 0.0625°C Resolution
o
Low Power Consumption
30µA (typ) (MAX6628)
200µA (typ) (MAX6627)
o
Operating Temperature Range (-55°C to +125°C)
o
Measurement Temperature Range, Remote
Junction (-55°C to +145°C)
o
0.5s (MAX6627) or 8s (MAX6628) Conversion Rate
o
SPI-Compatible Interface
o
+3.0V to +5.5V Supply Range
o
8-Pin SOT23 and TDFN Packages
o
Lead-Free Version Available (TDFN Package)
MAX6627/MAX6628
Ordering Information
PART
MAX6627MKA#T
MAX6627MTA+T
MAX6628MKA#T
MAX6628MTA+T
PIN-PACKAGE
8 SOT23
8 TDFN-EP*
8 SOT23
8 TDFN-EP*
TOP MARK
AAEQ
+AUT
AAER
+AUU
Note:
All devices are specified over the -55°C to +125°C oper-
ating temperature range.
#Denotes
an RoHS-compliant package.
T = Tape and reel.
+Denotes
a lead-free/RoHS-compliant package.
*EP
= Exposed pad.
Typical Operating Circuit
+ 3V TO + 5.5V
0.1μF
Applications
Hard Disk Drive
Smart Battery Packs
Automotive
Industrial Control Systems
Notebooks, PCs
DXP
2200pF
DXN
V
CC
GND
MAX6627
MAX6628
SDO
CS
μC
SPI is a trademark of Motorola, Inc.
Pin Configurations appears at end of data sheet.
SCK
________________________________________________________________
Maxim Integrated Products
1
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.
Remote ±1°C Accurate Digital Temperature
Sensors with SPI-Compatible Serial Interface
MAX6627/MAX6628
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.)
V
CC
...........................................................................-0.3V to +6V
SDO, SCK, DXP,
CS
.....................................-0.3V to V
CC
+ 0.3V
DXN .......................................................................-0.3V to +0.8V
SDO Pin Current Range ......................................-1mA to +50mA
Current Into All Other Pins ..................................................10mA
ESD Protection (Human Body Model)................................2000V
Continuous Power Dissipation (T
A
= +70°C)
8-Pin SOT23 (derate 9.7mW/°C above +70°C)............777mW
8-Pin TDFN (derate 18.5mW/°C above +70°C) ......1481.5mW
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
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
(3.0V
≤
V
CC
≤
5.5V, -55°C
≤
T
A
≤
+125°C, unless otherwise noted. Typical values are at T
A
= +25°C, V
CC
= +3.3V, unless otherwise
noted.)
PARAMETER
TEMPERATURE
0°C
≤
T
RJ
≤
+125°C, T
A
= +30°C,
V
CC
= +3.3V
-55°C
≤
T
RJ
≤
+100°C, 0°C
≤
T
A
≤
+70°C,
V
CC
= +3.3V
-55°C
≤
T
RJ
≤
+145°C, 0°C
≤
T
A
≤
+70°C,
V
CC
= +3.3V
-55°C
≤
T
RJ
≤
+125°C, -55°C
≤
T
A
≤
+125°C,
V
CC
= +3.3V
Power-Supply Sensitivity
Resolution
Time Between Conversion Starts
Conversion Time
POWER SUPPLY
Supply Voltage Range
Supply Current, SCK Idle
V
CC
I
SDO
I
IDLE
I
CONV
Average Operating Current
Power-On Reset (POR)
Threshold
Current Sourcing for Diode
I
CC
Shutdown, V
CC
= +0.8V
ADC idle,
CS
= low
ADC converting
MAX6627
MAX6628
V
CC
, falling edge
High level
Low level
80
8
360
200
30
1.6
100
10
120
12
3.0
5.5
5
20
600
400
50
µA
V
µA
µA
V
t
SAMPLE
t
CONV
MAX6627
MAX6628
180
-1.0
-2.4
-4.5
-5.5
0.25
0.0625
0.5
8
250
320
±0.5
±1
+2.4
°C
+4.5
+5.5
0.7
°C/V
°C
s
ms
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Accuracy (Note 1)
2
_______________________________________________________________________________________
Remote ±1°C Accurate Digital Temperature
Sensors with SPI-Compatible Serial Interface
ELECTRICAL CHARACTERISTICS (continued)
(3.0V
≤
V
CC
≤
5.5V, -55°C
≤
T
A
≤
+125°C, unless otherwise noted. Typical values are at T
A
= +25°C, V
CC
= +3.3V, unless otherwise
noted.)
