MC33198 Datasheet, PDF (9/11 Pages) Motorola, Inc – Automotive High Side TMOS Driver

MC33198
Freescale Semiconductor, Inc.
This resistor will reduce in some way the charge pump Reverse Battery
output voltage available for the MOSFET, but the device will
The device does not sustain reverse battery operation for
still provide enough Gate-to-Source voltage to maintain the Vcc voltage greater than - 0,6V in magnitude. In application,
MOSFET on in good conditions. The resistor will mainly act as pin 5 should be protected from reverse battery by connecting
an additional discharge current, which will reduce the
switching off time of the overall application. See the table 2
below and figure 11 which show the pin 4 voltage depending
a diode in series with the V_bat line.
Figure15.
on the additional gate resistor and the off switching time due
Vbat
to this resistor.
Vbat
If a very low switching time is needed, the resistor has to
be extremely low, resulting in low gate voltage not high
enough to ensure proper MOSFET operation. In this case, a
logic level MOSFET can be used. Logic level will operate with
5
VCC
DRN 2
R _drn
Vgs of 5V with the same performance as a standard MOSFET
having a 12V Vgs. Care should be taken regarding maximum
gate to source voltage of a logic level MOSFET. An additional
6 STATUS
GATE 4
zener might be necessary to prevent gate oxyde damages.
Table 2 •Switching Off Characteristics with
MOSFET Additional Gate Resistor
7 INPUT
1K
SOURCE 1
GND
3
TIMER
8
LOAD
C
Rgate
VCC (V)
Vgate (V)
Toff
No R
7
16
450
10
14
20
68 kΩ
7
10
14
23
700
Pin 2 which is normally connected to resistor, can sustain
reverse battery operation, providing that the DRN resistor is
28
750
higher than 3,3K. A 1K resistor at pin 1 is also necessary to
34
780
limit the reverse current flowing through the MOSFET body
diode.
14
160
Figure16. MC33198 Gnd Disconnection Circuitry
22
230
5V
Vbat
Vbat
27
230
20
33
220
39 kΩ
7
10
14
20
15 kΩ
7
10
14
20
13
100
5
21
160
4
6
26
160
Device drive
circuitry and
MC33198
32
150
interface
IN
7
1
LOAD
11
30
17,5
50
Module Gnd
8
3
C
24
50
28,5
50
Q1
R1
NOTE 1 : Time from negative edge of input signal (Pin 7) to negative edge
of gate voltage (Pin 4) measured at 5V threshold.
NOTE 2 : Gate discharge time, not LOAD switching OFF time.
NOTE 3 : TMOS used is Motorola MTP50N06, load 10Ω resistor.
Additional circuitry
to present MOSFET
turn-on in case of module
Gnd disconnection
R1 = 3,3K
Q1 = 2N2222
Operation
When module Gnd is disconnected and if VBAT
connection is still present, pin 3 of MC33198 goes to about 2/3
of V_bat if additional circuitry is not inserted.
With R1/Q1, Gate/Source voltage of MOSFET is shorted
as soon as pin 3 voltage rises above Gnd level.
For More Information On This Product,
MC33198
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