33996 datasheet(13/23 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33996

LOGIC COMMANDS AND REGISTERS

INTRODUCTION

LOGIC COMMANDS AND REGISTERS

INTRODUCTION

The 33996 provides flexible control of 16 low-side driver

outputs. The device allows PWM and ON/OFF control

through the use of several 24-bit input command words. This

section describes the logic operation and command registers

of the 33996.

The 33996 message set consists of seven messages as

shown in Table 6. Bits 23 through18 determine the specific

command and bits 15 through 0 determine how a specific

output will operate. The 33996 operates on the command

word on the rising edge of CS.

Note Upon Power-ON Reset all bits are defined as shown

in Table 6.

ON/OFF CONTROL REGISTER

To program the 16 outputs of the 33996 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

The Open Load Current Enable Control register is

provided to enable or disable the 50

µA open load detect pull-

down 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 pull-down current.

No open load fault will be reported with the pull-down 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

The Global Shutdown/Retry Control register allows the

user to select the global fault strategy for the outputs. The

over-voltage control bit (bit 16) sets the operation of the

outputs when returning from over-voltage. Setting the over-

voltage bit to logic [0] will force all outputs to remain off when

VPWR returns to normal level. Setting the over-voltage bit to

logic [1] will command outputs to resume their previous state

when VPWR 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 current limit and thermal shutdown with

programmable retry. The SFPD control bits are used for fast

shutdown of the output when overcurrent condition is

detected but thermal shutdown has not been achieved.

The SFPD Control register allows the user to select

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 over temperature

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

Table 6. SPI Control Commands

MSB

Bits

LSB

Commands

ON/OFF Control

0=off, 1=on

Open Load Current Enable

0=disable, 1=enable

Global Shutdown/Retry

Control

0=shutdown, 1=retry

Thermal

Bit 0

Over-

voltage

SFPD Control

1=therm only, 0=VDS

PWM Enable

0=SPI only, 1=PWM

AND/OR Control

0=PWM pin AND with SPI

1=PWM pin OR with SPI

Reset

SO Response

0=No Fault, 1=Fault

Any

Fault

over-

volt-

age

OUT

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