33811 Datasheet, PDF (13/18 Pages) Freescale Semiconductor, Inc – Solenoid Monitor Integrated Circuit (IC)

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
POWER SUPPLY
The 33811 is designed to operate from 10.5V to 15.5V on
the VPWR pin. The VPWR pin supplies power to the internal
regulator which, in turn, supplies the analog circuit blocks.
The VDD Supply is used internally to supply the logic
circuitry. The V_SPI supply is used for setting the SPI
communication threshold levels by supplying power to the
SO driver and the SI and CS input buffers. This IC
architecture provides flexible microprocessor interfacing.
When the MCU raises the RESET pin to a logic 1, the 33811
enters the Reset Mode causing two events to occur:
1) The internal Solenoid SPI register bits are cleared to 0.
2) The SO output pin is tri-stated, and pulled high by a pull-
up resistor, causing all subsequent SPI Responses to contain
all bits set to logic (1).
When the RESET pin is brought low again, the SO pin will
be un-tri-stated and the SPI data will again reflect the data
contained in the SPI register and the Solenoid fault register.
NORMAL MODE
The Normal Mode of operation occurs when the following
conditions are met:
1) Device Junction Temperature is below 125°C.
2) V_PWR is >10.5V and < 15.5V
3) V_DD is > 4.75V and < 5.5V
4) A logic low (0) level is present on the RESET pin.
5) V_SPI is 3.3V or 5.0 Volts
The major function of the 33811 integrated circuit is
provide the Engine or Transmission Control MCU with
information about the status of up to five solenoids. When a
solenoid is activated and operates properly, a unique current
profile is produced. This current profile can be observed as a
voltage waveform across the solenoid’s low side driver
MOSFET. The Solenoid Monitor inputs (SOLM1-5) on the
33811 are connected to voltage waveform monitoring circuits
that are capable of discerning a properly opening and closing
solenoid from one that is malfunctioning. When the 33811
determines that an solenoid is malfunctioning, a fault bit is set
in the corresponding Solenoid SPI register. When the MCU
interrogates the 33811 via the SPI, the solenoid fault will be
annunciated by setting the appropriate SPI fault bit to a logic
one (1).
SERIAL OUTPUT (SO) RESPONSE
All fault reporting is accomplished through the SPI
interface. All logic [1]s received by the MCU from the SO pin
indicate individual solenoid faults or the IC being held in the
RESET mode. All logic [0]s received by the MCU from the SO
pin indicate no fault, or normal operating solenoids. All fault
bits are cleared on the positive edge of CS. SO bits 15, 14,
13, 12, and 11 represent the fault status of
solenoids 4,3,2,1,and 5 respectively.
RESET MODE
The RESET pin is used to place the 33811 into the Reset
Mode. Normally the RESET pin is held at logic 0 by the MCU.
SPI COMMUNICATION
The 33811 integrated circuit communicates to the MCU via
the SPI (Serial Peripheral Interface).
The SPI communication can be between one MCU and
one 33811, or it can be between one MCU and several 33811
ICs.
The MCU can send two different SPI messages to the
33811, one 8 bits in length and one 16 bits in length. The
33811 responds by sending back 8 bit or 16 bit messages.
When the MCU sends an 8 bit message to the 33811, the
33811 responds by sending only the 8 bit fault status. The
fault status contains 5 bits of solenoid status and 3 bits of
logic zeros. When the MCU sends a 16 bit interrogate
message, the 33811 responds by sending the 8 bit fault
status message followed by the last 8 previously sent bits.
The 33811 IC does not decode the SPI messages from the
MCU. It will always respond in the same way, regardless of
the contents of the 8 or 16 bits sent. Hence, no specific SPI
commands are defined, and response is limited to either
solenoid fault status alone, when an 8 bit message is sent, or
the solenoid fault status along with the last 8 bits received
when a 16 bit message is sent. The two SPI scenarios are
outlined in the following diagrams.
SPI COMMUNICATION SUMMARY
1) The SPI communications sequence starts out in step 1
above with the contents of the MCU SPI shift register
containing 8 bits of x x x x x x x x and 8 bits of y y y y y y y
y. The 33811 SPI register contains a previous 8 bit byte of p
p p p p p p p and the contents of the solenoid status register
of 0 0 0 S5 S1 S2 S3 S4 is transferred into the SPI register.
The condition shown is prior to the SPI transfer.
2) The MCU starts the transfer of data from it’s 16 bit SPI
register to the 33811’s SPI register by setting CS to a logic 0
and by issuing 16 SCLK pulses. At the end of the 16 SCLK
pulses, the MCU brings CS back high to a logic 1. When the
transfer is complete the MCU now contains the contents of
the 33811’s SPI register and the 33811 contains the contents
of the MCU’s SPI register.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33811
13