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参数资料
| 型号： | MAX6639AEE+T |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 模拟信号调理 |
| 英文描述： | 2-Channel Temperature Monitor with Dual, Automatic, PWM Fan-Speed Controller |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, PDSO16 |
| 封装： | 0.150 INCH, 0.025 INCH PITCH, ROHS COMPLIANT, MO-137AB, QSOP-16 |
| 文件页数： | 24/24页 |
| 文件大小： | 393K |
| 代理商： | MAX6639AEE+T |
FANFAIL
The FANFAIL output asserts to indicate that one of the
fans has failed or is spinning slower than the required
speed. The MAX6639 detects fan fault depending on the
fan-control mode. In PWM mode, the MAX6639 pro-
duces a square wave with a duty cycle set by the value
written to the duty-cycle registers (26h and 27h). In this
mode, the MAX6639 signals a fan fault when the
tachometer count is greater than the maximum tachome-
ter count value stored in the appropriate register (22h
and 23h). After the MAX6639 asserts FANFAIL, the fan
with a tachometer fault goes to full speed for 2s in an
attempt to restart the fan and then returns to the original
duty-cycle settings. Reading the status register clears
the FANFAIL status bits and the output. The MAX6639
measures the fan speed again after 2s. The MAX6639
asserts FANFAIL if it detects the fan fault again.
In RPM mode (either automatic or manual), the
MAX6639 checks for fan failure only when the duty
cycle reaches 100%. It asserts FANFAIL when the
tachometer count is greater than twice the target
tachometer count. In manual RPM mode, registers 22h
and 23h store the target tachometer count value. In
automatic RPM mode, these registers store the maxi-
mum tachometer count.
Fan-Speed Control
The MAX6639 adjusts fan speed by controlling the duty
cycle of a PWM signal. This PWM signal then either
modulates the DC brushless fan’s power supply or dri-
ves a speed-control input on a fan that is equipped with
one. There are three speed-control modes: PWM, in
which the PWM duty cycle is directly programmed over
the SMBus; manual RPM, in which the desired
tachometer count is programmed into a register and
the MAX6639 adjusts its duty cycle to achieve the
desired tachometer count; and automatic RPM, in
which the tachometer count is adjusted based on a
programmed temperature profile.
The MAX6639 divides each PWM cycle into 120 time
slots. Registers 26h and 27h contain the current values
of the duty cycles for PWM1 and PWM2, expressed as
the effective time-slot length. For example, the PWM1
output duty cycle is 25% when register 26h reads 1Eh
(30/120).
PWM Control Mode
Enter PWM mode by setting bit 7 of the fan 1 or 2 con-
figuration 1 register (10h and 14h) to 1. In PWM control
mode, the MAX6639 generates PWM signals whose
duty cycles are specified by writing the desired values
to fan duty-cycle registers 26h and 27h. When a new
duty-cycle value is written into one of the fan duty-cycle
registers, the duty cycle changes to the new value at a
rate determined by the rate-of-change bits [6:4] in the
fan 1 or 2 configuration 1 register. The rate-of-change
of the duty cycle ranges from 000 (immediately
changes to the new programmed value) to 111
(changes by 1/120 every 4s). See Table 5 and the Fan
1 and 2 Configuration 1 (10h and 14h) section.
Manual RPM Control Mode
Enter manual RPM control mode by setting bits 2, 3,
and 7 of the fan 1 or 2 configuration 1 register (10h and
14h) to zero. In the manual RPM control mode, the
MAX6639 adjusts the duty cycle and measures the fan
speed. Enter the target tachometer count in register
22h for fan 1 and register 23h for fan 2. The MAX6639
compares the target tachometer count with the mea-
sured tachometer count and adjusts the duty cycle so
that the fan speed gradually approaches the target
tachometer count.
The first time manual RPM control mode is entered, the
initial PWM duty cycle is determined by the target
tachometer count:
where targetTACH is the value of the target tachometer
count in the target tach count register (22h or 23h).
If the initial duty-cycle value is over 120, the duty cycle
is 100%. If spin-up is enabled (bit 7 in registers 13h
and 17h) and the fan is not already spinning, the duty
cycle first goes to 100% and then goes to the initial
duty-cycle value. Every 2s, the MAX6639 counts the
fan’s period by counting the number of pulses stored in
registers 24h and 25h. If the count is different from the
target count, the duty cycle is adjusted.
If a nonzero rate-of-change is selected, the duty cycle
changes at the specified rate until the tachometer count
is within
±5 of the target. Then the MAX6639 gets into a
locked state and updates the duty cycle every 2s.
Automatic RPM Control Mode
In the automatic RPM control mode, the MAX6639 mea-
sures temperature, sets a target tachometer count
based on the measured temperature, and then adjusts
the duty cycle so the fan spins at the desired speed.
Enter this mode by setting bit 7 of the fan 1 or 2 config-
uration 1 register (10h and 14h) to zero and selecting
the temperature channel that controls the fan speed
using bits 2 and 3 of the configuration register.
In both RPM modes (automatic and manual), the
MAX6639 implements a low limit for the tachometer
Initial duty cycle
t
etTACH
arg
=
255
2
MAX6639
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
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| MAX6639ATE-T | 功能描述:马达/运动/点火控制器和驱动器 RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
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