MC33879APEK Freescale Semiconductor, MC33879APEK Datasheet - Page 15

• Manufacturer Part Number: MC33879APEK
• Description: CONFIG OCTAL SERIAL SW
• Manufacturer: Freescale Semiconductor

source is connected to ground. All outputs may be configured
individually as desired. When high side drive is used, the
33879 will limit the negative inductive transient to negative
20 V.
INTRODUCTION
switch with 16-bit serial control. A simplified internal block
diagram of the 33879 is shown in
DMOS output transistors exhibiting low drain-to-source ON
resistance (R
CMOS control logic. All outputs have independent voltage
clamps to provide fast inductive turn-off and transient
protection.
switch serving as a 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. This device directly interfaces to an MCU using a
SPI for control and diagnostic readout.
the basic SPI configuration between an MCU and one 33879.
levels and incorporate positive logic. When a SPI bit is
programmed to a logic [0], the corresponding output will be
OFF. Conversely, when a SPI bit is programmed to logic [1]
the output being controlled will be ON. Diagnostics are
treated in a similar manner. Outputs with a fault will feed back
(via DO) a logic [1] to the microcontroller, while normal
operating outputs will provide a logic [0].
the 33879. Data from the MCU is clocked daisy chain through
Analog Integrated Circuit Device Data
Freescale Semiconductor
The 33879 is an 8-output hardware-configurable power
The 33879 device uses high-efficiency up-drain power
In operation, the 33879 functions as an 8-output serial
All inputs are compatible with 5.0 V and 3.3 V CMOS logic
Figure 16
Microcontroller
Figure 15. SPI Interface with Microcontroller
Shift Register
MC68HCxx
Receive
Parallel
16 Bits
Buffer
Ports
illustrates the daisy chain configuration using
DS(ON)
= 0.75 Ω at 25°C typical) and dense
MISO
MOSI
SCLK
CS
Figure 2
DO
DI
Figure 15
on page 3.
Shift Register
MCU INTERFACE DESCRIPTION
33879
16 Bits
Logic
To
illustrates
EXPOSED PAD PIN
terminated (floating) however, it is recommended that the
Exposed Pad be terminated to pin 1 (GND) and system
ground.
each device while the
During each clock cycle, output status from the daisy chain is
transferred to the MCU via the Master In Slave Out (MISO)
line. On rising edge of
register is then transferred to the output driver.
fashion using the SPI.
24 loads using three dedicated parallel MCU ports for chip
select.
Microcontroller
SPI Interface
Device will perform as specified with the Exposed Pad un-
MC68HCxx
Multiple 33879 devices can be controlled in a parallel input
Microcontroller
SPI Interface
MC68HCxx
with
Parallel
Ports
with
Figure 16. 33879 SPI System Daisy Chain
Figure 17. Parallel Input SPI Control
C
A
B
MISO
MOSI
SCLK
Parallel Port
MOSI
SCLK
MISO
DO
CS
8 Outputs
CS
CS,
Figure 17
33879
bit is commanded low by the MCU.
command data stored in the input
DI
MCU INTERFACE DESCRIPTION
FUNCTIONAL DESCRIPTION
illustrates the control of
CS
DO
8 Outputs
33879
SCLK
SCLK
DO
SCLK
DO
DI
CS
SCLK
DO
DI
CS
DI
CS
DI
33879
33879
33879
DO
CS
8 Outputs
33879
8 Outputs
8 Outputs
8 Outputs
SCLK
33879
DI
15