TC642COA Microchip Technology, TC642COA Datasheet - Page 6

• Manufacturer Part Number: TC642COA
• Description: IC PWM FAN SPEED CONTRLR 8-SOIC
• Manufacturer: Microchip Technology
• Type: Controller - PWM Fanr

Specifications of TC642COA

• Package / Case: 8-SOIC (3.9mm Width)
• Operating Temperature: 0°C ~ 70°C
• Applications: Fan Controller, Brushless (BLDC)
• Number Of Outputs: 1
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Product: Fan / Motor Controllers / Drivers
• Operating Supply Voltage: 6 V
• Supply Current: 1 mA
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Load: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

TC642
The second condition by which the TC642 detects a
fault is when the PWM control voltage applied to V
becomes greater than that needed to drive 100% duty
cycle (see Section 1.0, “Electrical Characteristics”).
This indicates that the fan is at maximum drive and the
potential exists for system overheating. Either heat dis-
sipation in the system has gone beyond the cooling
system’s design limits or some subtle fault exists (such
as fan bearing failure or an airflow obstruction). This
output may be treated as a system overheat warning
and be used to trigger system shutdown. However, in
this case, the fan will continue to run even when FAULT
is asserted. If a shutdown is
connected to V
TC642 in shutdown mode when any fault occurs.
3.3
The V
or MOSFET as the low side power switching element
in the system. Various examples of driver circuits will
be shown throughout this data sheet. This output has
asymmetric complementary drive and is optimized for
driving NPN transistors or N-channel MOSFETs. Since
the system relies on PWM rather than linear control,
the power dissipation in the power switch is kept to a
minimum. Generally, very small devices (TO-92 or
SOT packages) will suffice.
3.4
To ensure reliable fan start-up, the Start-up Timer turns
the V
the fan is started from the off state. This occurs at
power-up and when coming out of shutdown mode. If
the PWM frequency is 30 Hz (C
start-up time will be approximately one second. If a
fault is detected, the Diagnostic Timer is triggered
once, followed by the Start-up Timer. If the fault per-
sists, the device is shut down (see Section 3.2, “FAULT
Output”).
DS21444C-page 6
OUT
OUT
V
Start-Up Timer
output on for 32 cycles of the PWM whenever
pin is designed to drive a low cost transistor
OUT
MIN
Output
outside the device. This will latch the
desired,
F
= 1 µF), the resulting
FAULT may be
IN
3.5
If V
into shutdown mode. This can be accomplished by
driving V
an external transistor, as shown in Figure 3-1. All func-
tions are suspended until the voltage on V
higher than V
below V
shutdown
unconditionally inactive in shutdown mode.
A small amount of hysteresis, typically one percent of
V
and V
and V
include this hysteresis, plus adequate margin to
account for normal variations in the absolute value of
the threshold and hysteresis.
3.6
The SENSE input (Pin 5) is connected to a low value
current sensing resistor in the ground return leg of the
fan circuit. During normal fan operation, commutation
occurs as each pole of the fan is energized. This
causes brief interruptions in the fan current, seen as
pulses across the sense resistor. If the device is not in
shutdown mode, and pulses are not appearing at the
SENSE input, a fault exists.
The short, rapid change in fan current (high dI/dt)
causes a corresponding dV/dt across the sense
resistor, R
tiated and converted to a logic-level pulse-train by
C
The presence and frequency of this pulse-train is a
direct indication of fan operation (see Section 5.0, “Typ-
ical Applications”, for more details).
CAUTION: Shutdown mode is unconditional. That is,
the fan will not be activated regardless of the voltage
at V
producing activity in the system is at a negligible level.
DD
SENSE
MIN
(50 mV at V
IN
REL
REL
. The fan should not be shut down until all heat
(Pin 3) is pulled below V
MIN
SHDN
Shutdown Control (Optional)
SENSE Input
(FanSense Technology)
and the internal signal processing circuitry.
SENSE
thresholds. The levels specified for V
in Section 1.0, “Electrical Characteristics”,
and
with an open-drain logic signal or by using
REL
will always result in complete device
. The waveform on R
DD
(0.85V @ V
reset.
= 5.0V), is designed into the V
2002 Microchip Technology Inc.
The
DD
SHDN
= 5.0V). Pulling V
FAULT
, the TC642 will go
SENSE
MIN
output
is differen-
becomes
SHDN
SHDN
MIN
is