33982B Datasheet, PDF (15/34 Pages) Freescale Semiconductor, Inc – Single Intelligent High-Current Self-Protected Silicon High-Side Switch (2.0 mohm)

FUNCTIONAL DESCRIPTION
INTRODUCTION
FUNCTIONAL DESCRIPTION
INTRODUCTION
The 33982B is a self-protected silicon 2.0 mΩ high-side
switch used to replace electromechanical relays, fuses, and
discrete devices in power management applications. The
33982B is designed for harsh environments, including self-
recovery features. The device is suitable for loads with high
inrush current, as well as motors and all types of resistive and
inductive loads.
Programming, control, and diagnostics are implemented
via the Serial Peripheral Interface (SPI). A dedicated parallel
input is available for alternate and pulse width modulation
(PWM) control of the output. SPI programmable fault trip
thresholds allow the device to be adjusted for optimal
performance in the application.
The 33982B is packaged in a power-enhanced 12 x 12
nonleaded PQFN package with exposed tabs.
FUNCTIONAL PIN DESCRIPTION
OUTPUT CURRENT MONITORING (CSNS)
The CSNS pin outputs a current proportional to the high-
side output current and used externally to generate a ground-
referenced voltage for the microcontroller to monitor output
current.
WAKE (WAKE)
This pin is used to input a Logic [1] signal in order to enable
the watchdog timer function. 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 pulldown.
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 when
transitioning from logic LOW to logic HIGH. This pin should
not be allowed to be logic HIGH until V_DD is in regulation. This
pin has a passive internal pulldown.
DIRECT IN (IN)
The Input pin is used to directly control the output. This
input has an active internal pulldown current source and
requires CMOS logic levels. This input may be configured via
SPI.
FAULT STATUS (FS)
This is an open drain configured output requiring an
external pullup resistor to V_DD for fault reporting. When a
device fault condition is detected, this pin is active LOW.
Specific device diagnostic faults are reported via the SPI SO
pin.
FAIL-SAFE INPUT (FSI)
The value of the resistance connected between this pin
and ground determines the state of the output after a
watchdog time-out occurs. Depending on the resistance
value, either the output is OFF or ON. When the FSI pin is
connected to GND, the watchdog circuit and fail-safe
operation are disabled. This pin incorporates an active
internal pullup current source.
CHIP SELECT (CS)
This input pin is connected to a chip select output of a
master microcontroller (MCU). The MCU determines which
device is addressed (selected) to receive data by pulling the
CS pin of the selected device logic LOW, enabling SPI
communication with the device. Other unselected devices on
the serial link having their CS pins pulled up logic HIGH
disregard the SPI communication data sent. This pin
incorporates an active internal pullup current source.
SERIAL CLOCK (SCLK)
This input pin is connected to the MCU providing the
required bit shift clock for SPI communication. It transitions
one time per bit transferred at an operating frequency, f_SPI,
defined by the communication interface. The 50 percent duty
cycle CMOS-level serial clock signal is idle between
command transfers. The signal is used to shift data into and
out of the device. This input has an active internal pulldown
current source.
SERIAL INTERFACE (SI)
This is a command data input pin connected to the SPI
Serial Data Output of the MCU or to the SO pin of the
previous device in a daisy chain of devices. The input
requires CMOS logic level signals and incorporates an active
internal pulldown current source. Device control is facilitated
by the input's receiving the MSB first of a serial 8-bit control
command. The MCU ensures data is available upon the
falling edge of SCLK. The logic state of SI present upon the
rising edge of SCLK loads that bit command into the internal
command shift register.
DIGITAL DRAIN VOLTAGE POWER (VDD)
This is an external voltage input pin used to supply power
to the SPI circuit. In the event V_DD is lost, an internal supply
provides power to a portion of the logic, ensuring limited
functionality of the device. All device configuration registers
are reset.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33982
15