LMS1587CT-ADJ/NOPB National Semiconductor, LMS1587CT-ADJ/NOPB Datasheet - Page 6

• Manufacturer Part Number: LMS1587CT-ADJ/NOPB
• Description: Linear Voltage Regulator IC
• Manufacturer: National Semiconductor
• Series: -r

Specifications of LMS1587CT-ADJ/NOPB

• Dropout Voltage, Vdo: 1.15V
• Input Voltage Primary Max: 13V
• Operating Temperature Range: 0°C To +125°C
• Output Current Max: 3000mA
• Output Voltage Adjustable Min, Vout: 1.25V
• Output Voltage Max: 5.75V
• Regulator Topology: Positive Adjustable
• Voltage - Output: 1.25 V ~ 5.7 V
• Voltage - Input: 2.5 V ~ 13 V
• Voltage - Dropout (typical): 1.15V @ 3A
• Number Of Regulators: 1
• Current - Output: 3A
• Current - Limit (min): 3.1A
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: *
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Note
OUTPUT VOLTAGE
The adjustable version develops at 1.25V reference voltage,
(V
), between the output and the adjust terminal. As
REF
shown in Figure 1, this voltage is applied across resistor R1
to generate a constant current I1. This constant current then
flows through R2. The resulting voltage drop across R2 adds
to the reference voltage to sets the desired output voltage.
The current I
from the adjustment terminal introduces an
ADJ
output error. But since it is small (120µA max), it becomes
negligible when R1 is in the 100Ω range.
For fixed voltage devices, R1 and R2 are integrated inside
the devices.
10119772
FIGURE 1. Basic Adjustable Regulator
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