MC33999 Datasheet, PDF (15/21 Pages) Motorola, Inc – 16-Output Switch with SPI and PWM Control

FUNCTIONAL DEVICE OPERATION
LOGIC COMMANDS AND REGISTERS
LOGIC COMMANDS AND REGISTERS
INTRODUCTION
The 33999 provides flexible control of 16 low-side driver
outputs. The device allows PWM and ON /OFF control
through the use of several input command words. This
section describes the logic operation and command registers
of the 33999.
The 33999 message set consists of seven messages as
shown in Table 5. Bits 23 through 18 determine the specific
command and bits 15 through 0 determine how a specific
output will operate. The 33999 operates on the command
word on the rising edge of CS.
Note Upon Power-ON Reset all bits are defined as shown
in Table 5.
Table 5. SPI Control Commands
Commands
MSB
23 22 21 20 19 18 17
ON/OFF Control Register 0
0
0000
X
0 = off, 1 = on
Open Load Current
0
0
0001
X
Enable
0 = disable, 1 = enable
Global Shutdown / Retry
0
0
0 0 1 0 Thermal
Control
Bit 0
0 = shutdown, 1 = retry
SFPD Control
0
0
0011
X
1 = therm only, 0 = V_DS
PWM Enable
0
0
0100
X
0 = SPI only, 1 = PWM
AND/OR Control
0
0
0101
X
0 = PWM pin AND with
SPI
1 = PWM pin OR with SPI
Reset
0
0
0110
X
SO Response
Any Over- 0 0 0 0
0
0 = No Fault, 1 = Fault Fault voltage
Bits
LSB
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
X
0000000000000000
X
0000000000000000
Over- X X X X X X X X X X X X X X X X
voltage
0
X
1111111111111111
X
0000000000000000
X
0000000000000000
X
XXXXXXXXXXXXXXXX
0
OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ON /OFF CONTROL REGISTER
To program the 16 outputs of the 33999 ON or OFF, a 24-
bit serial stream of data is entered into the SI pin. The first 8
bits of the control word are used to identify the on / off
command and the remaining 16 bits are used to turn ON or
OFF the specific output driver.
OPEN LOAD CURRENT ENABLE CONTROL
REGISTER
The Open Load Enable Control register is provided to
enable or disable the 50 µA open load detect pulldown
current. This feature allows the device to be used in LED
applications. Power-ON Reset (POR) or the RST pin or the
RESET command disables the 50 µA pulldown current. No
open load fault will be reported with the pulldown current
disabled. For open load to be active, the user must program
the Open Load Current Enable Control register with logic [1].
GLOBAL SHUTDOWN/RETRY CONTROL
REGISTER
The Global Shutdown/Retry Control register allows the
user to select the global fault strategy for the outputs. The
Overvoltage control bit (bit 16) sets the operation of the
outputs when returning from overvoltage. Setting the
Overvoltage bit to logic [0] will force all outputs to remain OFF
when V_PWR returns to normal level. Setting the Overvoltage
bit to logic [1] will command outputs to resume their previous
state when V_PWR returns to normal level. Bit 17 is the global
thermal bit. When bit 17 is set to logic [0], all outputs will shut
down when thermal limit is reached and remain off even after
cooled. With bit 17 set to logic [1], all outputs will shut down
when thermal limit is reached and will retry when cooled.
SHORT FAULT PROTECT DISABLE (SFPD)
CONTROL REGISTER
All outputs contain a current limit and thermal shutdown
with programmable retry. The SFPD control bits are used for
fast shutdown of the output when an overcurrent condition is
detected but thermal shutdown has not been achieved.
The SFPD Control register allows selection of specific
outputs for incandescent lamp loads and specific outputs for
inductive loads. By programming the specific SFPD bit as
logic [1], output will rely on Overtemperature Shutdown only.
Programming the specific SFPD bit as logic [0] will shut down
the output after 100 µs to 450 µs during turn on into short
circuit. The decision for shutdown is based on output drain-
to-source voltage (V_DS ) > 2.7 V. This feature is designed to
provide protection to loads that experience more than
expected currents and require fast shutdown. The 33999 is
designed to operate in both modes with full device protection.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33999
15