MAX1805MEE+ [MAXIM]
暂无描述;
| 型号： | MAX1805MEE+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 暂无描述 传感器 温度传感器 |
| 文件： | 总16页 (文件大小：224K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1766; Rev 0; 8/00
Multichannel Remote/Local
Temperature Sensor
________________General Description
____________________________Features
The MAX1668/MAX1805 are precise multichannel digi-
tal thermometers that report the temperature of all
remote sensors and their own packages. The remote
sensors are diode-connected transistors—typically low-
cost, easily mounted 2N3904 NPN types—that replace
conventional thermistors or thermocouples. Remote
accuracy is 3ꢀ° for multiple transistor manufacturers,
with no calibration needed. The remote channels can
also measure the die temperature of other I°s, such as
microprocessors, that contain an on-chip, diode-con-
nected transistor.
ꢀ Multichannel
4 Remote, 1 Local (MAX1668)
2 Remote, 1 Local (MAX1805)
ꢀ No Calibration Required
ꢀ SMBus 2-Wire Serial Interface
ꢀ Programmable Under/Overtemperature Alarms
ꢀ Supports SMBus Alert Response
ꢀ Accuracy
±2ꢀC (ꢁ60ꢀC to ꢁ100ꢀC, local)
±±ꢀC (-40ꢀC to ꢁ125ꢀC, local)
±±ꢀC (ꢁ60ꢀC to ꢁ100ꢀC, remote)
The 2-wire serial interface accepts standard System
Management Bus (SMBus™) Write Byte, Read Byte,
Send Byte, and Receive Byte commands to program the
alarm thresholds and to read temperature data. The data
format is 7 bits plus sign, with each bit corresponding to
1ꢀ°, in two’s-complement format.
ꢀ ±µA (typ) Standby Supply Current
ꢀ 700µA (max) Supply Current
ꢀ Small, 16-Pin QSOP Package
The MAX1668/MAX1805 are available in small, 16-pin
QSOP surface-mount packages.
________________________Applications
_______________Ordering Information
Desktop and Notebook
°omputers
°entral Office Telecom
Equipment
PART
TEMP. RANGE
-55ꢀ° to +125ꢀ°
-55ꢀ° to +125ꢀ°
PIN-PACKAGE
16 QSOP
MAX1668MEE
MAX1805MEE
LAN Servers
Test and Measurement
Multichip Modules
16 QSOP
Industrial °ontrols
Pin Configurations
Typical Operating Circuit
3V TO 5.5V
0.1µF
200Ω
TOP VIEW
V
STBY
DXP1
DXN1
1
2
3
4
5
6
7
8
16 GND
CC
10k EACH
15 STBY
14 SMBCLK
MAX1668
MAX1805
DXP2
DXP1
CLOCK
DATA
SMBCLK
2200pF
DXN2
MAX1668
MAX1805
13 SMBDATA
12 ALERT
11 ADD0
SMBDATA
ALERT
*
DXN1
(N.C.) DXP3
(N.C.) DXN3
(N.C.) DXP4
(N.C.) DXN4
INTERRUPT
TO µC
DXP4
DXN4
10 ADD1
2200pF
9
V
CC
*
ADD0 ADD1 GND
QSOP
( ) ARE FOR MAX1805.
*
DIODE-CONNECTED TRANSISTOR
SMBus is a trademark of Intel Corp.
†Patents Pending
________________________________________________________________ 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.
Multichannel Remote/Local
Temperature Sensor
ABSOLUTE MAXIMUM RATINGS
°°
DXP_, ADD_, STBY to GND........................-0.3V to (V
DXN_ to GND ........................................................-0.3V to +0.8V
SMB°LK, SMBDATA, ALERT to GND......................-0.3V to +6V
SMBDATA, ALERT °urrent .................................-1mA to +50mA
DXN_ °urrent...................................................................... 1mA
V
to GND..............................................................-0.3V to +6V
Operating Temperature Range .........................-55ꢀ° to +125ꢀ°
Junction Temperature......................................................+150ꢀ°
Storage Temperature Range.............................-65ꢀ° to +150ꢀ°
Lead Temperature (soldering, 10s) .................................+300ꢀ°
+ 0.3V)
°°
°ontinuous Power Dissipation (T = +70ꢀ°)
A
QSOP (derate 8.30mW/ꢀ° above +70ꢀ°).....................667mW
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
(V
= +3.3V, STBY = V , configuration byte = X0XXXX00, T = 0ꢀC to +125ꢀC, unless otherwise noted.)
