TC649EUA Microchip Technology, TC649EUA Datasheet - Page 15

• Manufacturer Part Number: TC649EUA
• Description: IC PWM FAN SPD CTRLR SD 8-MSOP
• Manufacturer: Microchip Technology
• Type: Controller - PWM Fanr

Specifications of TC649EUA

• 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-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Motor Type: PWM
• No. Of Outputs: 1
• Output Current: 5mA
• Output Voltage: 4.4V
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: MSOP
• 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

The SENSE pin senses positive voltage pulses that
have an amplitude of 70 mV (typical value). Each time
a pulse is detected, the missing pulse detector timer
(t
detector timer reaches the time for 32 cycles, the loop
for diagnosing a fan fault is engaged (diagnostic timer,
then the start-up timer).
Both of the fan current waveshapes shown in Figures
shown in Figure 4-8.
FIGURE 4-8:
Current.
The fan current flowing through R
voltage that is proportional to the current. The C
capacitor removes any DC portion of the voltage
across R
portion to the SENSE pin of the TC646B/TC649B
devices.
The R
that the voltage pulse provided to the SENSE pin is
70 mV (typical) in amplitude. Be sure to check the
sense pulse amplitude over all operating conditions
(duty cycles) as the current pulse amplitude will vary
with duty cycle. See Section 5.0, “Applications Informa-
tion”, for more details on selecting values for R
and C
Key features of the SENSE pin circuitry are an initial
blanking period after every V
pulse blanker.
The TC646B/TC649B sense circuitry has a blanking
period that occurs at the turn-on of each V
During this blanking period, the sense circuitry ignores
any pulse information that is seen at the SENSE pin
input. This stops the TC646B/TC649B device from
falsely sensing a current pulse that is due to the fan
drive device turn-on.
4-6 and 4-7 can be sensed with the sensing scheme
MP
2003 Microchip Technology Inc.
) is reset. As previously stated, if the missing pulse
SENSE
SENSE
TC64XB
GND
SENSE
SENSE
V
.
OUT
and C
and presents only the voltage pulse
SENSE
(0.1 µF typical)
Sensing Scheme For Fan
C
SENSE
values need to be selected so
OUT
R
ISO
pulse and an initial
SENSE
R
SENSE
generates a
OUT
FAN
SENSE
SENSE
pulse.
TC646B/TC648B/TC649B
The initial pulse blanker is also implemented to stop
false sensing of fan current pulses. When a fan is in a
locked rotor condition, the fan current no longer com-
mutates, it simply flows through one fan winding and is
a DC current. When a fan is in a locked rotor condition
and the TC646B/TC649B device is in PWM mode, it
will see one current pulse each time the V
turned on. The initial pulse blanker allows the
TC646B/TC649B device to ignore this pulse and
recognize that the fan is in a fault condition.
4.9
The behavioral algorithms for the TC646B/TC649B
and TC648B devices are shown in Figure 4-9 and
Figure 4-10, respectively.
The behavioral algorithms show the step-by-step deci-
sion-making process for the fan speed controller oper-
ation. The TC646B and TC649B devices are very
similar with one exception: the TC649B device does
not implement the over-temperature portion of the
algorithm.
Behavioral Algorithms
DS21755B-page 15
OUT
output is