mc33198dr2 Freescale Semiconductor, Inc, mc33198dr2 Datasheet - Page 12

• Manufacturer Part Number: mc33198dr2
• Description: Automotive High-side Tmos Driver
• Manufacturer: Freescale Semiconductor, Inc

to allow inrush current.
SOURCE (PIN1) AND DRAIN (PIN2)
FUNCTIONALITY
conditions. Pin 2 is connected to the internal pull down
current source of 80mA and to the C2 comparator. An
external resistor connected between pin 2 and VBAT creates
a voltage drop across this resistor. The voltage drop will be
the MOSFET maximum acceptable drain to source voltage
and the C2 comparator threshold.
different cases should be considered, MOSFET on or off :
conditions, the V
developed at pin 2. So, the C2 comparator output is low and
the status is high. No current will flow through the pin 8
capacitor.
shorted to Gnd, the voltage at the source will cross the pin 2
voltage and go below this pin 2 voltage, thereby turning on
the C2 comparator. The comparator will pull the status pin 6
low and will enable the charge of the pin 8 capacitor. When
the voltage at the capacitor reaches 5.5V, the C3 comparator
will switch off the MOSFET by disabling the charge pump and
the 110mA current source. The MOSFET gate will be
discharged only by the 10mA current source. The MOSFET
is latched off and can be turned back on again by switching
the input pin 7 to 0 and back to 1.
Under normal conditions, the load should pull the source
voltage to Gnd, thus C2 comparator output is high and status
pin pulled low. If the load is shorted to VBAT for instance,
source pin will be higher than pin 2, The C2 output
comparator is low and the status pin is high. This is
summarized in
Table 5. Status Functionality
12
33198
FUNCTIONAL DESCRIPTION
INTRODUCTION
INPUT
PIN 7
In addition, the pin 8 capacitor value should be calculated
These two pins are used to sense the MOSFET and load
Pin 1 is connected to the MOSFET source pin. Two
When the MOSFET is on and working under normal
If the MOSFET encounters an overload or if the load is
When the MOSFET is off, we have the same scheme.
High
High
Low
Low
Short to GND
CONDITION
Short Circuit
or Overload
Normal
to V
Normal
Table 5, Status
BAT
DS
should be less than the voltage
VOLTAGE
SOURCE
<V
>V
>V
<V
LOAD
PIN2
PIN2
PIN2
PIN2
Functionality.
OUTPUT
COMP
High
High
Low
Low
C2
STATUS
PIN 6
High
High
Low
Low
Charge by
Charge by
TIMER
source
source
10 µA
10 µA
PIN 8
Low
Low
OPERATION WITH INDUCTIVE LOADS
switching applications. In this case, a 1.0kW resistor should
be connected between source of the MOSFET and device pin
1. The resistor will limit the current flowing into pin 1 and
prevent MC33198 from damage while switching the inductive
load off. The gate voltage is internally clamped at - Vbe (0.6V
typical), and the V
prevent excessive power dissipation in the MOSFET. The
load voltage is limited to V
reasonable discharge current.
SWITCHING ON
charge pump. The charge pump response time versus the
MOSFET gate capacitance is shown in
Electrical
SWITCHING OFF
normally switching off, and the switching off under a fault
condition. The normal switching off is done by internal pull
down current sources. The value is 110mA and is in fact
composed of two current sources in parallel: a 100mA and a
10mA source. The 10mA current is always connected to the
gate pin 4 as shown in the
the MOSFET is switched off under fault conditions. The
device will disable the 100mA current source and the
MOSFET gate will be discharged only by a 10mA current.
The time required to switch off the MOSFET will be much
longer in this case, and will result in a lower overvoltage at the
MOSFET, especially when the device drives high inductive
loads.
OFF STATE OPERATION WITHOUT VCC
CONNECTION
is present, the gate voltage is discharged by the 110mA
current source. In the case of a V
sustaining 5.0mA pull down current source is incorporated in
the device, to ensure that the MOSFET gate capacitor is
discharged and tied below 0.9V. In case of a VCC
disconnection, input pin 7 has no effect on the gate voltage,
which is maintained below 0.9V. In this case, the status pin is
high. Low leakage current at pin 2 (10mA max) allows the
operation with the MOSFET and MC33198 pin 2 permanently
connected to the battery. V
switched off from the main battery line. See
PWM OPERATION
current, the MOSFET gate can be charged fast enough to
allow for PWM operations. The maximum PWM frequency is
dependent on the MOSFET itself and mainly its gate to the
source capacitor value. Depending on the PWM frequency,
The device can drive the MOSFET during inductive loads
The MOSFET switching on is ensured by the internal
Here two cases have to be discussed: the MOSFET
The 100mA source can be disabled. This is the case when
When pin 7 is in the low state, the MOSFET is off. If V
Since the MC33198 charge pump can deliver a high
Characteristics.
DS
is limited to V
Analog Integrated Circuit Device Data
BE
Internal Block Diagram on page
CC
+ V
and other functions can be
GSON
BAT
BAT
Freescale Semiconductor
disconnection, a self
and allows a
+ V
Table 4, Dynamic
BE
Figure
+ V
GSON
18.
to
BAT
2.