°°
A
°°
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ADC AND POWER SUPPLY
Temperature Resolution (Note 1)
Monotonicity guaranteed
T = +60ꢀ° to +100ꢀ°
8
-2
Bits
ꢀ°
2
3
A
Initial Temperature Error,
Local Diode (Note 2)
T = 0ꢀ° to +125ꢀ°
A
-3
T = +60ꢀ° to +100ꢀ°
-3
3
R
Temperature Error, Remote Diode
(Notes 2 and 3)
ꢀ°
ꢀ°
T = -55ꢀ° to +125ꢀ°
R
-5
5
T = +60ꢀ° to +100ꢀ°
-2.5
-3.5
3.0
2.60
2.5
3.5
5.5
2.95
A
Temperature Error, Local Diode
(Notes 1 and 2)
Including long-term drift
T = 0ꢀ° to +85ꢀ°
A
Supply-Voltage Range
V
V
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
Power-On Reset Threshold (POR)
POR Threshold Hysteresis
V
V
input, disables A/D conversion, rising edge
2.8
50
°°
mV
V
, falling edge
1.3
1.8
50
2.3
°°
mV
SMBus static
3
5
10
12
Logic inputs
Standby Supply °urrent
forced to V
or GND
µA
°°
Hardware or software standby, SMB-
°LK at 10kHz
Average measured over 4s; logic inputs forced
or GND
Average Operating Supply °urrent
°onversion Time
400
700
µA
ms
V
°°
From stop bit to conversion complete (all channels)
High level (POR state)
260
70
7
320
100
10
380
130
13
Low level (POR state)
°onfiguration byte =
DXP_ forced to 1.5V
Remote-Diode Source °urrent
200
50
µA
X0XXXX10, high level
°onfiguration byte =
X0XXXX01, high level
DXN_ Source Voltage
0.7
V
Address Pin Bias °urrent
ADD0, ADD1; momentary upon power-on reset
160
µA
2
_______________________________________________________________________________________
Multichannel Remote/Local
Temperature Sensor
ELECTRICAL CHARACTERISTICS (continued)
(V
= +3.3V, STBY = V , configuration byte = X0XXXX00, T = 0ꢀC to +125ꢀC, unless otherwise noted.)
°°
A
°°
PARAMETER
SMBus INTERFACE
CONDITIONS
MIN
TYP
MAX
UNITS
Logic Input High Voltage
Logic Input Low Voltage
Logic Output Low Sink °urrent
2.2
V
V
STBY, SMB°LK, SMBDATA; V
= 3V to 5.5V
°°
0.8
STBY, SMB°LK, SMBDATA; V
= 3V to 5.5V
°°
6
mA
ALERT, SMBDATA forced to 0.4V
ALERT forced to 5.5V
ALERT Output High Leakage
°urrent
1
1
µA
Logic Input °urrent
Logic inputs forced to V
SMB°LK, SMBDATA
(Note 4)
or GND
-1
µA
pF
kHz
µs
°°
SMBus Input °apacitance
SMBus °lock Frequency
SMB°LK °lock Low Time
SMB°LK °lock High Time
SMBus Start-°ondition Setup Time
5
D°
4.7
4
100
t , 10% to 10% points
LOW
t
, 90% to 90% points
µs
HIGH
4.7
µs
SMBus Repeated Start-°ondition
Setup Time
t , 90% to 90% points
SU:STA
250
ns
SMBus Start-°ondition Hold Time
SMBus Stop-°ondition Setup Time
t
t
, 10% of SMBDATA to 90% of SMB°LK
, 90% of SMB°LK to 10% of SMBDATA
4
4
µs
µs
HD:STA
SU:STO
SMBus Data Valid to SMB°LK
Rising-Edge Time
t
t
, 10% or 90% of SMBDATA to 10% of SMB°LK
, slave receive (Note 5)
250
0
ns
ns
µs
SU:DAT
SMBus Data-Hold Time
HD:DAT
SMB°LK Falling Edge to SMBus
Data-Valid Time
Master clocking in data
1
ELECTRICAL CHARACTERISTICS
(V
= +5V, STBY = V , configuration byte = X0XXXX00, T = -55ꢀC to +125ꢀC, unless otherwise noted.) (Note 6)
°°
A
°°
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ADC AND POWER SUPPLY
Temperature Resolution
Monotonicity guaranteed
8
-2
Bits
ꢀ°
T
A
T
A
T
R
T
R
= +60ꢀ° to +100ꢀ°
2
3
Initial Temperature Error,
Local Diode (Note 2)
= -55ꢀ° to +125ꢀ°
= +60ꢀ° to +100ꢀ°
= -55ꢀ° to +125ꢀ°
-3
-3
3
Temperature Error, Remote Diode
(Notes 2 and 3)
ꢀ°
-5
5
Supply-Voltage Range
°onversion Time
4.5
260
5.5
380
V
From stop bit to conversion complete (both channels)
ms
_______________________________________________________________________________________
3
Multichannel Remote/Local
Temperature Sensor
ELECTRICAL CHARACTERISTICS (continued)
(V
= +5V, STBY = V , configuration byte = X0XXXX00, T = -55ꢀC to +125ꢀC, unless otherwise noted.) (Note 6)
°°
A
°°
PARAMETER
CONDITIONS
MIN
2.4
6
TYP
MAX
UNITS
SMBus INTERFACE
STBY, SMB°LK, SMBDATA
= 4.5V to 5.5V
Logic Input High Voltage
V
V
°°
Logic Input Low Voltage
0.8
V
STBY, SMB°LK, SMBDATA; V
= 4.5V to 5.5V
°°
Logic Output Low Sink °urrent
mA
ALERT, SMBDATA forced to 0.4V
ALERT Output High Leakage
°urrent
1
2
µA
µA
ALERT forced to 5.5V
Logic Input °urrent
Logic inputs forced to V
or GND
-2
°°
Note 1: Guaranteed by design, but not production tested.
Note 2: Quantization error is not included in specifications for temperature accuracy. For example, if the MAX1668/MAX1805
device temperature is exactly +66.7ꢀ°, the AD° may report +66ꢀ°, +67ꢀ°, or +68ꢀ° (due to the quantization error plus the
+1/2ꢀ° offset used for rounding up) and still be within the guaranteed 1ꢀ° error limits for the +60ꢀ° to +100ꢀ° tempera-
ture range. See Table 2.
Note 3: A remote diode is any diode-connected transistor from Table 1. T is the junction temperature of the remote diode. See
R
Remote Diode Selection for remote-diode forward-voltage requirements.
