TC649BEOA Microchip Technology, TC649BEOA Datasheet - Page 13

• 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

For the TC646B, TC648B and TC649B devices, the V
pin is also used as the shutdown pin. The V
V
trical Characteristics Table” of Section 1.0. If the V
voltage is pulled below the V
will shut down (V
FAULT/OTF pin is inactive). If the voltage on the V
then rises above the release threshold (V
device will go through a power-up sequence (assuming
that the V
the V
the “Behavioral Algorithm Flowcharts” of Section 4.9.
FIGURE 4-4:
Cycle (Typical).
4.5
For the TC646B, TC648B and TC649B devices, pin 3
is the V
threshold voltage.
The auto-shutdown function provides a way to set a
threshold voltage (temperature) at which the fan will be
shut off. This way, if the temperature in the system
reaches a threshold at which the fan(s) no longer needs
to operate, the fan can be shutdown automatically.
The voltage range for the V
voltage range for the V
age at the V
voltage at the V
the V
has been reached), the V
a low state). In auto-shutdown, the FAULT/OTF output
is inactive (high-impedance). Auto-shutdown mode is
exited when the V
by the auto-shutdown hysteresis voltage (V
exiting auto-shutdown mode, the start-up timer is
triggered and the device returns to normal operation.
4.6
The V
the base of a transistor or the gate of a MOSFET. The
V
base current or the gate voltage of the external drive
device to its final value.
REL
OUT
2003 Microchip Technology Inc.
100
AS
AS
90
80
70
60
50
40
30
20
10
threshold voltages are characterized in the “Elec-
OUT
output is designed to be able to quickly raise the
0
AS
1
pin). The power-up sequence is shown later in
pin (signifying that the threshold temperature
Auto-Shutdown Mode (V
V
IN
pin and is used for setting the auto-shutdown
output is a digital output designed for driving
OUT
1.2
AS
voltage is also higher than the voltage at
pin is set in this range so that when the
IN
Output (PWM Output)
1.4
OUT
IN
pin decreases below the voltage at
1.6
voltage exceeds the V
IN
output goes to a low state, the
V
IN
pin (1.20V to 2.60V). The volt-
OUT
1.8
V
Voltage vs. PWM Duty
IN
SHDN
AS
output is shut off (goes to
(V)
2
pin is the same as the
threshold, the device
2.2
2.4
AS
HAS
AS
)
2.6
SHDN
REL
). Upon
voltage
), the
IN
IN
2.8
and
pin
pin
IN
TC646B/TC648B/TC649B
When the device is in shutdown/auto-shutdown mode,
the V
varied from 0% (full off) to 100% duty cycle (full on). As
previously discussed, the duty cycle of the V
is controlled via the V
nated based on the V
A base current-limiting resistor is required when using
a transistor as the external drive device in order to limit
the amount of drive current that is drawn from the V
output.
The V
of an external MOSFET. One concern when doing this,
though, is that the fast turn-off time of the fan drive
MOSFET can cause a problem because the fan motor
looks like an inductor. When the MOSFET is turned off
quickly, the current in the fan wants to continue to flow
in the same direction. This causes the voltage at the
drain of the MOSFET to rise. If there aren’t any clamp
diodes internal to the fan, this voltage can rise above
the drain-to-source voltage rating of the MOSFET. For
this reason, an external clamp diode is suggested. This
is shown in Figure 4-5.
FIGURE 4-5:
4.7
The FAULT/OTF output is an open-drain, active-low
output. For the TC646B and TC649B devices, pin 6 is
labeled as the FAULT output and indicates when a fan
fault condition has occurred. For the TC646B device,
the FAULT output also indicates when an over-temper-
ature (OTF) condition has occurred. For the TC648B
device, pin 6 is the OTF output that indicates an over-
temperature (OTF) condition has occurred.
OUT
OUT
Clamp Diode
FAULT/OTF Output
output is actively held low. The output can be
output can be directly connected to the gate
V
Q
OUT
1
: N-Channel MOSFET
IN
AS
Clamp Diode for Fan.
input voltage and can be termi-
voltage.
FAN
GND
DS21755B-page 13
R
Q
SENSE
1
OUT
output
OUT