MC33993DWB Ver la hoja de datos (PDF) - Motorola => Freescale
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MC33993DWB Datasheet PDF : 28 Pages
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Multiple 33993 devices may be used in a module system.
SPI control may be done in parallel or serial. However when
parallel mode is used, each device is addressed independently
(refer to MCU Interface Description on page 11). Therefore
when sending the sleep command, one device will enter sleep
before the other. For multiple devices in a system, it is
recommended that the devices are controlled in serial (S0 from
first device is connected to SI of second device). With two
devices, 48 clock pulses are required to shift data in. When the
WAKE feature is used to enable the power supply, both WAKE
pins should be connected to the enable pin on the power
supply. The INT pins may be connected to one interrupt pin on
the MCU or may have their own dedicated interrupt to the MCU.
The transition from Normal to Sleep mode is done by
sending the sleep command. With the devices connected in
serial and the sleep command sent, both will enter Sleep mode
on the rising edge of CS. When Sleep mode is entered, the
WAKE pin will be logic [1]. If either device wakes up, the WAKE
pin will transition low, waking the other device.
A condition exists where the MCU is sending the sleep
command (CS logic [0]) and a switch input changes state. With
this event the device that detects this input will not transition to
Sleep mode, while the second device will enter Sleep mode. In
this case two switch status commands must be sent to receive
accurate switch status data. The first switch status command
will wake the device in Sleep mode. Switch status data may not
be valid from the first switch status command because of the
time required for the input voltage to rise above the 4.0 V input
comparator threshold. This time is dependant on the
impedance of SGn or SPn node. The second switch status
command will provide accurate switch status information. It is
recommended that software wait 10 ms to 20 ms between the
two switch status commands, allowing time for switch input
voltages to stabilize. With all switch states acknowledged by the
MCU, the sleep sequence may be initiated. All parameters for
Sleep mode should be updated prior to sending the sleep
command.
The 33993 IC has an internal 5.0 V supply from VPWR pin. A
POR circuit monitors the internal 5.0 V supply. In the event of
transients on the VPWR pin, an internal reset may occur. Upon
reset the 33993 will enter Normal mode with the internal
registers as defined in Table 10, page 17. Therefore it is
recommended that the MCU periodically update all registers
internal to the IC.
Using the WAKE Feature
The 33993 provides a WAKE output and wake-up input
designed to control an enable pin on system power supply.
While in the Normal mode, the WAKE output is low, enabling the
power supply. In the Sleep mode, the WAKE pin is high,
disabling the power supply. The WAKE pin has a passive pull-
up to the internal 5.0 V supply but may be pulled up through a
resistor to VPWR supply (see Figure 14, page 24)
When the WAKE output is not used the pin should be pulled
up to the VDD supply through a resistor as shown in Figure 13,
page 24.
During the Sleep mode, a switch closure will set the WAKE
pin low, causing the 33993 to enter the Normal mode. The
power supply will then be activated, supplying power to the VDD
pin and the microprocessor and the 33993. The microprocessor
can determine the source of the wake-up by reading the
interrupt flag.
Cost and Flexibility
Systems requiring a significant number of switch interfaces
have many discrete components. Discrete components on
standard PWB consume board space and must be checked for
solder joint integrity. An integrated approach reduces solder
joints, consumes less board space, and offers wider operating
voltage, analog interface capability, and greater interfacing
flexibility.
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33993/D
23
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