MC33288 데이터 시트보기 (PDF) - Motorola => Freescale
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MC33288 Datasheet PDF : 8 Pages
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Freescale Semiconductor, Inc.
MC33288
Introduction
DEVICE DESCRIPTION
device incorporates a current limitation at 30 Amps typical.
The MC33288DH is a dual high side switch with This mean that the really first inrush current will be clamped at
appropriate control, protection, and diagnostic features 30 Amps. The second lamp turn on of the flashing cycle will
dedicated to automotive flasher applications. The device not see any clamping as the lamps have been heated up in the
consists of two independent 25mΩ power switches and an previous cycle.
additionnal 3.2 Ohm high side switch capable of controlling a
In-1 and In-2 are the two inputs of the device, connected to
1.2W warning lamp. It interfaces directly with a microcontroller a microcontroller I/O ; they are CMOS compatible. When
and the package used is a HSOP20 power small outline, 20 these inputs are in low state, the device is in standby mode.
pins. The MC33288 incorporates a status pin and a load When any of the inputs are switched to a high level, the
current sense capability.
associated output MOSFET is turned on.
Power Supply
The MC33288 can be directly connected to the supply
line. In standby mode (In-1 & In-2 @ OV), the supply current is
less than 10µA for Vbat supply voltage below 14V. This
feature allows a very low supply current on the battery when
the car is idle or parked.
During off state, the current recopy pin and the status pins
are in high impedance.
In case of loss of (digital) ground, the power MOSFETs
turn off in order to safely tie the load current to zero.
Nominal Voltage and Transient Operation
The nominal operation voltage is from 9 to 16V. The
MC33288 is functional over a larger voltage range from 8V to
35V. The technology used for both power and analog circuitry
sustains 40V DC voltage.
Reverse Battery
The MC33288 is self protected against reverse battery up
to -14 Volts in a continuous mode. When a negative battery
voltage arises, the MOSFETS are internally turned off. The
load current flows in the body diode of each MOSFET. The
power dissipation within the MC33288DH is then Vf x Iload,
where Iload is the total current set by the loads and Vf is the
forward body diode voltage. Vf is 0.5V typical at 150°C and
decreases with temperature with a drop of -2mV/°C.
Power Output Switches
The device has two independent high side switches. Each
switch is realised with an N-channel power MOSFET and
includes current and temperature sensing circuitries. The
MOSFET gates are driven by analog circuitry which includes
charge pump and fault detection. A specific feature of this
device is the output current recopy.
Each output has a 25mΩ Rdson max at 25°C. The Rdson
value reaches 40mΩ at 150°C junction temperature. Each
output has a parasitic drain to source diode, inherent to the
technology. This diode can sustain as much current as the
MOSFET. This diode is reversed biased during normal
operation of the MOSFET and is forward biased during
reverse battery or negative transient pulses.
The output MOSFET can each drive 8 Amps nominal. This
maximum current condition occurs when up to three 21W
lamps and two small 5 or 7W lamps are connected on each
channel, at higher Vbat voltage specification. This is the case
when a trailor is attached to the car. As the flasher can operate
in warning or hazard operation mode with its two channels on,
the MC33288 can drive 16 Amps total.
When lamps are turned on, the inrush current can reach
up to 6 times the nominal lamp current. For this particular
application, the total inrush current can reach 6 time 8 Amps,
that is up to 48Amps per channel. The 48Amps value will only
occur at the first lamp turn on. In order to optimise the total
system,(MC33288, printed circuit board, wiring, fuse etc.) the
Status
The device has a single status pins which reports an over
temperature and an openload condition in the device. This pin
is an open drain structure and needs an external pull up
resistor. The device incorporates overtemperature sense on
each output MOSFET in order to independently protect each
output. But , the report of the overtemperature is done through
one single status pin called Status, in order to minimise the
number of I/O connection of the MCU.
Open Load Function
The open load detection is active during the ON phase (Hot
open load detection). An amplifier measures the differential volt-
age between Vbat and Vout .
When the load current is below 1A, the open load circuitry will
pull down the status output. If the open load condition is present
before the device turn-on, the status will be pulled down after a
delay due to the rise time of the output.
Current Recopy Function
Flasher application needs to detect failed lamp. The
system must detect one 21W lamp failing, in the flasher
application only, without a trailor. The MC33288 has an output
current recopy function which recopies on the Cur R pin a
portion of the output current. Each channel is connected to the
same Cur R pin as the system have to operate in the flasher
mode only and not in the warning operation.
The MC33288 provides a current recopy of 1/1000 of the
main output current, either output left or right. The recopy
function has its higher accuracy of +-10% in the usual
operation range and an accuracy of +-20% in the total
operating range. This allows a precise detection of one 21W
lamp, but also the detection of additional lamps in case of
trailor connection.
An external resistor must be connected to the Cur R pin
and then tied to a microcontroller A/D input for analog voltage
measurement. The Cur R pin is internally clamped to protect
the MCU A/D input.
Warning Lamp Driver
The warning lamp driver is a 3.2 Ohms Rdson max High
Side MOSFET to control the 1.2W dashboard warning lamp.
This output is current limited and thermally protectedactivated
only in the warning mode. It is turned on by activation of both
right and left inputs (IN1 and IN2)
Package
The device is assembled into a power surface mount
package. This package offers high thermal performances and
high current capabilities. It offers 10 pins on each package
sides and an additional pin which is the package heat sink ,
called pin 21. The heak sink acts as the MC33288 power Vbat
connection.
For More Information On This Product,
Go to: www.freescale.com
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