ADT7460ARQZ ON Semiconductor, ADT7460ARQZ Datasheet - Page 28

• Manufacturer Part Number: ADT7460ARQZ
• Description: IC REMOTE THRML/FAN CTRLR 16QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7460ARQZ

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 120°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 120°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 3 C
• Digital Output - Bus Interface: Serial (3-Wire)
• Maximum Operating Temperature: + 120 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADT7460
Table 29. SYNC : Enhance Acoustics Register 1 (Reg. 0x62)
Bit
<4>
Driving 2-Wire Fans
Figure 45 shows how a 2-wire fan may be connected to the
ADT7460. This circuit allows the speed of a 2-wire fan to be
measured, even though the fan has no dedicated TACH signal.
A series resistor, R
commutation pulses
ADT7460 through the 0.01 µF capacitor. On-chip signal con-
ditioning allows accurate monitoring of fan speed. The value of
R
on the current drawn by the fan. For fans drawing approximately
200 mA, a 2 Ω R
programmed as 40 mV. For fans that draw more current, such
as larger desktop or server fans, R
same programmed threshold. The smaller the threshold pro-
grammed the better, since more voltage is developed across the
SENSE
chosen depends on the programmed input threshold and
Mnemonic
SYNC
SENSE
SENSE
into a voltage. This is ac-coupled into the
value is suitable when the threshold is
, in the fan circuit converts the fan
Description
1 synchronizes TACH2, TACH3, and
TACH4 to PWM3.
Figure 44. Interfacing Two Fans in Par
Figure 43. Interfacing Two Fans in Parallel to the PWM
SENSE
may be reduced for the
ADT7460
ADT7460
TACH4
TACH3
PWM3
PWM3
3.3V
3.3V
3.3V
3.3V
10k Ω
TYPICAL
10k Ω
TYPICAL
10k Ω
TYPICAL
1kΩ
2.2kΩ
TACH
allel to the PWM
Rev. C | Page 28 of 52
3.3V
+V
TACH3
Q1
MMBT3904
Q1
NDT3055L
10Ω
10Ω
5V OR
12V FAN
3 Output Using a Single N-Channel M
fan and the fan spins faster. Figure 46 shows a typical plot of t
sensing waveform at a TACH/AIN pin. The most important
thing is that the voltage spikes (either negative going or positive
going) are more than 40 mV in amplitude. This allows fan speed
to be reliably determined.
3 Output Using Low Cost NPN Transistors
Q2
MMBT2222
MMBT2222
1N4148
TACH
ADT7460
Q3
TACH/AIN
+V
12V
PWM
5V OR
12V FAN
Figure 45. Drivin
TACH4
3.3V
10kΩ
TYPICAL
0.01µF
12V FAN
OSFET
5V OR
g a 2-Wire Fan
+V
Q1
NDT3055L
R
2Ω
TYPICAL
SENSE
1N4148
he