TLD5541-1QV Datasheet, PDF (23/82 Pages) Infineon Technologies AG – H-Bridge DC/DC Controller with SPI Interface

H-Bridge DC/DC Controller with SPI Interface
TLD5541-1QV
Regulator Description
6.2
Adjustable Soft Start Ramp
The soft start behavior limits the current through the inductor and the external MOSFET switches during
initialization (at first turn on and restarting after output fault condition).
The soft start function gradually increases the current of the inductor (L_OUT) over t_{SOFT_START} to minimize potential
overvoltage at the output. The soft start ramp is defined by a capacitor placed at the SOFT_START pin.
Selection of the SOFT_START capacitor (C_{SOFT_START}) can be done according to the approximate formula
described in Equation (1):
t_{SOFT_ START}
=
Vss_th_ eff
I
⋅ C_{SOFT_ START}
(1)
SOFT _ START(PU)
Note: V_{ss_th_eff} is the soft start effectiveness threshold, that depends on load condition. Its value is about 0.7V for
the buck mode and 1.4V for the boost mode
The SOFT START pin is also used to define a fault filter time.
Once an open load or a short on the output is detected, a pull-down current source I_{SOFT_START_PD} (P_6.4.20) is
activated. This current brings down the V_{SOFT_START} until V_{SOFT_START_RESET} (P_6.4.22) is reached, then the pull-up
current source I_{SOFT_START_PU} (P_6.4.19) turns on again. If the fault condition hasn’t been removed until
V_{SOFT_START_LOFF} (P_6.4.21) is reached, the pull-down current source turns back on again, initiating a new cycle.
This will continue until the fault is removed.
6.3
Switching Frequency setup
The switching frequency can be set from 200 kHz to 700 kHz by an external resistor connected from the FREQ
pin to GND or by suppliyng a sync signal as specified in chapter Chapter 11.2. Select the switching frequency with
an external resistor according to the graph in Figure 7 or the following approximate formulas.
f_SW [kHz] = 5375 * R_FREQ [kΩ]^-0.8
(2)
R_FREQ[kΩ] = 46023* f_SW[kHz]^−1.25
(3)
Figure 7 Switching Frequency f_SW versus Frequency Select Resistor to GND R_FREQ
6.4
Operation of 4 switches H-Bridge architecture
Inductor L_OUT connects in an H-Bridge configuration with 4 external N channel MOSFETs (M1, M2, M3 & M4)
Data Sheet
23
Rev. 1.0, 2016-05-20