FUNCTIONAL DESCRIPTION
INTRODUCTION
FUNCTIONAL DESCRIPTION
INTRODUCTION
The 33874 is one in a family of devices designed for low-
voltage automotive and industrial lighting and motor control
applications. Its four low RDS(ON) MOSFETs (35mΩ) can
control the high sides of four separate resistive or inductive
loads.
allows the user to program via the SPI the fault current trip
levels and duration of acceptable lamp inrush or motor stall
intervals. Such programmability allows tight control of fault
currents and can protect wiring harnesses and circuit boards
as well as loads.
The 33874 is packaged in a power-enhanced 12 x 12
nonleaded PQFN package with exposed tabs.
Programming, control, and diagnostics are accomplished
using a 16-bit SPI interface. Additionally, each output has its
own parallel input for PWM control if desired. The 33874
FUNCTIONAL PIN DESCRIPTION
when transitioning from logic [0] to logic [1]. This pin should
not be allowed to be logic [1] until VDD is in regulation. This
OUTPUT CURRENT MONITORING (CSNS)
The Current Sense pin sources a current proportional to
the designated HS0:HS3 output. That current is fed into a
ground-referenced resistor and its voltage is monitored by an
MCU's A/D. The output to be monitored is selected via the
SPI. This pin can be tri-stated through the SPI.
pin has a passive internal pull-down.
CHIP SELECT (CS)
The CS pin enables communication with the master
microcontroller (MCU). When this pin is in a logic [0] state,
the device is capable of transferring information to, and
receiving information from, the MCU. The 33874 latches in
data from the Input Shift registers to the addressed registers
on the rising edge of CS. The device transfers status
information from the power output to the Shift register on the
falling edge of CS. The SO output driver is enabled when CS
is logic [0]. CS should transition from a logic [1] to a logic [0]
state only when SCLK is a logic [0]. CS has an active internal
SERIAL INPUTS (IN0, IN1, IN2, IN3)
The IN0:IN3 high side input pins are used to directly
control HS0:HS3 high side output pins, respectively. A SPI
register determines if each input is activated or if the input
logic state is ORed or ANDed with the SPI instruction. These
pins are to be driven with 5.0V CMOS levels, and they have
an active internal pull-down current source.
pull-up, IUP
.
TEMPERATURE FEEDBACK (TEMP)
This pin reports an analog voltage value proportional to the
temperature of the GND. It is used by the MCU to monitor
board temperature.
SERIAL CLOCK (SCLK)
The SCLK pin clocks the internal shift registers of the
33874 device. The serial input (SI) pin accepts data into the
input shift register on the falling edge of the SCLK signal
while the serial output (SO) pin shifts data information out of
the SO line driver on the rising edge of the SCLK signal. It is
important the SCLK pin be in a logic low state whenever CS
makes any transition. For this reason, it is recommended the
SCLK pin be in a logic [0] whenever the device is not
accessed (CS logic [1] state). SCLK has an active internal
pull-down. When CS is logic [1], signals at the SCLK and SI
pins are ignored and SO is tri-stated (high-impedance) (see
Figure 9, page 18).
FAULT STATUS (FS)
This pin is an open drain configured output requiring an
external pull-up resistor to VDD for fault reporting. If a device
fault condition is detected, this pin is active LOW. Specific
device diagnostic faults are reported via the SPI SO pin.
WAKE
This input pin controls the device mode and watchdog
timeout feature if enabled. An internal clamp protects this pin
from high damaging voltages when the output is current
limited with an external resistor. This input has a passive
internal pull-down.
SERIAL INPUT (SI)
This is a serial interface (SI) command data input pin.
Each SI bit is read on the falling edge of SCLK. A 16-bit
stream of serial data is required on the SI pin, starting with
D15 to D0. The internal registers of the 33874 are configured
and controlled using a 5-bit addressing scheme described in
Table 8, page 22. Register addressing and configuration are
RESET (RST)
This input pin is used to initialize the device configuration
and fault registers, as well as place the device in a low-
current sleep mode. The pin also starts the watchdog timer
33874
Analog Integrated Circuit Device Data
Freescale Semiconductor
15
FREESCALE [ Freescale ]