Note 4: The SMBus logic block is a static design that works with clock frequencies down to D°. While slow operation is possible, it
violates the 10kHz minimum clock frequency and SMBus specifications, and may monopolize the bus.
Note 5: Note that a transition must internally provide at least a hold time in order to bridge the undefined region (300ns max) of
SMB°LK’s falling edge t
HD:DAT.
Note 6: Specifications from -55ꢀ° to +125ꢀ° are guaranteed by design, not production tested.
__________________________________________Typical Operating Characteristics
(Typical Operating Circuit, V
= +5V, STBY = V , configuration byte = X0XXXX00, T = +25ꢀ°, unless otherwise noted.)
°° A
°°
TEMPERATURE ERROR
vs. SUPPLY NOISE FREQUENCY
TEMPERATURE ERROR
vs. PC BOARD RESISTANCE
TEMPERATURE ERROR
vs. TEMPERATURE
20
10
24
20
16
12
8
4
3
WITH V 0.1µF CAPACITOR REMOVED
CC
2200pF BETWEEN DXN_ AND DXP_
NPN (CMPT3904)
PNP (CMPT3906)
250mVp-p
2
PATH = DXP_ TO GND
0
1
0
100mVp-p
PATH = DXP_ TO V (5V)
CC
-10
-20
INTERNAL
4
-1
-2
0
0.1
1
10
100
1
10
100
-50 -30 -10 10 30 50 70 90 110
FREQUENCY (MHz)
LEAKAGE RESISTANCE (MΩ)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
Multichannel Remote/Local
Temperature Sensor
Typical Operating Characteristics (continued)
(Typical Operating Circuit, V
= +5V, STBY = V , configuration byte = X0XXXX00, T = +25ꢀ°, unless otherwise noted.)
°°
°°
A
TEMPERATURE ERROR
vs. DXP_ TO DXN_ CAPACITANCE
STANDBY SUPPLY CURRENT
vs. CLOCK FREQUENCY
TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
60
50
40
30
20
10
0
4
2
STBY = GND
SQUARE WAVE AC-COUPLED INTO DXN
2200pF BETWEEN DXN_ AND DXP_
100mVp-p
0
-2
-4
-6
-8
-10
50mVp-p
V
CC
= 5V
V
= 3.3V
CC
1
10
100
1000
0
10
20
30
40
50
60
0.1
1
10
100
1000
SMBCLK FREQUENCY (kHz)
DXP_ TO DXN_ CAPACITANCE (nF)
FREQUENCY (MHz)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
RESPONSE TO THERMAL SHOCK
160
140
120
100
80
125
100
75
50
25
0
STBY = GND
ADD0 = ADD1 = GND
60
40
ADD0 = ADD1 = HIGH-Z
16 QSOP IMMERSED IN
+115°C FLUORINERT BATH
20
0
0
1
2
3
4
5
-2
0
2
4
6
8
SUPPLY VOLTAGE (V)
TIME (s)
_______________________________________________________________________________________
5
Multichannel Remote/Local
Temperature Sensor
Pin Description
PIN
FUNCTION
MAX1668
MAX1805
NAME
5–8
N.°.
No °onnection. Not internally connected. May be used for P° board trace routing.
—
Supply Voltage Input, 3V to 5.5V. Bypass to GND with a 0.1µF capacitor. A 200Ω series
resistor is recommended but not required for additional noise filtering.
9
9
V
°°
°ombined °urrent Source and A/D Positive Input for remote-diode channel. Do not leave
DXP floating; tie DXP to DXN if no remote diode is used. Place a 2200pF capacitor
between DXP and DXN for noise filtering.
1, 3, 5, 7
2, 4, 6, 8
10
1, 3
2, 4
10
DXP_
DXN_
ADD1
°ombined °urrent Sink and A/D Negative Input. DXN is normally biased to a diode volt-
age above ground.
SMBus Address Select Pin (Table 8). ADD0 and ADD1 are sampled upon power-up.
Excess capacitance (>50pF) at the address pins when floating may cause address-
recognition problems.
11
16
12
13
14
16
11
12
13
14
GND
ADD0
Ground
SMBus Slave Address Select Pin
SMBus Alert (Interrupt) Output, Open Drain
SMBus Serial-Data Input/Output, Open Drain
SMBus Serial-°lock Input
ALERT
SMBDATA
SMB°LK
Hardware Standby Input. Temperature and comparison threshold data are retained in
standby mode. Low = standby mode, high = operate mode.
15
15
STBY
ADC and Multiplexer
_______________Detailed Description
The AD° is an averaging type that integrates over a
64ms period (each channel, typical), with excellent
noise rejection.
The MAX1668/MAX1805 are temperature sensors
designed to work in conjunction with an external micro-
controller (µ°) or other intelligence in thermostatic,
process-control, or monitoring applications. The µ° is
typically a power-management or keyboard controller,
generating SMBus serial commands by “bit-banging”
general-purpose input-output (GPIO) pins or via a dedi-
cated SMBus interface block.
The multiplexer automatically steers bias currents
through the remote and local diodes, measures their
forward voltages, and computes their temperatures.
Each channel is automatically converted once the con-
version process has started. If any one of the channels
is not used, the device still performs measurements on
these channels, and the user can ignore the results of
the unused channel. If any remote diode channel is
unused, tie DXP_ to DXN_ rather than leaving the pins
open.
These devices are essentially 8-bit serial analog-to-dig-
ital converters (AD°s) with sophisticated front ends.
