TC649BEOA Microchip Technology, TC649BEOA Datasheet - Page 14

• Manufacturer Part Number: TC649BEOA
• Description: IC PWM FAN SPEED CTRLR SD 8-SOIC
• Manufacturer: Microchip Technology
• Type: Controller - PWM Fanr

Specifications of TC649BEOA

• Applications: Fan Controller, Brushless (BLDC)
• Number Of Outputs: 1
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Motor Type: PWM
• No. Of Outputs: 1
• Output Current: 5mA
• Output Voltage: 4.4V
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: SOIC
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Product: Fan / Motor Controllers / Drivers
• Operating Supply Voltage: 3 V to 5.5 V
• Supply Current: 400 uA
• Mounting Style: SMD/SMT
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Load: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

TC646B/TC648B/TC649B
For the TC646B and TC648B devices, an over-temper-
ature condition is indicated when the V
the V
is typically 20 mV higher than the V
has 80 mV of hysteresis). This indicates that maximum
cooling capacity has been reached (the fan is at full
speed) and that an overheating situation can occur.
When the voltage at the V
threshold voltage by the hysteresis value (V
the FAULT/OTF output will return to the high state (a
pull-up resistor is needed on the FAULT/OTF output).
For the TC646B/TC649B devices, a fan fault condition
is indicated when fan current pulses are no longer
detected at the SENSE pin. Pulses at the SENSE pin
indicate that the fan is spinning and conducting current.
If pulses are not detected at the SENSE pin for
32 PWM cycles, the 3-cycle diagnostic timer is fired.
This means that the V
cycles. If pulses are detected in this 3-cycle period, nor-
mal PWM operation is resumed and no fan fault is indi-
cated. If no pulses are detected in the 3-cycle period,
the start-up timer is activated and the V
driven high for 32 PWM cycles. If pulses are detected
during this time-frame, normal PWM operation is
resumed. If no pulses are detected during this time-
period, a fan fault condition exists and the FAULT
output is pulled low.
During a fan fault condition, the FAULT output will
remain low until the fault condition has been removed.
During this time, the V
uously to attempt to restart the fan and the SENSE pin
is monitored for fan pulses. If a minimum of 16 pulses
are detected at the SENSE input over a 32 cycle time-
period (one second for C
dition no longer exists. Therefore, The FAULT output is
released and the V
operation, as dictated by the V
If the V
a fan fault condition, the FAULT output will be released
and the V
the V
old and is above the V
through the normal start-up routine.
If, during a fan fault condition, the voltage at the V
drops below the V
TC649B device will continue to hold the FAULT line low
and drive the V
fault condition is then removed, the FAULT output will
be released and the TC646B/TC649B device will enter
auto-shutdown mode until the V
above the V
value (V
resume normal PWM mode operation.
The sink current capability of the FAULT output is listed
in the “Electrical Characteristics Table” of Section 1.0.
DS21755B-page 14
OTF
IN
IN
voltage then increases above the V
HAS
voltage is pulled below the V
threshold voltage (the V
OUT
AS
). The TC646B/TC649B device will then
output will be shutdown (V
voltage by the auto-shutdown hysteresis
OUT
output to 100% duty cycle. If the fan
OUT
AS
OUT
OUT
output returns to normal PWM
AS
voltage level, the TC646B/
F
IN
output is driven high contin-
= 1.0 µF), the fan fault con-
voltage, the device will go
output is high for 3 PWM
input falls below the V
IN
OTF
and V
IN
CMAX
voltage is brought
threshold voltage
SHDN
IN
AS
threshold and
input reaches
OUT
OUT
inputs.
level during
REL
OTF-HYS
output is
= 0V). If
thresh-
IN
OTF
pin
),
4.8
The SENSE input is an analog input used to monitor
the fan’s operation (the TC648B device does not incor-
porate the fan sensing feature). It does this by sensing
fan current pulses that represent fan rotation. When a
fan rotates, commutation of the fan current occurs as
the fan poles pass the armatures of the motor. The
commutation of the fan current makes the current
waveshape appear as pulses. There are two typical
current waveforms of brushless DC fan motors,
illustrated in Figures 4-6 and 4-7.
FIGURE 4-6:
And Positive Commutation Current.
FIGURE 4-7:
Commutation Pulses To Zero.
Sensing Fan Operation (SENSE)
Fan Current With DC Offset
Fan Current With
2003 Microchip Technology Inc.