19-2117; Rev 0; 7/01
Dual Remote/Local Temperature Sensors and
Four-Channel Voltage Monitors
General Description
The MAX6655/MAX6656 are precise voltage and tem-
perature monitors. The digital thermometer reports the
temperature of two remote sensors and its own die tem-
perature. The remote sensors are diode-connected
transistors—typically a low-cost, easily mounted
2N3906 PNP type—that replace conventional thermis-
tors or thermocouples. Remote accuracy is ±1°C for
multiple transistor manufacturers with no calibration
necessary. The remote channels can also measure the
die temperature of other ICs, such as microprocessors,
that contain a substrate-connected PNP with its collec-
tor grounded and its base and emitter available for tem-
perature-sensing purposes. The temperature is
digitized with 11-bit resolution.
The MAX6655/MAX6656 also measure their own supply
voltage and three external voltages with 8-bit resolution.
Each voltage input’s sensitivity is set to give approxi-
mately 3/4-scale output code when the input voltage is
at its nominal value. The MAX6655 operates at +5V
supply and its second voltage monitor is 3.3V. The
MAX6656 operates on a +3.3V supply and its second
voltage monitor is 5V.
The 2-wire serial interface accepts standard SMBus™
Write Byte, Read Byte, Send Byte, and Receive Byte
commands to program the alarm thresholds and to
read data. The MAX6655/MAX6656 also provide
SMBus alert response and timeout functions. The
MAX6655/MAX6656 measure automatically and
autonomously, with the conversion rate programmable.
The adjustable rate allows the user to control the supply
current.
In addition to the SMBus
ALERT
output, the MAX6655/
MAX6656 feature an
OVERT
output, which is used as a
temperature reset that remains active only while the
temperature is above the maximum temperature limit.
The
OVERT
output is optimal for fan control or for sys-
tem shutdown.
o
Three Temperature Channels
Two Remote PN Junctions
One Local Sensor
o
Four Voltage Channels
+12V, +5V, +3.3V, +2.5V
Three External Monitors
One Internal Supply Monitor
o
11-Bit, 0.125°C Resolution
o
High Accuracy: ±1°C Over +60°C to +100°C
Temperature Range
o
Programmable Under/Over-Threshold Alarms
o
Programmable Power-Saving Mode
o
No Calibration Required
o
SMBus/I
2
C™-Compatible Interface
o
OVERT
Output for Fan Control and System
Shutdown
Features
MAX6655/MAX6656
Ordering Information
PART
MAX6655MEE
MAX6656MEE
TEMP. RANGE
-55°C to +125°C
-55°C to +125°C
PIN-PACKAGE
16 QSOP
16 QSOP
Typical Application Circuit appears at end of data sheet.
Pin Configuration
TOP VIEW
V
CC
1
DXP1 2
DXN1 3
ADD0 4
ADD1 5
DXP2 6
DXN2 7
GND 8
16 STBY
15 SMBCLK
14 OVERT
Applications
Notebooks
Thin Clients
Servers
Workstations
Communication Equipment
Desktop PC
SMBus is a trademark of Intel Corp.
I
2
C is a trademark of Philips Corp.
MAX6655
MAX6656
13 SMBDATA
12 ALERT
11 V
IN2
10 V
IN1
9
V
IN3
QSOP
________________________________________________________________
Maxim Integrated Products
1
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.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