However, the MAX1668/MAX1805 also contain a
switched current source, a multiplexer, an AD°, an
SMBus interface, and associated control logic (Figure
1). In the MAX1668, temperature data from the AD° is
loaded into five data registers, where it is automatically
compared with data previously stored in 10 over/under-
temperature alarm registers. In the MAX1805, tempera-
ture data from the AD° is loaded into three data
registers, where it is automatically compared with data
previously stored in six over/undertemperature alarm
registers.
The DXN_ input is biased at 0.65V above ground by an
internal diode to set up the analog-to-digital (A/D) inputs
for a differential measurement. The worst-case DXP_ to
DXN differential input voltage range is 0.25V to 0.95V.
Excess resistance in series with the remote diode caus-
es about +1/2ꢀ° error per ohm. Likewise, 200µV of offset
voltage forced on DXP_ to DXN causes about 1ꢀ° error.
6
_______________________________________________________________________________________
Multichannel Remote/Local
Temperature Sensor
Figure 1. MAX1668/MAX1805 Functional Diagram
_______________________________________________________________________________________
7
Multichannel Remote/Local
Temperature Sensor
A/D Conversion Sequence
Table 1. Remote-Sensor Transistor
Manufacturers
If a Start command is written (or generated automatical-
ly in the free-running autoconvert mode), all channels
are converted, and the results of all measurements are
available after the end of conversion. A BUSY status bit
in the status byte shows that the device is actually per-
forming a new conversion; however, even if the AD° is
busy, the results of the previous conversion are always
available.
MANUFACTURER
MODEL NUMBER
°entral Semiconductor (USA)
Motorola (USA)
°MPT3904
MMBT3904
National Semiconductor (USA)
Rohm Semiconductor (Japan)
Samsung (Korea)
MMBT3904
SST3904
Remote-Diode Selection
Temperature accuracy depends on having a good-qual-
ity, diode-connected small-signal transistor. Accuracy
has been experimentally verified for all of the devices
listed in Table 1. The MAX1668/MAX1805 can also
directly measure the die temperature of °PUs and other
I°s having on-board temperature-sensing diodes.
KST3904-TF
SMBT3904
Siemens (Germany)
Zetex (England)
FMMT3904°T-ND
Note: Transistors must be diode connected (base shorted to
collector).
The transistor must be a small-signal type, either NPN
or PNP, with a relatively high forward voltage; other-
wise, the A/D input voltage range can be violated. The
forward voltage must be greater than 0.25V at 10µA;
check to ensure this is true at the highest expected
temperature. The forward voltage must be less than
0.95V at 100µA; check to ensure this is true at the low-
est expected temperature. Large power transistors
don’t work at all. Also, ensure that the base resistance
is less than 100Ω. Tight specifications for forward-cur-
rent gain (+50 to +150, for example) indicate that the
manufacturer has good process controls and that the
devices have consistent VBE characteristics.
worst-case error occurs when sinking maximum current
at the ALERT output. For example, with ALERT sinking
1mA, the typical power dissipation is V
x 400µA plus
°°
0.4V x 1mA. Package theta J-A is about 150ꢀ°/W, so
with V = 5V and no copper P° board heat sinking,
°°
the resulting temperature rise is:
dT = 2.4mW x 150ꢀ°/W = 0.36ꢀ°
Even with these contrived circumstances, it is difficult
to introduce significant self-heating errors.
ADC Noise Filtering
The AD° is an integrating type with inherently good
noise rejection, especially of low-frequency signals
such as 60Hz/120Hz power-supply hum. Micropower
operation places constraints on high-frequency noise
rejection; therefore, careful P° board layout and proper
external noise filtering are required for high-accuracy
remote measurements in electrically noisy environ-
ments.
For heat-sink 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).
Thermal Mass and Self-Heating
Thermal mass can seriously degrade the MAX1668/
MAX1805’s effective accuracy. The thermal time con-
stant of the QSOP-16 package is about 140s in still air.
For the MAX1668/MAX1805 junction temperature to set-
tle to within +1ꢀ° after a sudden +100ꢀ° change
requires about five time constants or 12 minutes. The
use of smaller packages for remote sensors, such as
SOT23s, improves the situation. Take care to account
for thermal gradients between the heat source and the
sensor, and ensure that stray air currents across the
sensor package do not interfere with measurement
accuracy.
High-frequency EMI is best filtered at DXP_ and DXN_
with an external 2200pF capacitor. This value can be
increased to about 3300pF (max), including cable
capacitance. Higher capacitance than 3300pF intro-
duces errors due to the rise time of the switched cur-
rent source.
Nearly all noise sources tested cause additional error
measurements, typically by +1ꢀ° to +10ꢀ°, depending
on the frequency and amplitude (see Typical Operating
Characteristics).
PC Board Layout
1) Place the MAX1668/MAX1805 as close as practical
to the remote diode. In a noisy environment, such
Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible. For the local diode, the
8
_______________________________________________________________________________________
Multichannel Remote/Local
Temperature Sensor
as a computer motherboard, this distance can be
4 inches to 8 inches (typical) or more as long as the
worst noise sources (such as °RTs, clock genera-
tors, memory buses, and ISA/P°I buses) are avoid-
ed.
GND
10mils
10mils
10mils
DXP_
MINIMUM
10mils
2) Do not route the DXP_ to DXN_ lines next to the
deflection coils of a °RT. Also, do not route the
traces across a fast memory bus, which can easily
introduce +30ꢀ° error, even with good filtering.
Otherwise, most noise sources are fairly benign.
