MC33981BPNA Freescale, MC33981BPNA Datasheet - Page 27

• Manufacturer Part Number: MC33981BPNA
• Manufacturer: Freescale

Specifications of MC33981BPNA

• Switch Type: High Side
• Power Switch Family: MC33981B
• Power Switch On Resistance: 6mOhm
• Output Current: 40A
• Number Of Outputs: Single
• Mounting: Surface Mount
• Supply Current: 10mA
• Package Type: Power QFN
• Operating Temperature (min): -40C
• Operating Temperature Classification: Automotive
• Pin Count: 16
• Lead Free Status / RoHS Status: Compliant

APPLICATION
targeted automotive applications for the 33981. Conventional
solutions are designed with discrete components that are not
optimized in terms of component board size, protection, and
diagnostics. The 33981 is the right candidate to develop
lighter and more compact units.
of energy consumption. It is realized by chopping the supply
voltage, hence the mean voltage, applied to the motor. The
commonly used control technique is pulse wide modulation
(PWM) where the average voltage is proportional to the duty
cycle. Most applications require a PWM frequency of at least
20 kHz to avoid audible noise.
waveforms when switching the 33981 at 20 kHz with a duty
cycle of 80%. The output voltage (OUT) and current in the
motor (I
Analog Integrated Circuit Device Data
Freescale Semiconductor
Figure 33
Engine cooling, air conditioning, and fuel pump are the
The adjustment of the DC motor speed allows optimizing
MOTOR
Figure 34. Current and Voltage waveforms
Figure 33. Typical Application Diagram
illustrates the typical application diagram.
) waveforms are represented.
MC33981 ON
Imotor (10A/div)
Figure 34
MC33981 OFF
illustrates typical
OUT
POWER DISSIPATION
losses:
assumes that the current is constant in the load.
and the hypothesis is that the current is constant in the load.
ON-STATE LOSSES
calculated as follows:
increases with temperature. The 33981 has a maximum
R
is only 1.7 as shown in
SWITCHING LOSSES
as follows:
Pswitching = (t
where t
provides adjustable slew rates through an external capacitor
(SR) that slow down the rise and fall times to reduce the
electromagnetic emissions. However, this adjustment will
have an impact on power dissipation.
positive (SR
values of SR. This is illustrated in
Pon_state = a · R
DS(ON)
The 33981 power dissipation is the sum of two kinds of
• On-State losses when device is fully ON,
• Switching losses when the device switches ON and
The analysis that follows assumes an inductive load and
The case being considered in this paper is inductive load
The mean on-state loss periods in the 33981 can be
The critical parameter is the on resistance (R
The mean switching losses in the 33981 can be calculated
The switching time is a critical parameter. The 33981
7
6
5
4
3
2
1
0
OFF.
-50
ON
at 25ºC of 4.0 mΩ and its deviation with temperature
/t
OFF
Figure 35. R
R
) and negative (SR
V
ON
PWR
is the turn on/off time.
0
. F
DS(ON)
. I
REQ
OUT
Figure
DS(ON)
Temperature (°C)
. V
· I
) / 2
50
OUT
PWR
35.
2
vs. Temperature
F
where ‘a’ is the duty cycle.
. I
) slew rate versus different
Figure
OUT
100
TYPICAL APPLICATIONS
Figure 36
) / 2 + (t
POWER DISSIPATION
37.
150
OFF
DS(ON)
gives the
. F
REQ
) that
33981
200
.
27