ADT7463ARQZ ON Semiconductor, ADT7463ARQZ Datasheet - Page 26

• Manufacturer Part Number: ADT7463ARQZ
• Description: IC REMOTE THERMAL CTRLR 24-QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7463ARQZ

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Fan Speed Counter, 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: 24-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADT7463
Driving Two Fans from PWM3
Note that the ADT7463 has four TACH inputs available for fan
speed measurement, but only three PWM drive outputs. If a
fourth fan is being used in the system, it should be driven from
the PWM3 output in parallel with the third fan. Figure 31 shows
how to drive two fans in parallel using low cost NPN transistors.
Figure 32 is the equivalent circuit using the NDT3055L MOSFET.
Note that since the MOSFET can handle up to 3.5 A, it is
simply a matter of connecting another fan directly in parallel
with the first.
Care should be taken in designing drive circuits with transistors
and FETs to ensure that the PWM pins are not required to
source current and that they sink less than the 8 mA maximum
current specified on the data sheet.
Figure 32. Interfacing Two Fans in Parallel to the PWM3 Output Using a Single N-Channel MOSFET
Figure 31. Interfacing Two Fans in Parallel to the PWM3 Output Using Low Cost NPN Transistors
ADT7463
ADT7463
TACH4
TACH3
PWM3
PWM3
3.3V
3.3V
3.3V
3.3V
10k�
TYPICAL
10k�
TYPICAL
10k�
TYPICAL
Rev. 4 | Page 26 of 52 | www.onsemi.com
1k�
2.2k�
TACH
12V FAN
5V OR
3.3V
Q1
MMBT3904
–26–
TACH3
10�
+V
10�
Q1
NDT3055L
Driving up to Three Fans from PWM2
TACH measurements for fans are synchronized to particular
PWM channels, e.g., TACH1 is synchronized to PWM1. TACH3
and TACH4 are both synchronized to PWM3 so PWM3 can
drive 2 fans. Alternatively, PWM2 can be programmed to
synchronize TACH2, TACH3, and TACH4 to the PWM2 out-
put. This allows PWM2 to drive two or three fans. In this case,
the drive circuitry looks the same as shown in Figures 31 and 32.
The SYNC bit in Register 0x62 enables this function.
<4> (SYNC) ENHANCE ACOUSTICS REG 1 (0X62)
SYNC = 1 Synchronizes TACH2, TACH3, and TACH4
to PWM2.
Q2
MMBT2222
1N4148
TACH
12V
+V
Q3
MMBT2222
TACH4
5V OR 12V
FAN
REV. C