DXN_
GND
3) Route the DXP_ and DXN_ traces in parallel and in
close proximity to each other, away from any high-
voltage traces such as +12VD°. Leakage currents
from P° board contamination must be dealt with
carefully, since a 20MΩ leakage path from DXP_ to
ground causes about +1ꢀ° error.
Figure 2. Recommended DXP_/DXN_ PC Traces
• Use guard traces flanking DXP_ and DXN_ and con-
necting to GND.
• Place the noise filter and the 0.1µF V
bypass
°°
capacitors close to the MAX1668/MAX1805.
4) °onnect guard traces to GND on either side of the
DXP_ to DXN_ traces (Figure 2). With guard traces
in place, routing near high-voltage traces is no
longer an issue.
• Add a 200Ω resistor in series with V for best noise
°°
filtering (see Typical Operating Circuit).
Twisted-Pair and Shielded Cables
For remote-sensor distances longer than 8 inches, or in
particularly noisy environments, a twisted pair is recom-
mended. Its practical length is 6 feet to 12 feet (typical)
before noise becomes a problem, as tested in a noisy
electronics laboratory. For longer distances, the best
solution is a shielded twisted pair like that used for audio
microphones. For example, Belden #8451 works well for
distances up to 100 feet in a noisy environment. °onnect
the twisted pair to DXP_ and DXN_ and the shield to
GND, and leave the shield’s remote end unterminated.
5) Route through as few vias and crossunders as possi-
ble to minimize copper/solder thermocouple effects.
6) When introducing a thermocouple, make sure that
both the DXP_ and the DXN_ paths have matching
thermocouples. In general, P° board-induced ther-
mocouples are not a serious problem. A copper-sol-
der thermocouple exhibits 3µV/ꢀ°, and it takes
about 200µV of voltage error at DXP_ to DXN_ to
cause a +1ꢀ° measurement error. So, most para-
sitic thermocouple errors are swamped out.
Excess capacitance at DX_ _ limits practical remote sen-
sor distances (see Typical Operating Characteristics).
For very long cable runs, the cable’s parasitic capaci-
tance often provides noise filtering, so the 2200pF
capacitor can often be removed or reduced in value.
7) Use wide traces. Narrow ones are more inductive
and tend to pick up radiated noise. The 10mil
widths and spacings recommended in Figure 2
aren’t absolutely necessary (as they offer only a
minor improvement in leakage and noise), but try to
use them where practical.
°able resistance also affects remote-sensor accuracy;
1Ω series resistance introduces about +1/2ꢀ° error.
8) °opper can’t be used as an EMI shield, and only fer-
rous materials such as steel work well. Placing a cop-
per ground plane between the DXP_ to DXN_ traces
and traces carrying high-frequency noise signals
does not help reduce EMI.
Low-Power Standby Mode
Standby mode disables the AD° and reduces the sup-
ply-current drain to less than 12µA. Enter standby
mode by forcing the STBY pin low or via the RUN/STOP
bit in the configuration byte register. Hardware and
software standby modes behave almost identically: All
data is retained in memory, and the SMB interface is
alive and listening for reads and writes.
PC Board Layout Checklist
• Place the MAX1668/MAX1805 as close as possible
to the remote diodes.
• Keep traces away from high voltages (+12V bus).
• Keep traces away from fast data buses and °RTs.
• Use recommended trace widths and spacings.
• Place a ground plane under the traces.
Activate hardware standby mode by forcing the STBY
pin low. In a notebook computer, this line may be con-
nected to the system SUSTAT# suspend-state signal.
The STBY pin low state overrides any software conversion
command. If a hardware or software standby command
_______________________________________________________________________________________
9
Multichannel Remote/Local
Temperature Sensor
is received while a conversion is in progress, the conver-
sion cycle is truncated, and the data from that conversion
is not latched into either temperature reading register. The
previous data is not changed and remains available.
was previously selected by a Read Byte instruction. Use
caution with the shorter protocols in multimaster systems,
since a second master could overwrite the command
byte without informing the first master.
In standby mode, supply current drops to about 3µA.
At very low supply voltages (under the power-on-reset
threshold), the supply current is higher due to the
address pin bias currents. It can be as high as 100µA,
depending on ADD0 and ADD1 settings.
The temperature data format is 7 bits plus sign in two’s-com-
plement form for each channel, with each data bit represent-
ing 1ꢀ° (Table 2), transmitted MSB first. Measurements are
offset by +1/2ꢀ° to minimize internal rounding errors; for
example, +99.6ꢀ° is reported as +100ꢀ°.
SMBus Digital Interface
From a software perspective, the MAX1668/MAX1805
appear as a set of byte-wide registers that contain tem-
perature data, alarm threshold values, or control bits. A
standard SMBus 2-wire serial interface is used to read
temperature data and write control bits and alarm thresh-
old data. Each A/D channel within the devices responds
to the same SMBus slave address for normal reads and
writes.
Alarm Threshold Registers
Ten (six for MAX1805) registers store alarm threshold
data, with high-temperature (T
) and low-tempera-
HIGH
ture (T
) registers for each A/D channel. If either
LOW
measured temperature equals or exceeds the corre-
sponding alarm threshold value, an ALERT interrupt is
asserted.
The power-on-reset (POR) state of all T
registers is
HIGH
full scale (0111 1111, or +127ꢀ°). The POR state of all
T registers is 1100 1001 or -55ꢀ°.
LOW
The MAX1668/MAX1805 employ four standard SMBus
protocols: Write Byte, Read Byte, Send Byte, and Receive
Byte (Figure 3). The shorter Receive Byte protocol allows
quicker transfers, provided that the correct data register
Write Byte Format
S
ADDRESS
WR
ACK
COMMAND
ACK
DATA
ACK
P
7 bits
8 bits
8 bits
1
Slave Address: equiva-
lent to chip-select line of
a 3-wire interface
°ommand Byte: selects which
register you are writing to
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
Read Byte Format
S
ADDRESS
WR
ACK
COMMAND
ACK
S
ADDRESS
RD
ACK
DATA
///
P
7 bits
8 bits
7 bits
8 bits
Slave Address: equiva-
lent to chip-select line
°ommand Byte: selects
which register you are
reading from
Slave Address: repeated
due to change in data-
flow direction
Data Byte: reads from
the register set by the
command byte
Send Byte Format
Receive Byte Format
S
ADDRESS WR ACK COMMAND ACK
P
S
ADDRESS
RD
ACK DATA
8 bits
///
P
7 bits
8 bits
7 bits
Data Byte: This command only
works immediately following a
Read Byte. Reads data from the
register commanded by that last
Read Byte; also used for SMBus
Alert Response return address
°ommand Byte: sends com-
mand with no data
S = Start condition
P = Stop condition
Shaded = Slave transmission
/// = Not acknowledged
Figure 3. SMBus Protocols
10 ______________________________________________________________________________________
Multichannel Remote/Local
Temperature Sensor
Table 2. Data Format (Two’s Complement)
Table 3. Read Format for Alert Response
Address (0001100)
ROUNDED
TEMP.
(ꢀC)
DIGITAL OUTPUT
DATA BITS
MSB
TEMP.
(ꢀC)
BIT
NAME
FUNCTION
SIGN
0
LSB
7
+130.00
+127.00
+126.50
+126.00
+25.25
+0.50
+127
+127
+127
+126
+25
+1
111
111
111
111
001
000
000
000
000
000
111
111
110
110
100
100
011
011
1111
1111
1111
1110
1001
0001
0000
0000
0000
0000
1111
1111
0111
0110
1001
1001
1111
1111
ADD7
(MSB)
0
6
5
4
3
2
1
ADD6
ADD5
ADD4
ADD3
ADD2
ADD1
Provide the current
0
MAX1668/MAX1805 slave
address that was latched at POR
(Table 8)
0
0
0
+0.25
+0
0
+0.00
+0
0
0
1
Logic 1
-0.25
+0
0
(LSB)
-0.50
+0
0
Interrupts are generated in response to T
and T
LOW
-0.75
-1
1
HIGH
comparisons and when a remote diode is disconnected
(for continuity fault detection). The interrupt does not halt
automatic conversions; new temperature data continues
to be available over the SMBus interface after ALERT is
asserted. The interrupt output pin is open drain so that
devices can share a common interrupt line. The interrupt
rate can never exceed the conversion rate.
-1.00
-1
1
-25.00
-25.50
-54.75
-55.00
-65.00
-70.00
-25
-25
-55
-55
-65
-65
1
1
1
1
1
The interface responds to the SMBus Alert Response
address, an interrupt pointer return-address feature
(see Alert Response Address section). Prior to taking
corrective action, always check to ensure that an inter-
rupt is valid by reading the current temperature.
1
Diode Fault Alarm
There is a continuity fault detector at DXP_ that detects
whether the remote diode has an open-circuit condi-
tion. At the beginning of each conversion, the diode
fault is checked, and the status byte is updated. This
fault detector is a simple voltage detector; if DXP_ rises
Alert Response Address
The SMBus Alert Response interrupt pointer provides
quick fault identification for simple slave devices that
lack the complex, expensive logic needed to be a bus
master. Upon receiving an ALERT interrupt signal, the
host master can broadcast a Receive Byte transmission
to the Alert Response slave address (0001 100). Then
any slave device that generated an interrupt attempts
to identify itself by putting its own address on the bus
(Table 3).
above V
- 1V (typical) due to the diode current
°°
source, a fault is detected. Note that the diode fault
isn’t checked until a conversion is initiated, so immedi-
ately after power-on reset, the status byte indicates no
fault is present, even if the diode path is broken.
If any remote channel is shorted (DXP_ to DXN_ or
DXP_ to GND), the AD° reads 0000 0000 so as not to
The Alert Response can activate several different slave
devices simultaneously, similar to the I2° General °all.
If more than one slave attempts to respond, bus arbitra-
tion rules apply, and the device with the lower address
code wins. The losing device does not generate an
acknowledge and continues to hold the ALERT line low
until serviced (implies that the host interrupt input is
level sensitive). Successful reading of the alert
response address clears the interrupt latch.
trip either the T
or T
alarms at their POR set-
LOW
HIGH
tings. In applications that are never subjected to 0ꢀ° in
normal operation, a 0000 0000 result can be checked
to indicate a fault condition in which DXP_ is acciden-
tally short circuited. Similarly, if DXP_ is short circuited
to V , the AD° reads +127ꢀ° for all remote and local
°°
channels, and the device alarms.
ALERT
Interrupts
The ALERT interrupt output signal is latched and can
only be cleared by reading the Alert Response address.
______________________________________________________________________________________ 11
Multichannel Remote/Local
Temperature Sensor
Command Byte Functions
Manufacturer and Device ID Codes
The 8-bit command byte register (Table 4) is the master
index that points to the various other registers within the
MAX1668/MAX1805. The register’s POR state is 0000
0000, so that a Receive Byte transmission (a protocol
that lacks the command byte) that occurs immediately
after POR returns the current local temperature data.
Two ROM registers provide manufacturer and device
ID codes. Reading the Manufacturer ID returns 4Dh,
which is the AS°II code M (for Maxim). Reading the
device ID will return 03h for MAX1668, and 05h for
MAX1805. If Read Word 16-bit SMBus protocol is
Table 4. Command Byte Bit Assignments for MAX1668/MAX1805
REGISTER
COMMAND
POR STATE
FUNCTION
Read local temperature
RIT
RET1
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
10h
11h
12h
13h
14h
15h
16h
17h
18h
19h
1Ah
1Bh
1Ch
FEh
FFh
0000 0000*
0000 0000*
0000 0000*
0000 0000*
0000 0000*
0000 0000
0000 0000
0000 0000
0111 1111
1100 1001
0111 1111
1100 1001
0111 1111
1100 1001
0111 1111
1100 1001
0111 1111
1100 1001
N/A
Read remote DX1 temp.
Read remote DX2 temp.
Read remote DX3 temp.
Read remote DX4 temp.
Read status byte #1
RET2
RET3**
RET4**
RS1
RS2
Read status byte #2
RC
Read Configuration Byte
RIHL
Read local T
Read local T
limit
limit
HIGH
LOW
RILL
REHL1
RELL1
REHL2
RELL2
REHL3**
RELL3**
REHL4**
RELL4**
WC
Read remote DX1 T
Read remote DX1 T
Read remote DX2 T
Read remote DX2 T
Read remote DX3 T
Read remote DX3 T
Read remote DX4 T
Read remote DX4 T
limit
limit
limit
limit
limit
limit
limit
limit
HIGH
LOW
HIGH
LOW
HIGH
LOW
HIGH
LOW
Write configuration byte
WIHL
N/A
Write local T
Write local T
limit
limit
HIGH
LOW
WILL
N/A
WEHI1
WELL1
WEHI2
WELL2
WEHI3**
WELL3**
WEHI4**
WELL4**
MFG ID
DEV ID
N/A
Write remote DX1 T
Write remote DX1 T
Write remote DX2 T
Write remote DX2 T
Write remote DX3 T
Write remote DX3 T
Write remote DX4 T
Write remote DX4 T
limit
limit
limit
limit
limit
limit
limit
limit
HIGH
LOW
HIGH
LOW
HIGH
LOW
HIGH
LOW
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0100 1101
0000 0011 (0000 0101)
Read manufacture ID
Read device ID (for MAX1805)
*If the device is in hardware standby mode at POR, all temperature registers read 0°C.
**Not available for MAX1805.
12 ______________________________________________________________________________________
Multichannel Remote/Local
Temperature Sensor
employed (rather than the 8-bit Read Byte), the least
significant byte contains the data and the most signifi-
cant byte contains 00h in both cases.
Conversion Rate
The MAX1668/MAX1805 are continuously measuring
temperature on each channel. The typical conversion
rate is approximately three conversions/s (for both
devices). The resulting data is stored in the tempera-
ture data registers.
Configuration Byte Functions
The configuration byte register (Table 5) is used to
mask (disable) interrupts and to put the device in soft-
ware standby mode.
Slave Addresses
The MAX1668/MAX1805 appear to the SMBus as one
device having a common address for all ADC channels.
The device address can be set to one of nine different
values by pin-strapping ADD0 and ADD1 so that more
than one MAX1668/MAX1805 can reside on the same
bus without address conflicts (Table 8).
Status Byte Functions
The two status byte registers (Tables 6 and 7) indicate
which (if any) temperature thresholds have been
exceeded. The first byte also indicates whether the
ADC is converting and whether there is an open circuit
in a remote diode DXP_ to DXN_ path. After POR, the
normal state of all the flag bits is zero, assuming none
of the alarm conditions are present. The status byte is
cleared by any successful read of the status byte,
unless the fault persists. Note that the ALERT interrupt
latch is not automatically cleared when the status flag
bit is cleared.
The address pin states are checked at POR only, and
the address data stays latched to reduce quiescent
supply current due to the bias current needed for high-Z
state detection.
The MAX1668/MAX1805 also respond to the SMBus
Alert Response slave address (see the Alert Response
Address section).
When reading the status byte, you must check for inter-
nal bus collisions caused by asynchronous ADC timing,
or else disable the ADC prior to reading the status byte
(via the RUN/STOP bit in the configuration byte).
POR and Undervoltage Lockout
The MAX1668/MAX1805 have a volatile memory. To pre-
vent ambiguous power-supply conditions from corrupting
the data in memory and causing erratic behavior, a POR
To check for internal bus collisions, read the status
byte. If the least significant 7 bits are ones, discard the
data and read the status byte again. The status bits
LHIGH, LLOW, RHIGH, and RLOW are refreshed on the
SMBus clock edge immediately following the stop con-
dition, so there is no danger of losing temperature-relat-
ed status data as a result of an internal bus collision.
The OPEN status bit (diode continuity fault) is only
refreshed at the beginning of a conversion, so OPEN
data is lost. The ALERT interrupt latch is independent of
the status byte register, so no false alerts are generated
by an internal bus collision.
voltage detector monitors V
CC
and clears the memory if
falls below 1.8V (typical, see Electrical Characteristics
CC
V
table). When power is first applied and V
rises above
CC
1.85V (typical), the logic blocks begin operating, although
reads and writes at V
levels below 3V are not recom-
CC
mended. A second V comparator, the ADC UVLO com-
CC
parator, prevents the ADC from converting until there is
sufficient headroom (V = 2.8V typical).
CC
Power-Up Defaults
If the THIGH and TLOW limits are close together, it’s
possible for both high-temp and low-temp status bits to
be set, depending on the amount of time between sta-
tus read operations (especially when converting at the
fastest rate). In these circumstances, it’s best not to rely
on the status bits to indicate reversals in long-term tem-
perature changes and instead use a current tempera-
ture reading to establish the trend direction.
• Interrupt latch is cleared.
• Address select pins are sampled.
• ADC begins converting.
• Command byte is set to 00h to facilitate quick
remote Receive Byte queries.
• T
and T
registers are set to max and min
LOW
HIGH
limits, respectively.
______________________________________________________________________________________ 13
Multichannel Remote/Local
Temperature Sensor
Table 5. Configuration Byte Bit Assignments
BIT
NAME
POR
FUNCTION
Masks all ALERT interrupts when high.
7 (MSB)
MASKALL
0
Standby mode control bit. If high, the device immediately stops converting and
enters stand-by mode. If low, the device converts.
6
RUN/STOP
0
5
4
3
2
MASK4*
MASK3*
MASK2
MASK1
0
0
0
0
Masks remote DX4 interrupts when high.
Masks remote DX3 interrupts when high.
Masks remote DX2 interrupts when high.
Masks remote DX1 interrupts when high.
Medium/low-bias control bit. High = low bias, low = medium bias. IBIAS0 must be
low.
0
1
IBIAS1
IBIAS0
0
0
High-bias control bit. High bias on DXP_ when high. Overrides IBIAS1.
*Not available for MAX1805.
Table 6. Status Byte Bit 1 Assignments
BIT
NAME
BUSY
LHIGH†
LLOW†
OPEN†
ALARM†
N/A
FUNCTION
A high indicates that the ADC is busy converting.
7 (MSB)
6
5
4
3
2
1
0
A high indicates that the local high-temperature alarm has activated.
A high indicates that the local low-temperature alarm has activated.
A high indicates one of the remote-diode continuity (open-circuit) faults
A high indicates one of the remote-diode channels has over/undertemperature alarm.
N/A
N/A
N/A
N/A
N/A
†These flags stay high until cleared by POR, or until the status byte register is read.
Table 7. Status Byte 2 Bit Assignments
BIT
NAME
RLOW1
RHIGH1
RLOW2
RHIGH2
RLOW3*
RHIGH3*
RLOW4*
RHIGH4*
FUNCTION
7 (MSB)
A high indicates that the DX1 low-temperature alarm has activated.
A high indicates that the DX1 high-temperature alarm has activated.
A high indicates that the DX2 low-temperature alarm has activated.
A high indicates that the DX2 high-temperature alarm has activated.
A high indicates that the DX3 low-temperature alarm has activated.
A high indicates that the DX3 high-temperature alarm has activated.
A high indicates that the DX4 low-temperature alarm has activated.
A high indicates that the DX4 high-temperature alarm has activated.
6
5
4
3
2
1
0
Note: All flags in this byte stay high until cleared by POR or until the status byte is read.
*Not available for MAX1805.
14 ______________________________________________________________________________________
Multichannel Remote/Local
Temperature Sensor
Table 8. Slave Address Decoding (ADD0
and ADD1)
ADD0
ADD1
GND
ADDRESS
0011 000
0011 001
0011 010
0101 001
0101 010
0101 011
1001 100
1001 101
1001 110
GND
GND
High-Z
GND
V
CC
High-Z
High-Z
High-Z
GND
High-Z
V
CC
V
CC
V
CC
V
CC
GND
High-Z
V
CC
Note: High-Z means that the pin is left unconnected and floating.
A
B
C
D
E
F
G
H
I
J
K
t
t
HIGH
LOW
SMBCLK
SMBDATA
t
t
t
t
t
BUF
SU:STA HD:STA
SU:DAT
SU:STO
A = START CONDITION
E = SLAVE PULLS SMBDATA LINE LOW
I = ACKNOWLEDGE CLOCK PULSE
J = STOP CONDITION
K = NEW START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
Figure 4. SMBus Read Timing Diagram
A
B
C
D
E
F
G
H
I
J
K
L
M
t
t
HIGH
LOW
SMBCLK
SMBDATA
t
t
t
t
HD:DAT
HD:STA
SU:STA
SU:DAT
t
t
SU:STO
BUF
A = START CONDITION
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
Figure 5. SMBus Write Timing Diagram
______________________________________________________________________________________ 15
Multichannel Remote/Local
Temperature Sensor
________________________________________________________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.
16 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 2000 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
相关型号：
MAX1805MEE+T
Serial Switch/Digital Sensor, 8 Bit(s), 3Cel, Rectangular, 16 Pin, Surface Mount, 0.150 INCH, QSOP-16
MAXIM
MAX1805MEE-T
Serial Switch/Digital Sensor, 8 Bit(s), 3Cel, Rectangular, 16 Pin, Surface Mount, 0.150 INCH, QSOP-16
MAXIM
MAX1806EUA08+
Fixed/Adjustable Positive LDO Regulator, 0.8V Min, 4.5V Max, CMOS, PDSO8, POWER, MICRO MAX PACKAGE-8
MAXIM
MAX1806EUA08-T
Fixed/Adjustable Positive LDO Regulator, 0.8V Min, 4.5V Max, CMOS, PDSO8, POWER, MICRO MAX PACKAGE-8
MAXIM
MAX1806EUA15+T
Fixed/Adjustable Positive LDO Regulator, 0.8V Min, 4.5V Max, CMOS, PDSO8, POWER, MICRO MAX PACKAGE-8
MAXIM
©2020 ICPDF网 联系我们和版权申明