L6728ATR STMicroelectronics, L6728ATR Datasheet - Page 11
L6728ATR
Manufacturer Part Number
L6728ATR
Description
IC CTLR PWM SGL HI FREQ 10VFQFPN
Manufacturer
STMicroelectronics
Datasheet
1.L6728ATR.pdf
(32 pages)
Specifications of L6728ATR
Pwm Type
Voltage Mode
Number Of Outputs
1
Frequency - Max
660kHz
Duty Cycle
67%
Voltage - Supply
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
660kHz
Topology
Buck
Output Voltage
0.8 V
Output Current
1500 mA
Switching Frequency
660 KHz
Duty Cycle (max)
67 %
Maximum Operating Temperature
+ 125 C
Minimum Operating Temperature
- 40 C
Synchronous Pin
No
For Use With
497-8228 - BOARD EVALUATION W/L6728497-6418 - BOARD EVAL BASED ON L6728
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
497-8324-2
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
L6728A
6
6.1
Soft-start
L6728A 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 msec (typ.), in closed loop regulation, linearly
charging the output capacitors to the final regulation voltage. A pre-charged output voltage
will affect the soft-start duration, resulting in a reduction of this period of time (< 4 msec).
During the soft-start process all the protections but the UVP are active: the UVP becomes
active as soon as the soft-start ends up.
The device begins soft-start phase only when
and over-current threshold setting phase has been completed.
Low-side-less start up (LSLess)
In order to avoid any kind of negative undershoot and dangerous return from the load during
start-up, L6728A 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)
V
CC
power supply is above UVLO threshold
Soft-start
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