FUNCTIONAL DESCRIPTION
INTRODUCTION
FUNCTIONAL DESCRIPTION
INTRODUCTION
The 33298 was conceived, specified, designed, and
developed for automotive applications. It is an eight output
low side power switch having 8-bit serial control. The 33298
incorporates SMARTMOS™ technology having effective 1.5µ
CMOS logic, bipolar/MOS analog circuitry, and independent
state of the art double diffused MOS (DMOS) power output
transistors. Many benefits are realized as a direct result of
using this mixed technology. A simplified block diagram
delineates 33298 in
Where bipolar devices require considerable control
current for their operation, structured MOS devices, since
they are voltage controlled, require only transient gate
charging current affording a significant decrease in power
consumption. The CMOS capability of the SMARTMOS
process allows significant amounts of logic to be
economically incorporated into the monolithic design.
Additionally, the bipolar/MOS analog circuits embedded
within the updrain power DMOS output transistors monitor
and provide fast, independent protection control functions for
each individual output. All outputs have internal 65V at 0.5A
independent output voltage clamps to provide fast inductive
turn-off and transient protection.
The 33298 uses high efficiency updrain power DMOS
output transistors exhibiting very low room temperature
drain-to-source ON resistance values (R
DS(on)
≤
1.0Ω at 13V
V
PWR
) and dense CMOS control logic. Operational bias
currents of less than 2.0mA (1.0mA typical) with any
combination of outputs ON are the result of using this mixed
technology and would not be possible with bipolar structures.
To accomplish a comparable functional feature set using a
bipolar structure approach, would result in a device requiring
hundreds of milliamperes of internal bias and control current.
This would represent a very large amount of power to be
consumed by the device itself and not available for load use.
During operation, the 33298 functions as an eight output
serial switch serving as a microcontroller (MCU) bus
expander and buffer, with fault management and fault
reporting features.
In doing so, the device directly relieves the MCU of the
fault management functions.
The 33298 directly relieves the MCU of the fault
management functions. The 33298 directly interfaces to an
MCU, operating at system clock serial frequencies in excess
of 3.0MHz. It uses a Synchronous Peripheral Interface (SPI)
for control and diagnostic readout.
illustrates the
basic SPI configuration between an MCU and one 33298.
MC68HCXX
Microcontroller
MOSI
Shift Register
33298
SI
SO
Shift Register
MISO
Receive
Buffer
Parallel
Ports
SCLK
To
Logic
RST
CS
Figure 13. SPI Interface with Microcontroller
The circuit can also be used in a variety of other
applications in the computer, telecommunications, and
industrial fields. It is parametrically specified over an input
battery /supply range of 9.0 to 16V but is designed to operate
over a considerably wider range of 5.5 to 26.5V. The design
incorporates the use of Logic Level MOSFETs as output
devices. These MOSFETs are sufficiently turned ON with a
gate voltage of less than 5.0V thus eliminating the need for
an internal charge pump. Each output is identically sized and
independent in operation. The efficiency of each output
transistor, at room temperature provides as little as 9.0V
supply (V
PWR
), the maximum R
DS(on)
of an output
All inputs are compatible with 5.0V CMOS logic levels,
incorporating negative or inverted logic. Whenever an input is
programmed to a logic low state (<1.0V) the corresponding
low side switched output being controlled will be active low
and turned ON. Conversely, whenever an input is
programmed to a logic high state (>3.0V), the output being
controlled will be high and turned OFF.
33298
Analog Integrated Circuit Device Data
Freescale Semiconductor
13
FREESCALE [ FREESCALE SEMICONDUCTOR, INC ]
