L6728A STMicroelectronics, L6728A Datasheet - Page 13

• Manufacturer Part Number: L6728A
• Description: Voltage Mode PWM Controllers Hi-Freq. singl-phase PWM controller w/Po
• Manufacturer: STMicroelectronics

Specifications of L6728A

• Number Of Outputs: Dual Output
• 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
• Package / Case: VFDFPN-10 EP
• Synchronous Pin: No
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

L6728A
8
Output voltage setting and protections
L6728A is capable to precisely regulate an output voltage as low as 0.8 V. In fact, the device
comes with a fixed 0.8 V internal reference that guarantee the output regulated voltage to be
within ±1% tolerance over line and temperature variations (excluding output resistor divider
tolerance, when present).
Output voltage higher than 0.8 V can be easily achieved by adding a resistor R
FB pin and ground. Referring to
where V
L6728A monitors the voltage at VSEN pin and compares it to internal reference voltage in
order to provide under voltage and overvoltage protections as well as PGOOD signal.
According to the level of VSEN, different actions are performed from the controller:
●
●
●
●
PGOOD
If the voltage monitored through VSEN exits from the PGOOD window limits, the device
de-asserts the PGOOD signal still continuing switching and regulating. PGOOD is
asserted at the end of the soft-start phase.
Under voltage protection
If the voltage at VSEN pin drops below UV threshold, the device turns off both HS and
LS MOSFETs, latching the condition. Cycle V
Overvoltage protection
If the voltage at VSEN pin rises over OV threshold (1 V typ), overvoltage protection
turns off HS MOSFET and turns on LS MOSFET. The LS MOSFET will be turned off as
soon as VSEN goes below V
recover. Notice that, even if the device is latched, the device still controls the LS
MOSFET and can switch it on whenever VSEN rises above 0.4V.
Feedback disconnection protection
In order to provide load protection even if VSEN pin is not connected, a 100 nA bias
current is always sourced from this pin. If VSEN pin is not connected, this current will
permanently pull it up causing the device to detect an OV: thus LS will be latched on
preventing output voltage from rising out of control.
REF
is 0.8 V.
V
OUT
Figure
REF
/2 (0.4 V). The condition is latched, cycle V
=
1, the steady state DC output voltage will be:
V
REF
⋅
⎛
⎝
Output voltage setting and protections
1
CC
+
to recover.
---------- -
R
R
OS
FB
⎞
⎠
OS
CC
between
to
13/32