MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33298
13
SYSTEM/APPLICATION INFORMATION
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 1.5 μ
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 Figure 1.
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 45 V at 0.5 A 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)
≤
1.0
at 13 V V
PWR
)
and dense CMOS control logic. Operational bias currents of
less than 2.0 mA (1.0 mA 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 3.0 MHz. It uses
a Synchronous Peripheral Interface (SPI) for control and
diagnostic readout. Figure 11 illustrates the basic SPI
configuration between an MCU and one 33298.
Figure 11. 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 16 V but is designed to operate over a considerably wider
range of 5.5 to 26.5 V. 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 5.0 V 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 9.0 V supply (V
PWR
), the maximum R
DS(on)
of an output
All inputs are compatible with 5.0 V CMOS logic levels,
incorporating negative or inverted logic. Whenever an input is
programmed to a logic low state (<1.0 V) 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 (>3.0 V), the output being controlled will be high
and turned OFF.
33298
MC68HCXX
Microcontroller
Shift Register
Shift Register
To
Logic
Receive
Buffer
Parallel
Ports
MOSI
SI
MISO
SO
SCLK
RST
CS
F
Freescale Semiconductor, Inc.
Go to: www.freescale.com
n
.