33888 datasheet(21/40 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33888

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

The FS pin is driven to a logic [0] when a fault exists on any

of the outputs. FS provides real time monitoring of the

overvoltage fault. For the high-side outputs, FS provides real

time monitoring of the open load and overtemperature. For

the low-side outputs, the FS is latched to a logic [0] for open

load, overtemperature, and overcurrent faults. The latch is

cleared by toggling the state of the faulted output or by

bringing RST low.

OVERTEMPERATURE FAULT

The 33888 incorporates overtemperature detection and

shutdown circuitry into each individual output structure.

Overtemperature detection occurs when an output is in the

ON state. When an output is shut down due to an

overtemperature condition, no other output is affected. The

output experiencing the fault is shut down to protect itself

from damage. A fault bit is loaded into the status register if the

overtemperature condition is removed, and the fault bit is

cleared upon the rising edge of CS.

For the low-side outputs, the faulted output is latched OFF

during an overtemperature condition. If the temperature falls

below the recovery level, TLIM(HYS), then the output can be

turned back ON only after the output has first been

commanded OFF either through the SPI or the ILS,

depending on the logic configuration.

For the high-side output(s), an overtemperature condition

will result in the output(s) turning OFF until the temperature

falls below the TLIM(HYS). This cycle will continue indefinitely

until action is taken by the MCU to shut the output(s) OFF.

OVERVOLTAGE FAULT

The 33888 shuts down all outputs during an overvoltage

condition on the VPWR pin. The outputs remain in the OFF

state until the overvoltage condition is removed. Fault status

for all outputs is latched into the status register. Following an

overvoltage condition, the next write cycle sent by the SO pin

of the 33888 is logic [1] on OD11:OD0, indicating all outputs

have shut down. If the overvoltage condition is removed, the

status register can be cleared by a rising edge on CS.

OPEN LOAD FAULT

The 33888 incorporates open load detection circuitry on

every output. A high-side or low-side output open load fault is

detected and reported as a fault condition when the

corresponding output is disabled (OFF) if it was configured

for open load detection by setting the appropriate bit to

logic [0] (HS3:HS0) or logic [1] (LS11:LS4) in the OLFCR

The high-side open load fault is detected and latched into

the status register after the internal gate voltage is pulled low

enough to turn off the output. If the open load fault is removed

or if the faulted output is commanded ON, the status register

can be cleared by a rising edge on CS. Note that the device

default state will enable the high-side open load detection

and disable the low-side open load detection circuits,

respectively.

It is recommended to disable the open load detection

circuitry (OL bit sets to logic [1]) in case of a permanent open

load fault condition.

Figure 7. Low-Side Output OFF Open Load Detection

OVERCURRENT FAULT REQUIREMENTS: LOW-

SIDE OUTPUT

An overcurrent condition is defined as any current value

greater than ILIM (500 mA minimum value for LS5, LS7, LS9,

LS11, and 800 mA minimum value for LS4, LS6, LS8, LS10).

The status of the corresponding bit in the CLOCCR register

determines whether a specific output shuts down or

continues to operate in an analog current limited mode until

either the overcurrent condition is removed or the thermal

shutdown limit is reached (Figure 10, page 27). If the

overcurrent shutdown mode is disabled, the fault reporting is

disabled as well.

For the low-side output of interest, if a D11:D4 bit was set

to a logic [1] in the OLCR register, the overcurrent protection

shutdown circuitry will be enabled for that output. When a

low-side output is commanded ON either from the SPI or the

ILS pin, the drain of the low-side driver will be monitored for

a voltage greater than the fault detection threshold (3.0 V

typical). If the drain voltage exceeds this threshold, a timer

will start and the output will be turned off and a fault latched

in the status register after the timeout expires. The faulted

output can be retried only by commanding the output OFF

and back ON either through the SPI or the ILS pin, depending

on the logic configuration. If the fault is gone, the retried

output will return to normal operation and the status register

can be cleared on a rising edge of CS. If the fault remains, the

VTHRES

MOSFET

LOW = Logic 0

50 mA

VOFD(THRES)LS

2.0 V–4.0 V

–

33888

VPWR

OUT

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