TC646 Microchip, TC646 Datasheet - Page 15

• Manufacturer Part Number: TC646
• Description: PWM Fan Speed Controller
• Manufacturer: Microchip

FIGURE 5-8:
TABLE 5-2:
5.6
As with any CMOS IC, the potential exists for latch-up
if signals are applied to the device which are outside
the power supply range. This is of particular concern
during power-up if the external circuitry (such as the
sensor network, V
powered by a supply different from that of the TC646.
Care should be taken to ensure that the TC646’s V
supply powers up first. If possible, the networks
attached to V
ply at the same physical location as the IC itself. Even
if the IC and any external networks are powered by the
same supply, physical separation of the connecting
points can result in enough parasitic capacitance and/
or inductance in the power supply connections to delay
one power supply “routing” versus another.
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
Latch-up Considerations
NOTE: *Value depends on the specific application and is shown for example only.
IN
and V
TRANSISTORS AND MOSFETS FOR Q
AS
Package
SOT-23
SOT-23
SOT-23
SOT-23
TO-92
TO-92
AS
SO-8
Power the Fan from a -12V Supply.
divider or shutdown circuit) is
should connect to the V
TC646
Max. V
+5V
GND
V
DD
BE(sat)
(V)
1.2
1.2
1.2
2.5
2.5
4.5
4.5
V
DD
OUT
/V
sup-
GS
DD
Min. H
12.0V
Zener
D
NA
NA
NA
NA
50
50
50
1
5.7
Noise present on the V
erroneous operation of the FAULT output. As a result,
these inputs should be bypassed with a 0.01 µF
capacitor mounted as close to the package as possible.
This is especially true of V
from a high impedance source (such as a thermistor).
In addition, the V
1 µF capacitor. Grounds should be kept as short as
possible. To keep fan noise off the TC646 ground pin,
individual ground returns for the TC646 and the low
side of the fan current sense resistor should be used.
FE
1
(V
R
2.2 k
2
*
DD
V
CEO
= 5V)
(V)
Power Supply Routing and
Bypassing
40
40
40
20
20
30
60
/V
R
10 k
DS
4
*
DD
Fan Current
input should be bypassed with a
(mA)
1000
150
150
500
500
500
500
IN
-12V
and V
Fan
IN
Q
, which is usually driven
R
2.2
1
*
3
AS
*
inputs may cause
DS21446C-page 15
TC646
Suggested
R
BASE
Note 1
Note 1
Note 1
Note 1
800
800
301
( )