MP2005 – 800mA, HIGH PSRR,ULDO LINEAR REGULATOR
MP2005 Rev. 1.0 www.MonolithicPower.com 9
3/17/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
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APPLICATION INFORMATION
Setting the Output Voltage
The MP2005 has an adjustable output voltage,
set by using a resistive voltage divider from the
output voltage to FB pin. The voltage divider
divides the output voltage down to the feedback
voltage by the ratio:
2R1R
2R
VV
OUTFB
Where V
FB
is the feedback threshold voltage
(V
FB
= 0.5V), and V
OUT
is the output voltage.
Thus the output voltage is:
2R
2R1R
5.0V
OUT
R2 can be as high as 100kΩ, but a typical value
is 10kΩ. Using that value, R1 is determined by:
FB
FBOUT
V
VV
2R1R
For example, for a 1.8V output voltage, R2 is
10kΩ, and R1 is 26kΩ. You can select a
standard 26kΩ (±1%) resistor for R1.
The following table lists the selected R1 for
various output voltages.
Table 1—Adjustable Output Voltages R1 Values
V
OUT
(V) R1 (kΩ) R2 (kΩ)
1.25 15
10
1.5 20
1.8 26
2 30
2.5 40
2.8 46
3 50
3.3 56
4 70
Bias Input
The bias input is designed for low drop
application. The bias pin must be at least 2.7V,
and at least 1.5V higher than the output. If V
IN
supply voltage meets these requirements, the
bias pin can be tied to V
IN.
Feed Forward Capacitor
Feed forward capacitor which a ceramic type
capacitor parallels with R1 affects loop stability.
According to actual application, MP2005
improves load transient performance by add a
suitable feed forward capacitor.
