l9958 STMicroelectronics, l9958 Datasheet - Page 18

• Manufacturer Part Number: l9958
• Description: Low Rdson Spi Controlled H-bridge
• Manufacturer: STMicroelectronics

Current regulation
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selection can be done "on the fly" by SPI. The corresponding bits are called "VSR" and
"ISR". No external component is needed to select the slew rate range. Only the power
transistors not used for freewheeling can be adjusted, the two others can be controlled with
a preset slew rate.
The couples of value defined to fulfill most of the application requirements are described in
the table below. The required accuracy is ±50 % for an output current from 1A to 8A and with
output voltage up to 19 V. The overall delay implemented between high-side and low-side
transistor switching must be adjusted automatically to avoid any cross-conduction through
one half-bridge in all conditions.
Table 10.
In case of current limitation and any detection that put the bridge in tri-state, the slew rate is
not related anymore to the preset bits "VSR"; "ISR" but to a dedicated faster slew rate
control named "SUPER FAST" mode. The automatic change from SPI selectable to SUPER
FAST slew rate is described hereafter.
Figure 14. Slew rate switching strategy
CURRENT_LIM
1 (default value)
No SR control
SLEW RATE
(*) NSR: Normal Slew Rate
BLANKING
SFSR: Super-Fast Slew Rate
Range
PWM
Once I > IH,
we start blanking
and in SFSR
2
3
4
Slew rate control on low side MOS
I
LS
IH
IL
0
NSR
t
off-min
(*)
Note: Current limitation state is reached when I > IL the end of blanking (MOS is switched-OFF by the device, user looses control).
time is started at each HS switched-OFF while in SFRS mode
This information is latched in ILIM SPI bit. When toff-min is started due to PWM falling edge in SFSR, the ILIM SPI bit is not
set (MOS is switched-OFF by user).
PWM control remains active during blanking (user can switch-off).
VSR
t
Not selectable
0
0
1
1
b
Doc ID 17269 Rev 1
(end of blanking OR PWM falling edge)
t
Ignored
(t
off-min
off_min
ISR
)
0
1
0
1
t
b
t
off-min
SFSR
Once I < IL,
and after t
L9958 leaves
current limitation
dV/dt (V/µs)
(*)
14
4
4
2
2
off-min
t
off-min
When (I < IL)
and (after t
and i_pwm = '0',
L9958 go back to NSR
(otherwise L9958 remains
in SFSR mode)
off-min
dI/dt (A/µs)
)
0.3
0.3
14
3
3
NSR
(*)
AC00664
L9958
t