TC654EUN Microchip Technology, TC654EUN Datasheet - Page 25

• Manufacturer Part Number: TC654EUN
• Description: IC PWM FAN SPEED CTRLR 10-MSOP
• Manufacturer: Microchip Technology
• Type: High Speed PWM Controllerr

Specifications of TC654EUN

• Number Of Outputs: 1
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Applications: Fan Controller, Brushless (BLDC)
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Output Current: 5 mA (Min)
• Operating Supply Voltage: 3 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Motor Type: PWM
• No. Of Outputs: 1
• Output Voltage: 4.4V
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: MSOP
• No. Of Pins: 10
• Operating Temperature Range: -40°C To +85°C
• 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

MOSFETs are very low, the TC654/TC655 can charge
and discharge them very quickly, leading to very fast
edges. Of key concern is the turn-off edge of the MOS-
FET. Since the fan motor winding is essentially an
inductor, once the MOSFET is turned off, the current
that was flowing through the motor wants to continue to
flow. If the fan does not have internal clamp diodes
around the windings of the motor, there is no path for
this current to flow through, and the voltage at the drain
of the MOSFET may rise until the drain to source rating
of the MOSFET is exceeded. This will most likely cause
FIGURE 7-7:
TABLE 7-2:
MMBT2222A
MPS2222A
MPS6602
SI2302
MGSF1N02E
SI4410
SI2308
Note 1: A series gate resistor may be used in order to control the MOSFET turn-on and turn-off times.
2002 Microchip Technology Inc.
Device
2: These drive devices are suggestions only. Fan currents listed are for individual fans.
FAN DRIVE DEVICE SELECTION TABLE (NOTE 2)
V
OUT
Package
Output Drive Device Configurations.
SOT-23
SOT-23
SOT-23
SOT-23
TO-92
TO-92
SO-8
R
BASE
a) Single Bipolar Transistor
Max Vbe sat /
Vgs(V)
1.2
1.2
1.2
2.5
2.5
4.5
4.5
GND
FAN
V
DD
R
Q
SENSE
1
Min hfe
NA
NA
NA
NA
50
50
50
the MOSFET to go into avalanche mode. Since there is
very little energy in this occurrence, it will probably not
fail the device, but it would be a long term reliability
issue. The following is recommended:
• Ask how the fan is designed. If the fan has clamp
diodes internally, you will not experience this
problem. If the fan does not have internal clamp
diodes, it is a good idea to put one externally
(Figure 7-8). You can also put a resistor between
V
slow down the turn-off and limit this condition.
V
OUT
OUT
and the gate of the MOSFET, which will help
Vce/V
40
20
20
30
60
40
40
DS
b) N-Channel MOSFET
TC654/TC655
FAN
GND
V
Fan Current
DD
R
Q
(mA)
SENSE
1000
1
150
150
500
500
500
500
DS21734A-page 25
Rbase (ohms)
Suggested
Note 1
Note 1
Note 1
Note 1
800
800
301