MC33993DWB Freescale Semiconductor, MC33993DWB Datasheet - Page 20

• Manufacturer Part Number: MC33993DWB
• Description: IC SWITCH I/O INTERFACE 32-SOIC
• Manufacturer: Freescale Semiconductor

Specifications of MC33993DWB

• Applications: *
• Interface: *
• Voltage - Supply: *
• Package / Case: 32-SOIC (7.5mm Width)
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

closed switch contacts. However, there are many features
that allow the device to be used in a variety of applications.
The following is a list of applications to consider for the IC:
detail.
SENSOR POWER SUPPLY
external to a module. Many sensors such as Hall effect,
pressure sensors, and temperature sensors require a supply
voltage to power the sensor and provide an open collector or
analog output.
to supply power and interface to these types of sensors. In an
application where the input makes continuous transitions,
consider using the wake-up / interrupt command to disable
the interrupt for the particular input.
20
33993
TYPICAL APPLICATIONS
INTRODUCTION
Reg
X
The 33993’s primary function is the detection of open or
• Sensor Power Supply
• Switch Monitor for Metallic or Elastomeric Switches
• Analog Sensor Inputs (Ratiometric)
• Power MOSFET / LED Driver and Monitor
• Multiple 33993 Devices in a Module System
The following paragraphs describe the applications in
Each input may be used to supply current to sensors
Hall-Effect
Sensor
VBAT
VBAT
16 mA
SG12
SG13
SP7
SG0
SG1
SP0
SP1
Figure 12. Sensor Power Supply
Figure 12
16
mA
16
mA
V
V
PWR
PWR
V
V
33993
PWR
PWR
shows how the 33993 may be used
2.5 kΩ
2.0
mA
2.0
mA
WAKE
SCLK
V
V
PWR
INT
2.5 kΩ
SO
CS
DD
SI
V
DD
TYPICAL APPLICATIONS
MOSI
SCLK
CS
MISO
INT
IOC[7:0]
Input Capture
Timer Port
MCU
INTRODUCTION
METALLIC / ELASTOMERIC SWITCH
resistance over time owing to contact corrosion. The
corrosion is induced by humidity, salt, and other elements
that exist in the environment. For this reason the 33993
provides two settings for contacts. When programmed for
metallic switches, the device provides higher wetting current
to keep switch contacts free of oxides. The higher current
occurs for the first 20 ms of switch closure. Where longer
duration of wetting current is desired, the user may send the
wetting current timer command and disable the timer. Wetting
current will be continuous to the closed switch. After the time
period set by the MCU, the wetting current timer command
may be sent again to enable the timer. The user must
consider power dissipation on the device when disabling the
timer. (Refer to the paragraph entitled
page 18.)
contact, the user has two options. Higher wetting current to a
switch may be achieved by paralleling SGn or SPn inputs.
This will increase wetting current by 16 mA for each input
added to the switch contact. The second option is to simply
add an external resistor pull-up to the V
to-ground inputs or a resistor to ground for a switch-to-battery
input. Adding an external resistor has no effect on the
operation of the device.
a high contact resistance. Resistance of 1.0 kΩ is common.
In applications with elastomeric switches, the pull-up and
pull-down currents must be reduced to prevent excessive
power dissipation at the contact. Programming for a lower
current settings is provided in the
Operation
Metallic Command.
ANALOG SENSOR INPUTS (RATIOMETRIC)
the binary code for a specific input in the analog command
allows the microcontroller to perform analog to digital
conversion on any of the 22 inputs. On rising edge of CS the
multiplexer connects a requested input to the AMUX pin. The
AMUX pin is clamped to max of V
higher voltages present on the input pin. After an input has
been selected as the analog, the corresponding bit in the next
SO data stream will be logic [0].
configured as analog with high impedance, analog with
2.0 mA pull-up, or analog with 16 mA pull-up.
page 21, shows how the 33993 may be used to provide a
ratiometric reading of variable resistive input.
Metallic switch contacts often develop higher contact
To increase the amount of wetting current for a switch
Elastomeric switch contacts are made of carbon and have
The 33993 features a 22-to-1 analog multiplexer. Setting
The input pin, when selected as analog, may be
Section beginning on page
Analog Integrated Circuit Device Data
Functional Device
DD
Freescale Semiconductor
volts regardless of the
11
Temperature
PWR
under
supply for switch-
Figure
Table
Monitor,
13,
7,