ADT7473ARQZ-1R7 ON Semiconductor, ADT7473ARQZ-1R7 Datasheet - Page 24

• Manufacturer Part Number: ADT7473ARQZ-1R7
• Description: IC THERM MON FAN CTLR 16-QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7473ARQZ-1R7

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Fan Speed Counter, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• 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: +/- 0.5 C
• Digital Output - Bus Interface: Serial (3-Wire, 4-Wire)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Configuring the THERM Pin as Bidirectional
ADT7473/ADT7473−1 can optionally drive THERM low
as an output. When PROCHOT is bidirectional, THERM
can be used to throttle the processor by asserting
PROCHOT. The user can preprogram system−critical
thermal limits. If the temperature exceeds a thermal limit by
0.25°C, THERM asserts low. If the temperature is still above
the thermal limit on the next monitoring cycle, THERM
stays low. THERM remains asserted low until the
temperature is equal to or below the thermal limit. Because
the temperature for that channel is measured only once for
every monitoring cycle after THERM asserts, it is
guaranteed to remain low for at least one monitoring cycle.
Remote 1, local, or Remote 2 THERM temperature limits are
exceeded by 0.25°C. The THERM temperature limit registers
are at Register 0x6A, Register 0x6B, and Register 0x6C,
respectively. Setting Bit 5, Bit 6, and Bit 7 of Configuration
Register 5 (0x7C) makes THERM bidirectional for the
Remote 1, local, and Remote 2 temperature channels,
respectively. Figure 34 shows how the THERM pin asserts
low as an output in the event of a critical overtemperature.
the THERM temperature limit to –64°C or less in Offset 64
mode, or −128°C or less in twos complement mode; that is,
for THERM temperature limit values less than –63°C or
–128°C, respectively, THERM is disabled. THERM can
also be disabled by setting Bit 1 of Configuration Register 3
(0x78) to 0.
In addition to monitoring THERM as an input, the
The THERM pin can be configured to assert low, if the
An alternative method of disabling THERM is to program
(REGISTER 0x7A)
TIMER LIMIT
THERM
Figure 33. Functional Block Diagram of the ADT7473 THERM Monitoring Circuitry
728.32ms
364.16ms
182.08ms
91.04ms
45.52ms
22.76ms
2.914s
1.457s
0
1
2
3
4
5
6
COMPARATOR
http://onsemi.com
7
24
CLEARED
ON READ
7 6 5 4 3 2 1 0
Fan Drive Using PWM Control
(PWM) to control fan speed. This relies on varying the duty
cycle (or on/off ratio) of a square wave applied to the fan to
vary the fan speed. The external circuitry required to drive a
fan using PWM control is extremely simple. For 4−wire fans,
the PWM drive might need only a pullup resistor. In many
cases, the 4−wire fan PWM input has a built−in pullup
resistor.
a selection of low frequencies or a single high PWM
frequency. The low frequency options are usually used for
3−wire fans, while the high frequency option is usually used
with 4−wire fans.
TACH pins are not connected to a pullup supply greater than
3.6 V.
IN
Figure 34. Asserting THERM as an Output, Based on
LATCH
RESET
The ADT7473/ADT7473−1 uses pulse−width modulation
The ADT7473/ADT7473−1 PWM frequency can be set to
Note that care must be taken to ensure that the PWM or
THERM LIMIT
THERM LIMIT
TEMP
THERM
OUT
0.255C
1 = MASK
F4P BIT (BIT 5)
INTERRUPT STATUS
REGISTER 2
INTERRUPT MASK REGISTER 2
THERM TIMER CLEARED ON READ
Tripping THERM Limits
1.457s
182.08ms
2.914s
728.32ms
364.16ms
91.04ms
45.52ms
22.76ms
(REGISTER 0x75)
MONITORING
F4P BIT (BIT 5)
CYCLE
(REGISTER 0x79)
THERM TIMER
SMBALERT
THERM