PARAMETER
LOGIC INPUTS (CS, SCK)
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
LOGIC OUTPUTS (SDO)
Output Low Voltage
Output High Voltage
V
OL
V
OH
I
SINK
= 1.6mA
I
SOURCE
= 1.6mA
V
CC
-
0.4
5
100
100
C
LOAD
= 10pF
C
LOAD
= 10pF
C
LOAD
= 10pF
C
LOAD
= 10pF
80
80
50
80
0.4
V
V
IL
V
IH
I
LEAK
V
CS
= V
SCK
= GND or V
CC
0.7 x
V
CC
1
0.3 x
V
CC
V
V
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX6627/MAX6628
TIMING CHARACTERISTICS
(Note 2, Figure 2)
Serial-Clock Frequency
SCK Pulse Width High
SCK Pulse Width Low
CS
Fall to SCK Rise
CS
Fall to Output Enable
CS
Rise to Output Disable
SCK Fall to Output Data Valid
f
SCL
t
CH
t
CL
t
CSS
t
DV
t
TR
t
DO
MHz
ns
ns
ns
ns
ns
ns
Note 1:
T
RJ
is the temperature of the remote junction.
Note 2:
Serial timing characteristics guaranteed by design.
_______________________________________________________________________________________
3
Remote ±1°C Accurate Digital Temperature
Sensors with SPI-Compatible Serial Interface
MAX6627/MAX6628
Typical Operating Characteristics
(V
CC
= +3.3V, T
A
= +25°C, unless otherwise noted.)
AVERAGE OPERATING CURRENT
vs. SUPPLY VOLTAGE
MAX6627/8 toc01
TEMPERATURE ERROR vs. TEMPERATURE
MAX6627/8 toc02
POWER-ON-RESET THRESHOLD
vs. TEMPERATURE
2.4
POWER-ON-RESET THRESHOLD (V)
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
-55 -30
-5
20
45
70
95
120 145
MAX6627/8 toc03
300
AVERAGE OPERATING CURRENT (μA)
250
200
150
100
MAX6628
50
0
3.0
3.5
4.0
4.5
5.0
3
2
TEMPERATURE ERROR (°C)
1
0
-1
-2
MAX6627
-3
T
A
= 0°C
T
A
= +25°C
T
A
= +70°C
2.6
MAX6627
5.5
-55 -30
-5
20
45
70
95
120 145
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE ERROR vs.
POWER-SUPPLY NOISE FREQUENCY
MAX6627/8 toc04
RESPONSE TO THERMAL SHOCK
MAX6627/8 toc05
TEMPERATURE ERROR
vs. DXP/DXN CAPACITANCE
MAX6627/8 toc06
12
10
TEMPERATURE ERROR (°C)
8
6
V
IN
= SQUARE WAVE
APPLIED TO V
CC
WITH NO
0.1μF CAPACITOR
5
125
100
75
50
25
0
TEMPERATURE ERROR (°C)
4
TEMPERATURE (°C)
3
V
IN
= 250mVp-p
4
2
0
10
100
1k
10k
100k
1M
10M 100M
FREQUENCY (Hz)
2
1
0
-2
0
2
4
6
TIME (s)
8
10
12
14
0
5000
10,000
15,000
20,000
CAPACITANCE (pF)
Pin Description
PIN
1
2
3
4
5
6
7
8
—
NAME
GND
DXN
DXP
V
CC
SCK
CS
SDO
N.C.
