L4949ED STMicroelectronics, L4949ED Datasheet - Page 13

• Manufacturer Part Number: L4949ED
• Description: IC VREG VLDO MULTIFUNCT SO-8
• Manufacturer: STMicroelectronics

Specifications of L4949ED

• Regulator Topology: Positive Fixed
• Voltage - Output: 5V
• Voltage - Input: Up to 28V
• Voltage - Dropout (typical): 0.3V @ 100mA
• Number Of Regulators: 1
• Current - Output: 100mA
• Current - Limit (min): 120mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Number Of Outputs: 1
• Polarity: Positive
• Input Voltage Max: 28 V
• Output Voltage: 5 V
• Output Type: Fixed
• Dropout Voltage (max): 0.5 V
• Output Current: 100 mA
• Line Regulation: 20 mV
• Load Regulation: 30 mV
• Voltage Regulation Accuracy: 1 %
• Maximum Operating Temperature: + 150 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Reference Voltage: 1.23 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

L4949E
3.5
3.6
Reset circuit
The block circuit diagram of the reset circuit is shown in
supervises the output voltage.
The reset threshold of 4.5 V is defined with the internal reference voltage and standby
output drivider.
The reset pulse delay time t
The reaction time of the reset circuit originates from the discharge time limitation of the reset
capacitor CT and is proportional to the value of CT.
The reaction time of the reset circuit increases the noise immunity. Standby output voltage
drops below the reset threshold only a bit longer than the reaction time results in a shorter
reset delay time.
The nominal reset delay time is generated for standby output voltage drops longer than
approximately 50ms.
The typical reset output waveforms are shown in
Sense comparator
The sense comparator compares an input signal with an internal voltage reference of typical
1.23V. The use of an external voltage divider makes this comparator very flexible in the
application.
It can be used to supervise the input voltage either before or after the protection diode and
to give additional informations to the microprocessor like low voltage warnings.
Figure 7.
t
RD
=
C
-------------------- -
T
2μA
•
2V
Block circuit of reset circuit
RD
, is defined with the charge time of an external capacitor C
Doc ID 4275 Rev 6
Figure
Figure
8.
7. The reset circuit
Application information
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T
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