L4979D STMicroelectronics, L4979D Datasheet - Page 10

• Manufacturer Part Number: L4979D
• Description: IC VOLTAGE REG LDO SO-8
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L4979D

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 5V
• Current - Output: 150mA
• Voltage - Input: 5.6 ~ 31 V
• Operating Temperature: -40°C ~ 150°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Polarity: Positive
• Input Voltage Max: 31 V
• Output Voltage: 5 V
• Output Type: Fixed
• Dropout Voltage (max): 0.4 V at 150 mA
• Output Current: 300 mA
• Line Regulation: 25 mV
• Load Regulation: 25 mV
• Voltage Regulation Accuracy: 2 %
• Maximum Operating Temperature: + 150 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

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3.1
3.2
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Application informations
Voltage regulator
The voltage regulator uses a p-channel MOS transistor as a regulating element. With this
structure a low dropout voltage at current up to 150 mA is achieved. The output voltage is
regulated up to transient input supply voltage of 40 V. No functional interruption due to over-
voltage pulses is generated. The high precision of the output voltage is obtained with a pre-
trimmed reference voltage. A short circuit protection to GND is provided.
Figure 3.
Reset
The reset circuit monitors the output voltage V
R
delta (V
1 V.
When the output voltage becomes higher than V
delay is obtained by 512 periods of an oscillator (see fig. 5). The oscillator period is given by:
and reset pulse delay t
es
becomes low with a delay time t
o-th
- V
Behavior of output current versus regulated voltage V
o
). The reset low signal is guaranteed for an output voltage V
T
OSC
rd
is given by:
=
[
------------------------------------------------------ -
(
V
Doc ID 10262 Rev 7
rhth
rr
–
t
. Real t
rd
I
V
cr
rlth
=
) C
512
⋅
rr
o
value changes as a non-linear function of
. If the output voltage drops below V
tr
×
o_th
]
T
+
OSC
then R
[
------------------------------------------------------ -
(
V
rhth
es
–
I
goes high with a delay t
V
dr
rlth
) C
⋅
tr
o
]
o
greater than
o_th
rd
. This
then