33993 Datasheet, PDF (22/28 Pages) Freescale Semiconductor, Inc – Multiple Switch Detection Interface

TYPICAL APPLICATIONS
INTRODUCTION
VBAT
1.5 kΩ
SG0
V_PWR V_PWR
16
2.0
mA
mA
SG0
100 kΩ
SP0
4.0 V Ref
+
-
To SPI
Comparator
V_PWR V_PWR
16
2.0
mA
mA
SG0
4.0 V
+
-
To SPI
16
mA
Ref
Comparator
2.0 mA
AMUX
SG13
V_PWR V_PWR
16
2.0
mA
mA
SG13
4.0 V Ref
+
-
To SPI
Comparator
Figure 14. MOSFET or LED Driver Output
The sequence of commands (from Normal mode with
inputs tri-state) required to set up the device to drive a
MOSFET are as follows:
• wetting current timer enable command –Disable SPn
wetting current timer (refer to Table 8, page 14)
• metallic command –Set SPn to 16 mA or 2.0 mA gate
drive current (refer to Table 7, page 14)
• settings command –Set SPn as switch-to-battery (refer
to Table 5, page 13)
• tri-state command –Disable tri-state for SPn (refer to
Table 9, page 14)
After the tri-state command has been sent (tri-state
disable), the MOSFET gate will be pulled to ground. From this
point forward the MOSFET may be turned on and off by
sending the settings command :
• settings command –SPn as switch-to-ground
(MOSFET ON)
• settings command –SPn as switch-to-battery
(MOSFET OFF)
Monitoring of the MOSFET drain in the OFF state provides
open load detection. This is done by using an SGn input
comparator. With the SGn input in tri-state, the load will pull
up the SGn input to battery. With open load the SGn pin is
pulled down to ground through an external resistor. The open
load is indicated by a logic [1] in the SO data bit.
The analog command may be used to monitor the drain
voltage in the MOSFET ON state. By sourcing 2.0 mA of
current to the 1.5 kΩ resistor, the analog voltage on the SGn
pin will be approximately:
V_SGn = I_SGn x 1.5 kΩ + V_DS
As the voltage on the drain of the MOSFET increases, so
does the voltage on the SGn pin. With the SGn pin selected
as analog, the MCU may perform the A / D conversion.
Using this method for controlling unclamped inductive
loads is not recommended. Inductive flyback voltages greater
than V_PWR may damage the IC.
The SP0 – SP7 pins of this device may also be used to
send signals from one module to another. Operation is similar
to the gate control of a MOSFET.
For LED applications a resistor in series with the LED is
recommended but not required. The switch-to-ground inputs
are recommended for LED application. To drive the LED use
the following commands:
• wetting current timer enable command –Disable SGn
wetting current timer
• metallic command –Set SGn to 16 mA
From this point forward the LED may be turned on and off
using the tri-state command :
• tri-state command –Disable tri-state for SGn (LED ON)
• tri-state command –Enable tri-state for SGn (LED OFF)
These parameters are easily programmed via SPI
commands in Normal mode.
MULTIPLE 33993 DEVICES IN A MODULE SYSTEM
Connecting power to the 33993 and the MCU for Sleep
mode operation may be done in several ways. Table 20
shows several system configurations for power between the
MCU and the 33993 and their specific requirements for
functionality.
Table 20. Sleep Mode Power Supply
MCU
V_DD
5.0 V
33993
V_DD
Comments
5.0 V
All wake-up conditions apply. (Refer to Sleep Mode,
page 17.)
5.0 V
0 V SPI wake-up is not possible.
Sleep mode not possible. Current from CS pull up will
0V
5.0 V flow through MCU to V_DD that has been switched off.
Negative edge of CS will put 33993 in Normal mode.
0V
0 V SPI wake-up is not possible.
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, 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
33993
22
Analog Integrated Circuit Device Data
Freescale Semiconductor