EP
Ground
Combined Current Sink and ADC Negative Input for Remote Diode. DXN is normally biased to a diode
voltage above ground.
Combined Current Source and ADC Positive Input for Remote Diode. Place a 2200pF capacitor between
DXP and DXN for noise filtering.
Supply Voltage Input. Bypass with a 0.1µF to GND.
SPI Clock Input
Chip Select Input. Pulling
CS
low initiates an idle state, but the SPI interface is still enabled. A rising edge
of
CS
initiates the next conversion.
SPI Data Output
No Connect. Internally not connected. Can be connected to GND for improved thermal conductivity.
Exposed Pad. Internally connected to GND. Connect to a large ground plane to maximize thermal
performance. Not intended as an electrical connection point.
FUNCTION
4
_______________________________________________________________________________________
Remote ±1°C Accurate Digital Temperature
Sensors with SPI-Compatible Serial Interface
Detailed Description
The MAX6627/MAX6628 remote digital thermometers
report the temperature of a remote sensor. The remote
sensor is a diode-connected transistor—typically, a
low-cost, easily mounted 2N3904 NPN type—that
replaces conventional thermistors or thermocouples.
The MAX6627/MAX6628 can also measure the die tem-
perature of other ICs, such as µPs or µCs, that contain
an on-chip, diode-connected transistor.
Remote accuracy is ±1°C when the temperature of the
remote diode is between 0°C and +125°C and the tem-
perature of the MAX6627/MAX6628 is +30°C. Data is
available as a 12-bit + sign word with 0.0625°C resolu-
tion. The operating range of the device extends from
-55°C to +125°C, although the architecture of the
device is capable of interpreting data up to +145°C.
The device itself should never exceed +125°C.
The MAX6627/MAX6628 are designed to work in con-
junction with an external µC or other intelligent device
serving as the master in thermostatic, process-control,
or monitoring applications. The µC is typically a power
management or keyboard controller, generating SPI
serial commands by “bit-banging” GPIO pins.
Two conversion rates are available; the MAX6627 con-
tinuously converts data every 0.5s, and the MAX6628
continuously converts data every 8s. Either device can
be read at any time and provide the data from the last
conversion. The slower version provides minimal power
consumption under all operating conditions. Or, by tak-
ing
CS
low, any conversion in progress is stopped, and
the rising edge of
CS
always starts a fresh conversion
and resets the interface. This permits triggering a con-
version at any time so that the power consumption of
the MAX6627 can be overcome, if needed. Both
devices operate with input voltages between +3.0V and
+5.5V and are specified between -55°C and +125°C.
The MAX6627/MAX6628 come in space-saving 8-pin
SOT23 and TDFN packages.
MAX6627/MAX6628
ADC Conversion Sequence
The device powers up as a free-running data converter
(Figure 1). The
CS
pin can be used for conversion con-
trol. The rising edge of
CS
resets the interface and
starts a conversion. The falling edge of
CS
stops any
conversion in progress, overriding the latency of the
part. Temperature data from the previous completed
conversion is available for read (Tables 1 and 2). It is
required to maintain
CS
high for a minimum of 320ms
to complete a conversion.
Idle Mode
Pull
CS
low to enter idle mode. In idle mode, the ADC is
not converting. The serial interface is still active and
temperature data from the last completed conversion
can still be read.
Power-On Reset
The POR supply voltage of the MAX6627/MAX6628 is
typically 1.6V. Below this supply voltage, the interface
is inactive and the data register is set to the POR state,
0.25s
CONVERSION
TIME
MAX6627
ADC CONVERTING
0.5s
SAMPLE
RATE
8s
SAMPLE
RATE
ADC IDLE
MAX6628
Figure 1. Free-Running Conversion Time and Rate Relationships
Table 1. Data Output Format
D15
Sign
D14
MSB
Data
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
LSB
Data
D2
Low
D1
High-Z
D0
High-Z
_______________________________________________________________________________________
5
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