MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33888
25
Figure 6. Low-Side Output OFF Open Load Detection
Overcurrent Fault Requirements: Low-Side Output
An overcurrent condition is defined as any current value
greater than I
LIM
(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 7
, page 26). 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
terminal, 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 terminal, 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 retried output will
latch off after the fault timer expires and the fault bit will remain
set in the status register.
For the low-side output of interest, if a D11:D4 bit was set to
a logic [0] in the OLCR register, the output experiencing an
overcurrent condition is not disabled until an overtemperature
fault threshold has been reached. The specific output goes into
an analog current limit mode of operation, I
LIM
. The 33888 uses
overtemperature shutdown to protect all outputs in this mode of
operation. If the overcurrent condition is removed before the
output has reached its overtemperature limit, the output will
function as if no fault has occurred.
Note that each pair of low-side drivers, LS4:LS5, LS6:LS7,
LS8:LS9, and LS10:LS11, consists of a 500 mA and a 800 mA
output. Each pair of outputs shares ground bondwires. The
bondwires are not rated to handle both outputs in current limit
mode simultaneously.
Overcurrent Fault Requirements: High-Side Output
For the high-side output of interest, the output current is
limited to one of four levels depending on the type of high-side
output, the amount of time that has elapsed since the output
was switched on, and the state of the CLOCCR register.
Assuming that bits D3:D0 of the CLOCCR register are at
logic [0], the current limit levels of the outputs will be initially at
their peak levels as specified by the I
LIM(PK)HS[0:3]
. After the
high-side output is switched on, the peak current timer starts.
After a period of time t
PCT
, the current limit level changes to the
sustain levels I
LIMSUSHS[x,x]
.
For the high-side output of interest, if a D3:D0 bit of the
CLOCCR is at logic [1], then the assigned output will only
current limit at the sustain level specified by I
LIMSUSHS[x,x]
.
Current is limited until the overtemperature circuitry shuts
OFF the device. The device turns ON automatically when the
temperature fails below the T
LIM(HYS)
. This cycle continues
indefinitely until action is taken by the master to shut the
output(s) OFF.
Reverse Battery Requirements
The low-side and high-side outputs survive the application of
reverse battery as low as -16 V.
Ground Disconnect Protection
In the event that the 33888 ground is disconnected from load
ground, the device protects itself and safely turns OFF the
outputs, regardless of the state of the output at the time of
disconnection.
OUTPUT
V
THRES
MOSFET
R
L
V
PWR
LOW = Logic 0
50 mA
V
OFD(THRES)LS
2.0 V–4.0 V
–
+
33888
V
PWR
R
L
OUT
F
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
.