ADM1024ARUZ ON Semiconductor, ADM1024ARUZ Datasheet - Page 16

• Manufacturer Part Number: ADM1024ARUZ
• Description: IC MONITOR SYS TEMP/VOLT 24TSSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1024ARUZ

• Applications: PC's, PDA's
• Interface: Serial
• Voltage - Supply: 2.8 V ~ 5.5 V
• Package / Case: 24-TSSOP
• Mounting Type: Surface Mount
• Temperature Sensor Function: Temp Sensor
• Output Type: Digital
• Package Type: TSSOP
• Operating Temperature (min): 0C
• Operating Temperature (max): 100C
• Operating Temperature Classification: Commercial
• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (max): 5.5V
• Full Temp Accuracy: +/- 2 C , +/- 3 C
• Digital Output - Bus Interface: SMBus
• Digital Output - Number Of Bits: 10 bit
• Supply Voltage (max): 12 V
• Supply Voltage (min): 2.5 V
• Maximum Operating Temperature: + 100 C
• Minimum Operating Temperature: 0 C
• Supply Current: 1.4 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Fault−Tolerant Fan Control
capability that can override the setting of the analog output
and force it to maximum to give full fan speed in the event
of a critical overtemperature problem even if, for some
reason, this has not been handled by the system software.
analog output to FFh if any one of them is exceeded for three
or more consecutive measurements. Two of these limits are
programmable by the user and two are hardware limits
intended as must not exceed limits that cannot be changed.
The analog output will be forced to FFh if:
the limit programmed into register address 13hp;
exceeds the limit programmed into address 14h;
70°C, which is hardware programmed into a read−only
register at address 17h;
exceeds 85°C, which is hardware programmed into a
read−only register at address 18h.
triggered, it will return to normal operation only after three
consecutive measurements that are 5 degrees lower than
each of the above limits.
THERM pin (Pin 2) low.
by the user. Obviously, these limits should not exceed the
hardware values in Registers 17h and 18h, as they would
have no effect. The power−on default values of these
registers are the same as the two hardware registers, 70°C
and 85°C, respectively, so there is no need to program them
if these limits are acceptable.
defaults are acceptable, the values in these registers can be
locked by writing a 1 to Bits 1 and 2 of Configuration
Register 2 (address 4Ah). This prevents any unauthorized
tampering with the limits. These lock bits can only be
written to 1 and can only be cleared by power−on reset or by
The ADM1024 incorporates a fault−tolerant fan control
There are four temperature set points that will force the
The temperature measured by the on−chip sensor exceeds
The temperature measured by either of the remote sensors
The temperature measured by the on−chip sensor exceeds
The temperature measured by either of the remote sensors
Once the hardware override of the analog output is
The analog output can also be forced to FFh by pulling the
The limits in Registers 13h and 14h can be programmed
Once these registers have been programmed, or if the
or:
or:
or:
6. In all these circuits, the output transistor must have
7. If the fan motor produces a large back EMF when
an I
and be capable of dissipating power due to the
voltage dropped across it when the fan is not
operating at full speed.
switched off, it may be necessary to add clamp
diodes to protect the output transistors in the event
that the output goes very quickly from full scale to
zero.
CMAX
greater than the maximum fan current,
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16
taking the RESET pin low, so registers 13h and 14h cannot
be written to again unless the device is powered off, then on.
Layout and Grounding
a clean ground. A separate, low impedance ground plane for
analog ground, which provides a ground point for the
voltage dividers and analog components, will provide best
performance but is not mandatory.
10 mF (electrolytic or tantalum) and 0.1 mF (ceramic) bypass
capacitors connected between Pin 9 and ground, should also
be located as close as possible to the ADM1024.
Fan Inputs
speed inputs by programming Bits 0 and 1 of the Channel
Mode Register. The power−on default for these bits is all
zeros, which makes Pins 5 and 6 fan inputs.
slow rise and fall times typical of fan tachometer outputs.
The maximum input signal range is 0 to V
that these inputs are supplied from fan outputs that exceed
0 V to 6.5 V, either resistive attenuation of the fan signal or
diode clamping must be included to keep inputs within an
acceptable range.
tachometer outputs.
it can be directly connected to the fan input, as shown in
Figure 25.
voltage greater than 6.5 V), the fan output can be clamped
with a Zener diode, as shown in Figure 26. The Zener
voltage should be chosen so it is greater than V
than 6.5 V, allowing for the voltage tolerance of the Zener.
A value of between 3.0 V and 5.0 V is suitable.
Analog inputs will provide best accuracy when referred to
The power supply bypass, the parallel combination of
Pins 5 and 6 may be configured as analog inputs or fan
Signal conditioning in the ADM1024 accommodates the
Figure 25 to Figure 28 show circuits for most common fan
If the fan tachometer output has a resistive pullup to V
If the fan output has a resistive pullup to 12 V (or other
Figure 26. Fan with Tach. Pullup to Voltage >6.5 V
12V
Figure 25. Fan with Tach Pullup to +V
12V
PULLUP
(e.g., 12 V) Clamped with Zener Diode
PULLUP
4.7k
4.7k
TYP
TYP
W
W
*
CHOOSE ZD1 VOLTAGE APPROXIMATELY 0.8 y V
TACH
OUTPUT
TACH
OUTPUT
FAN1 OR
FAN1 OR
FAN2
ZD1
ZENER
FAN2
*
160k
160k
W
V
CC
W
CC
V
FAN SPEED
CC
FAN SPEED
. In the event
COUNTER
COUNTER
CC
IH
but less
CC
CC
.
,