10XSD200 Datasheet, PDF (38/60 Pages) Freescale Semiconductor, Inc – Dual 10 mOhm High Side Switch

FUNCTIONAL DEVICE OPERATION
OPERATION AND OPERATING MODES
FAULTR register is read during the ON state, provided the
failure cause (load disconnected) has disappeared.
In low current mode (CSR1), OL_ON is done periodically
instead of continuously, and only operates when fast slew
rate is selected. When the internal PWM module is used with
an internal or external clock (case 1), the period is 150 ms
(typ.). When the direct inputs are used (case 2), the period is
that of the input signal. The detection instants in both cases
are given by the following:
1. In internal PWM (int./ext. clock), low current mode
(CSR1), OpenLoad in ON state detection is not
performed each switching period, but at a fixed
frequency of about 7.0 Hz (each t_OLLED =150 ms typ.).
The function is available for a duty cycle of 100%.
OLON detection is also performed at 7.0 Hz, at the first
turn-off event occurring 150 ms after the previous
OL_ON detection event (before OS and OL_OFF).
2. In direct input, low current mode (CSR1), OL_ON is
performed each switching period (at the turn-off
instant) but the duty cycle is restricted to the values.
Consequently, when the signal on the IN[x] pin has a
duty cycle of 100%, OL_ON is not performed. To solve
this problem, either the internal PWM function must be
activated with a duty cycle of 100%, or the channel’s
direct input must be disabled by setting Dir_dis_s=1
(bit D5 of the CONFR-s register). The OLON-bit is only
reset when the FAULTR register is read after
occurrence of an OL_ON detection event without fault
presence.
OpenLoad Detection in Discontinuous Conduction Mode
If small inductive loads (solenoids / DC motors) are driven
at low frequencies, discontinuous conduction mode may
occur. Undesired OpenLoad in On state errors may then be
detected, as the inductor current needs some time to rise
above the OpenLoad detection threshold after turn-on. This
problem can be solved by increasing the switching
frequency, or by disabling the function and activating
OpenLoad in Off state detection instead.
When small DC motors are driven in discontinuous
conduction mode, undesired OpenLoad in Off state detection
may also occur when the load current reaches 0 A during the
Off state. This problem can be solved by increasing the
switching frequency, or by enabling OpenLoad in the Off
state detection only during a limited time, preferably directly
after turn-off (see Diagnostic Features). The signal on the
SYNC pin can be used to identify the turn-off instant.
CURRENT & TEMPERATURE SENSING
The scaled values of either of the output currents or the
temperature of the device’s GND pin (#14) can be made
available at the CSNS pin. To monitor the current of a
particular channel or the general device temperature, the
CSNS0_en and CSNS1_en bits (see Table 22) in the general
configuration register (GCR) must be set to the appropriate
values. When overcurrent windows are active, current
sensing is disabled and the SYNCB pin remains high.
10XSD200
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Instantaneous and Sampled Current Sensing
The device offers two possibilities for load current sensing:
instantaneous (synchronous) sensing mode and track & hold
mode (see Figure 9). In synchronous mode, the load current
is mirrored through the current sense pin (Output Current
Monitoring (CSNS)) and is therefore synchronous with it.
After turn-off, the current sense pin does not output the
channel current. In track & hold mode however, the current
sense pin continues to mirror the load current as it was just
before turn-off. Synchronous mode is activated by setting the
T_H_en bit to 0, and Track & Hold mode by setting the
T_H_en bit to 1.
Current Sense Ratio Selection
The load current is mirrored through the CSNS pin with a
sense ratio (Figure 17) selected by the CSNS_ratio bit in the
OCR register. To achieve optimal accuracy at low current
levels, the lower current sensing ratio, called CSR1, can be
selected. In that case, the overcurrent threshold levels are
decreased. The best accuracy that can be obtained for both
ratios is shown in Figure 18. The amount of current the CSNS
pin can sink is limited to I_CSNS,MAX..The CSNS pin must be
connected to a pull-down resistor (470  < R(CSNS) <10 k,
1.0 k typical), in order to generate a voltage output. A small
low-pass filter can be used for filtering out switching
transients (Figure 21). Current sensing operates for load
currents up to the lower overcurrent threshold (OCLx A).
Synchronous Current Sensing Mode
For activation of synchronous mode, T_H_en must be set
to 0 (default). After turn-on, the CSNS output current
accurately reflects the value of the channel’s load current
after the required settling time. From this moment on (CSNS
valid), the SYNC pin goes low and remain low until a switch
off signal (internal/external) is received. This allows
synchronization of the device’s current sensing feature with
an external process running on a separate device (see
Current Sense Synchronization (SYNC)). After turn-off, the
load current does not flow through the switch, and the load
current cannot be monitored.
Track & Hold Current Sensing Mode
In Track & Hold mode (T&H) (T_H_en = 1), conversely
from synchronous mode, the CSNS output current is
available even after having switched off the load. This feature
is useful when the device operates autonomously (internal
clock/PWM), since it allows current monitoring without any
synchronization of the device. An external sample and hold
(S/H) capacitor is not required. After turn on, the CSNS
output current reflects the channel’s load current with the
specified accuracy, after occurrence of the negative edge on
the SYNC pin, as in synchronous mode (see Current Sense
Synchronization (SYNC)). However, at the switch-off instant,
the last observed CSNS current is sampled and its value
saved, thanks to an internal S/H capacitor. The SYNC pin
goes high (SYNC = 1). If the channel on which Track & Hold
current sensing is performed is changed to another, the
Analog Integrated Circuit Device Data
Freescale Semiconductor