L4938ED STMicroelectronics, L4938ED Datasheet - Page 13

• Manufacturer Part Number: L4938ED
• Description: IC VREG ADVANCED DUAL SO-20
• Manufacturer: STMicroelectronics

Specifications of L4938ED

• Regulator Topology: Positive Fixed and Adjustable
• Voltage - Output: 5V, 4.9 ~ 5.1 V
• Voltage - Input: Up to 28V
• Voltage - Dropout (typical): 0.2V @ 100mA, 0.3V @ 400mA
• Number Of Regulators: 2
• Current - Output: 100mA, 400mA
• Current - Limit (min): 100mA, 450mA
• Operating Temperature: -40°C ~ 150°C
• Mounting Type: Surface Mount
• Package / Case: 20-SOIC (7.5mm Width)
• Polarity: Positive
• Number Of Outputs: 2
• Output Type: Fixed
• Output Voltage: 5 V
• Output Current: 5 mA
• Line Regulation: 20 mV
• Load Regulation: 50 mV
• Dropout Voltage (max): 0.2 V
• Input Voltage Max: 20 V
• Maximum Operating Temperature: + 150 C
• Minimum Operating Temperature: - 40 C
• Maximum Power Dissipation: 875 mW
• Mounting Style: SMD/SMT
• Reference Voltage: 1.23 V
• Voltage Regulation Accuracy: 2 %
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

L4938ED, L4938EPD
3.5
3.6
3.7
The value of the programming resistor R
The reset pulse delay time t
The reaction time of the reset circuit originates from 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 50 µs. The minimum reset time is generated if reset
condition only occurs for a short time triggering a reset pulse but not completely discharging
C
capacitor are required a resistors from pin C
We recommended the use of 10 KΩ to 5 V as an output pull up.
Sense comparator
The sense comparator compares an input signal with an internal voltage reference of typical
1.23 V. 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 information to the microprocessor like low voltage warnings. We
recommended the use of 10 KΩ to 5 V as an output pull up.
Thermal protection
Both outputs are provided with an overtemperature shutdown regulation power dissipation
down to uncritical values. Output 2 shuts down approximately 10 K before output 1. Under
normal conditions shutdown of output 2 allows the chip to cool down again. Thus output 1 is
unaffected. The thermal shutdown reduces the output voltages until power dissipation and
the flow of thermal energy out of the chip balance.
Transient sensitivity
In proper operation (V
sensitivity to input transients.
a. The reference is alternatively supplied from V
T
. The reset can be related to output2 on request. If higher charge currents for the reset
OUT
> 4.5 V) the reference is supplied by V
RD
, is defined with the charge time of an external capacitor C
Doc ID 17243 Rev 1
R
PR
t
t
RDnom
RDmin
3.8V
=
S
PR
or V
--------------------- - 92.9K
4.7K
----------- - 1
V
≤
RT
22K
V
can be calculated with:
T
=
=
OUT1
RT
to OUT1, may be used to increase the current.
C
------------------------
C
------------------------
–
T
. If one supply is present, the reference is operating.
≤
T
1μA
1μA
⋅
⋅
4.7V
–
0.6V
1.4V
OUT1
Application information
thus reducing
13/20
T
: