MAX6696AEE+ Maxim Integrated Products, MAX6696AEE+ Datasheet - Page 8

• Manufacturer Part Number: MAX6696AEE+
• Description: IC SENSOR TEMP SMBUS 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX6696AEE+

• Function: Temp Monitoring System (Sensor)
• Topology: ADC, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 3 C
• Digital Output - Bus Interface: Serial (2-Wire)
• Digital Output - Number Of Bits: 10 bit + Sign
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

In this example, the effect of the series resistance and
the ideality factor partially cancel each other.
When the remote-sensing diode is a discrete transistor,
its collector and base must be connected together.
Table 1 lists examples of discrete transistors that are
appropriate for use with the MAX6695/MAX6696.
The transistor must be a small-signal type with a rela-
tively high forward voltage; otherwise, the A/D input
voltage range can be violated. The forward voltage at
the highest expected temperature must be greater than
0.25V at 10µA, and at the lowest expected tempera-
ture, the forward voltage must be less than 0.95V at
100µA. Large power transistors must not be used. Also,
ensure that the base resistance is less than 100 . Tight
specifications for forward current gain (50 < ß <150, for
example) indicate that the manufacturer has good
process controls and that the devices have consistent
V
Manufacturers of discrete transistors do not normally
specify or guarantee ideality factor. This is normally not
a problem since good-quality discrete transistors tend
to have ideality factors that fall within a relatively narrow
range. We have observed variations in remote tempera-
ture readings of less than 2 C with a variety of dis-
crete transistors. Still, it is good design practice to
verify good consistency of temperature readings with
several discrete transistors from any manufacturer
under consideration.
When sensing local temperature, these temperature
sensors are intended to measure the temperature of the
PC board to which they are soldered. The leads pro-
vide a good thermal path between the PC board traces
and the die. As with all IC temperature sensors, thermal
conductivity between the die and the ambient air is
poor by comparison, making air temperature measure-
ments impractical. Because the thermal mass of the PC
board is far greater than that of the MAX6695/
MAX6696, the device follows temperature changes on
the PC board with little or no perceivable delay.
When measuring the temperature of a CPU or other IC
with an on-chip sense junction, thermal mass has virtu-
ally no effect; the measured temperature of the junction
tracks the actual temperature within a conversion cycle.
When measuring temperature with discrete remote
transistors, the best thermal response times are
obtained with transistors in small packages (i.e., SOT23
or SC70). Take care to account for thermal gradients
between the heat source and the sensor, and ensure
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
8
BE
_______________________________________________________________________________________
characteristics.
Thermal Mass and Self-Heating
Discrete Remote Diodes
that stray air currents across the sensor package do
not interfere with measurement accuracy.
Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible. For local temperature mea-
surements, the worst-case error occurs when autocon-
verting at the fastest rate and simultaneously sinking
maximum current at the ALERT output. For example,
with V
sinking 1mA, the typical power dissipation is:
so assuming no copper PC board heat sinking, the
resulting temperature rise is:
Even under these worst-case circumstances, it is diffi-
cult to introduce significant self-heating errors.
The integrating ADC has good noise rejection for low-
frequency signals such as power-supply hum. In envi-
ronments with significant high-frequency EMI, connect
an external 2200pF capacitor between DXP_ and DXN.
Larger capacitor values can be used for added filter-
ing, but do not exceed 3300pF because it can intro-
duce errors due to the rise time of the switched current
source. High-frequency noise reduction is needed for
high-accuracy remote measurements. Noise can be
reduced with careful PC board layout as discussed in
the PC Board Layout section.
Standby mode reduces the supply current to less than
10µA by disabling the ADC. Enter hardware standby
(MAX6696 only) by forcing STBY low, or enter software
standby by setting the RUN/STOP bit to 1 in the config-
Table 1. Remote-Sensor Transistor
Manufacturers
Note: Discrete transistors must be diode connected (base
shorted to collector).
Central Semiconductor (USA)
Rohm Semiconductor (USA)
Samsung (Korea)
Siemens (Germany)
Zetex (England)
J-A
for the 16-pin QSOP package is about +120°C/W,
MANUFACTURER
CC
V
= 3.6V, a 4Hz conversion rate and ALERT
CC
T
2 2
500
.
mW
A
Low-Power Standby Mode
120
0 4
.
V
CMPT3904
SST3904
KST3904-TF
SMBT3904
FMMT3904CT-ND
C W
ADC Noise Filtering
1
/
mA
MODEL NO.
2 2
.
0 264
.
mW
C