L6728HTR STMicroelectronics, L6728HTR Datasheet - Page 11
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L6728HTR
Manufacturer Part Number
L6728HTR
Description
IC CTLR PWM SGL PHASE 10-DFN
Manufacturer
STMicroelectronics
Datasheet
1.L6728HTR.pdf
(32 pages)
Specifications of L6728HTR
Pwm Type
Voltage Mode
Number Of Outputs
1
Frequency - Max
330kHz
Duty Cycle
80%
Voltage - Supply
4.5 V ~ 12 V
Buck
Yes
Boost
No
Flyback
No
Inverting
No
Doubler
No
Divider
No
Cuk
No
Isolated
No
Operating Temperature
-40°C ~ 125°C
Package / Case
10-DFN
Frequency-max
330kHz
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
497-8978-2
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
L6728H
7
7.1
Soft-start
L6728H implements a soft-start to smoothly charge the output filter avoiding high in-rush
currents to be required from the input power supply. The device gradually increases the
internal reference from 0 V to 0.8 V in 4.5 ms (typ.), in closed loop regulation, linearly
charging the output capacitors to the final regulation voltage.
In the event of an over current triggering during soft start, the over current logic will override
the soft start sequence and will shut down the PWM logic and both the high side and low
side gates. This condition is latched, cycle VCC to recover.
The device begins soft start phase only when VCC power supply is above UVLO threshold
and over current threshold setting phase has been completed.
Low-side-less startup (LSLess)
In order to avoid any kind of negative undershoot and dangerous return from the load during
start-up, L6728H performs a special sequence in enabling LS driver to switch: during the
soft-start phase, the LS driver results disabled (LS = OFF) until the HS starts to switch. This
avoid the dangerous negative spike on the output voltage that can happen if starting over a
pre-biased output.
If the output voltage is pre-biased to a voltage higher than the final one, the HS would never
start to switch. In this case, at the end of soft start time, LS is enabled and discharge the
output to the final regulation value.
This particular feature of the device masks the LS turn-on only from the control loop point of
view: protections by-pass this turning ON the LS MOSFET in case of need.
Figure 4.
LSLess startup (left) vs non-LSLess startup (right)
Doc ID 15725 Rev 1
Soft-start
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