L6727 STMicroelectronics, L6727 Datasheet - Page 14

• Manufacturer Part Number: L6727
• Description: IC PWM CTLR SGL PHASE SO-8
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6727

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adj to 0.8V
• Frequency - Switching: 300kHz
• Voltage - Input: 1.5 ~ 12 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Output Current: 1.5 A
• Input Voltage: - 0.3 V to + 15 V
• Switching Frequency: 300 KHz
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Duty Cycle (max): 80 %
• For Use With: 497-8266 - BOARD EVAL BASED ON L6727497-6258 - BOARD EVAL 1PH STPDWN CONV L6727
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Output voltage monitor and protections
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8.1
8.2
8.3
8.4
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Output voltage monitor and protections
L6727 monitors the voltage at FB pin and compares it to internal reference voltage in order
to provide Under Voltage and Over Voltage protections.
Undervoltage protection
If the voltage at FB pin drops below UV threshold (0.6 V typ), the device turns off both HS
and LS MOSFETs, waits for 2048 clock cycles and then performs a new soft start. If under
voltage condition is not removed, the device enters a hiccup mode with a typical period of
13.6 ms.
UVP is active from the end of soft start.
Overvoltage protection
If the voltage at FB pin rises over OV threshold (1 V typ), over voltage protection turns off HS
MOSFET and turns on LS MOSFET overriding PWM logic as long as over voltage is
detected.
OVP is always active with top priority as soon as over current threshold setting phase has
been completed.
Feedback disconnection protection
In order to provide load protection even if FB pin is not connected, a 100 nA bias current is
always sourced from this pin. If FB pin is not connected, this current will permanently pull up
FB over OVP threshold: thus LS will be latched on preventing output voltage from rising out
of control.
Undervoltage lock out
In order to avoid anomalous behaviors of the device when the supply voltage is too low to
support its internal rails, UVLO is provided: the device will start up when VCC reaches
UVLO upper threshold and will shutdown when VCC drops below UVLO lower threshold.
The 4.1 V maximum UVLO upper threshold allows L6727 to be supplied from 5 V and 12 V
busses in or-ing diode configuration.
Doc ID 12933 Rev 4
L6727