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L9953

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L9953 / L9953XP Application information
Doc ID 14278 Rev 4 19/38
3 Application information
3.1 Dual power supply: V
S
and V
CC
The power supply voltage V
S
supplies the half bridges and the highside drivers. An internal
charge-pump is used to drive the highside switches. The logic supply voltage V
CC
(stabilized
5 V) is used for the logic part and the SPI of the device.
Due to the independent logic supply voltage the control and status information will not be
lost, if there are temporary spikes or glitches on the power supply voltage. In case of power-
on (V
CC
increases from under voltage to V
POR OFF
= 4.2 V) the circuit is initialized by an
internally generated power-on-reset (POR). If the voltage V
CC
decreases under the
minimum threshold (V
POR ON
= 3.4 V), the outputs are switched to tristate (high impedance)
and the status registers are cleared.
3.2 Standby mode
The standby mode of the L9953 is activated by clearing the bit 23 of the Input Data Register
0. All latched data will be cleared and the inputs and outputs are switched to high
impedance. In the standby mode the current at V
S
(V
CC
) is less than 6 µA (50µA) for
CSN = high (DO in tristate). By switching the V
CC
voltage a very low quiescent current can
be achieved. If bit 23 is set, the device will be switched to active mode.
3.3 Inductive loads
Each half bridge is built by an internally connected highside and a lowside power DMOS
transistor. Due to the built-in reverse diodes of the output transistors, inductive loads can be
driven at the outputs OUT1 to OUT5 without external free-wheeling diodes. The highside
drivers OUT6 to OUT8 are intended to drive resistive loads. Hence only a limited energy
(E<1mJ) can be dissipated by the internal ESD-diodes in freewheeling condition. For
inductive loads (L>100μH) an external free-wheeling diode connected to GND and the
corresponding output is needed.
3.4 Diagnostic functions
All diagnostic functions (over/open load, power supply over-/under voltage, temperature
warning and thermal shutdown) are internally filtered and the condition has to be valid for at
least 32 µs (open load: 1ms, respectively) before the corresponding status bit in the status
registers will be set. The filters are used to improve the noise immunity of the device. Open
load and temperature warning function are intended for information purpose and will not
change the state of the output drivers. On contrary, the overload condition will disable the
corresponding driver (over-current) and over temperature will switch off all drivers (thermal
shutdown). Without setting the over-current recovery bits in the Input Data register, the
microcontroller has to clear the over-current status bits to reactivate the corresponding
drivers.
Application information L9953 / L9953XP
20/38 Doc ID 14278 Rev 4
3.5 Overvoltage and under voltage detection
If the power supply voltage V
S
rises above the overvoltage threshold V
SOV OFF
(typical 21
V), the outputs OUT1 to OUT8 are switched to high impedance state to protect the load.
When the voltage V
S
drops below the under voltage threshold V
SUV OFF
(UV-switch-OFF
voltage), the output stages are switched to the high impedance to avoid the operation of the
power devices without sufficient gate driving voltage (increased power dissipation). If the
supply voltage V
S
recovers to normal operating voltage the outputs stages return to the
programmed state (input register 0: bit 20=0).
If the under voltage/overvoltage recovery disable bit is set, the automatic turn-on of the
drivers is deactivated. The microcontroller needs to clear the status bits to reactivate the
drivers. It is recommended to set bit 20 to avoid a possible high current oscillation in case of
a shorted output to GND and low battery voltage.
3.6 Charge pump
The charge pump runs under all conditions in normal mode. In standby the charge pump is
disabled.
3.7 Temperature warning and thermal shutdown
If junction temperature rises above T
j TW
a temperature warning flag is set and is detectable
via the SPI. If junction temperature increases above the second threshold T
j SD
, the thermal
shutdown bit will be set and power DMOS transistors of all output stages are switched off to
protect the device. Temperature warning flag and thermal shutdown bit are latched and must
be cleared by the microcontroller. The related bit is only cleared if the temperature
decreases below the trigger temperature. If the thermal shutdown bit has been cleared the
output stages are reactivated.
3.8 Open load detection
The open load detection monitors the load current in each activated output stage. If the load
current is below the open load detection threshold for at least 1 ms (t
dOL
) the corresponding
open load bit is set in the status register. Due to mechanical/electrical inertia of typical loads
a short activation of the outputs (e.g. 3ms) can be used to test the open load status without
changing the mechanical/electrical state of the loads.
3.9 Over load detection
In case of an over-current condition a flag is set in the status register in the same way as
open load detection. If the over-current signal is valid for at least t
ISC
= 32 µs, the over-
current flag is set and the corresponding driver is switched off to reduce the power
dissipation and to protect the integrated circuit. If the over-current recovery bit of the output
is zero the microcontroller has to clear the status bits to reactivate the corresponding driver.
L9953 / L9953XP Application information
Doc ID 14278 Rev 4 21/38
3.10 Current monitor
The current monitor output sources a current image at the current monitor output which has
a fixed ratio (1/10000) of the instantaneous current of the selected highside driver. The bits
18 and 19 of the Input Data Register 0 control which of the outputs OUT1, OUT4, OUT5,
and OUT8 will be multiplexed to the current monitor output. The current monitor output
allows a more precise analysis of the actual state of the load rather than the detection of an
open- or overload condition. For example this can be used to detect the motor state
(starting, free-running, stalled). Moreover, it is possible to regulate the power of the defroster
more precise by measuring the load current. The current monitor output is bidirectional (c.f.
PWM inputs).
3.11 PWM inputs
Each driver has a corresponding PWM enable bit which can be programmed by the SPI
interface. If the PWM enable bit in Input Data Register 1 is set, the output is controlled by the
logically AND-combination of the PWM signal and the output control bit in Input Data
Register 0. The outputs OUT1-OUT6 and OUT8 are controlled by the PWM1 input and the
output OUT7 is controlled by the bidirectional input CM/PMW2. For example, the two PWM
inputs can be used to dim two lamps independently by external PWM signals.
3.12 Cross-current protection
The six half-bridges of the device are cross-current protected by an internal delay time. If
one driver (LS or HS) is turned-off the activation of the other driver of the same half bridge
will be automatically delayed by the cross-current protection time. After the cross-current
protection time is expired the slew-rate limited switch-off phase of the driver will be changed
to a fast turn-off phase and the opposite driver is turned-on with slew-rate limitation. Due to
this behavior it is always guaranteed that the previously activated driver is totally turned-off
before the opposite driver will start to conduct.
3.13 Programmable softstart function to drive loads with higher
inrush current
Loads with start-up currents higher than the over-current limits (e.g. inrush current of lamps,
start current of motors and cold resistance of heaters) can be driven by using the
programmable softstart function (i.e. overcurrent recovery mode). Each driver has a
corresponding over-current recovery bit. If this bit is set, the device will automatically switch-
on the outputs again after a programmable recovery time. The duty cycle in over-current
condition can be programmed by the SPI interface to be about 12% or 25%. The PWM
modulated current will provide sufficient average current to power up the load (e.g. heat up
the bulb) until the load reaches operating condition. The PWM frequency settles at 3kHz or
6kHz. The device itself cannot distinguish between a real overload and a non linear load like
a light bulb. A real overload condition can only be qualified by time. As an example the
microcontroller can switch on light bulbs by setting the over-current Recovery bit for the first
50ms. After clearing the recovery bit the output will be automatically disabled if the overload
condition still exits.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P38

L9953

Mfr. #:
Buy L9953
Manufacturer:
STMicroelectronics
Description:
IC DVR DOOR ACTUATOR POWERSO-36
Lifecycle:
New from this manufacturer.
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