ADT7462ACPZ-REEL ON Semiconductor, ADT7462ACPZ-REEL Datasheet - Page 47

• Manufacturer Part Number: ADT7462ACPZ-REEL
• Description: IC TEMP/VOLT MONITOR 32-LFCSP
• Manufacturer: ON Semiconductor

Specifications of ADT7462ACPZ-REEL

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, 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 ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 32-LFCSP
• Number Of Voltages Monitored: 1
• Monitored Voltage: 0.9 V to 12 V
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 3 V
• Supply Current (typ): 4000 uA
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

1/255 of the PWM period. In enhanced acoustics mode,
incrementing or decrementing by 1 changes the PWM
output by 1/255 × 100%.
Step 11—Ramp Rate for Acoustic Enhancement
found through system characterization after the thermal
optimization has been finished. The effect of each ramp rate
should be logged, if possible, to determine the best setting
for a given solution.
Enhanced Acoustics Register 1 (0x1A)
Bits [4:2] RR1 select the ramp rate for PWM1.
Bits [7:5] RR2 select the ramp rate for PWM2.
Enhanced Acoustics Register 2 (0x1B)
Bits [4:2] RR3 select the ramp rate for PWM3.
Bits [7:5] RR4 select the ramp rate for PWM4.
A ramp rate of 1 corresponds to one time slot, which is
The optimal ramp rate for acoustic enhancement can be
000 = 1 time slot = 35 seconds
001 = 2 time slots = 17.6 seconds
010 = 3 time slots = 11.8 seconds
011 = 5 time slots = 7 seconds
100 = 8 time slots = 4.4 seconds
101 = 12 time slots = 3 seconds
110 = 24 time slots = 1.6 seconds
111 = 48 time slots = 0.8 seconds
000 = 1 time slot = 35 seconds
001 = 2 time slots = 17.6 seconds
010 = 3 time slots = 11.8 seconds
011 = 5 time slots = 7 seconds
100 = 8 time slots = 4.4 seconds
101 = 12 time slots = 3 seconds
110 = 24 time slots = 1.6 seconds
111 = 48 time slots = 0.8 seconds
000 = 1 time slot = 35 seconds
001 = 2 time slots = 17.6 seconds
010 = 3 time slots = 11.8 seconds
011 = 5 time slots = 7 seconds
100 = 8 time slots = 4.4 seconds
101 = 12 time slots = 3 seconds
110 = 24 time slots = 1.6 seconds
111 = 48 time slots = 0.8 seconds
000 = 1 time slot = 35 seconds
001 = 2 time slots = 17.6 seconds
010 = 3 time slots = 11.8 seconds
011 = 5 time slots = 7 seconds
100 = 8 time slots = 4.4 seconds
101 = 12 time slots = 3 seconds
110 = 24 time slots = 1.6 seconds
111 = 48 time slots = 0.8 seconds
http://onsemi.com
47
it takes for the PWM output to ramp up from 0% to 100%
duty cycle for an instantaneous change in temperature. This
can be tested by putting the ADT7462 into manual mode and
changing the PWM output from 0% to 100% PWM duty
cycle. The PWM output takes 35 seconds to reach 100%
when a ramp rate of one time slot is selected.
duty cycle for enhanced acoustics mode. The ramp rate is set
to 48, which corresponds to the fastest ramp rate. Assume that
a new temperature reading is available every 115 ms. With
these settings, it takes approximately 0.76 seconds to go from
33% duty cycle to 100% duty cycle (full speed). Even though
the temperature increases very rapidly, the fan ramps up to
full speed gradually.
8 affects the control loop. The overall response of the fan is
slower. Because the ramp rate is reduced, it takes longer for
the fan to achieve full running speed. In this case, it takes
approximately 4.4 seconds for the fan to reach full speed.
Another way to view the ramp rates is to measure the time
Figure 77 shows remote temperature plotted against PWM
Figure 78 shows how changing the ramp rate from 48 to
Figure 77. Enhanced Acoustics Mode with Ramp
Figure 78. Enhanced Acoustics Mode with Ramp
140
120
100
120
100
80
60
40
20
80
60
40
20
0
0
0
0
R
R
TEMP
TEMP
(5C)
(5C)
Rate = 48
PWM CYCLE (%)
Rate = 8
TIME (s)
TIME (s)
PWM DUTY CYCLE (%)
4.4
0.76
120
100
80
60
40
20
0
140
120
100
80
60
40
20
0