Datasheet

 2017 Microchip Technology Inc. DS20005720A-page 13
MIC5209
larger output and bypass capacitors allows additional
time for the error amplifier and reference to turn on and
prevent overshoot.
To ensure that no overshoot is present when starting up
into a light load (100 µA), use a 4.7 µF output
capacitance and 470 pF bypass capacitance. This
slows the turn-on enough to allow the regulator to react
and keep the output voltage from exceeding its nominal
value. At heavier loads, use a 10 µF output
capacitance and 470 pF bypass capacitance. Lower
values of output and bypass capacitance can be used,
depending on the sensitivity of the system.
Applications that can withstand some overshoot on the
output of the regulator can reduce the output capacitor
and/or reduce or eliminate the bypass capacitor.
Applications that are not sensitive to overshoot due to
power-on reset delays can use normal output and
bypass capacitor configurations.
Please note the junction temperature range of the
regulator with an output less than 2.5V (fixed and
adjustable) is 0°C to +125°C.
4.8 Fixed Regulator Applications
Figure 4-1 shows a basic MIC5209-x.xYM (SOIC-8)
fixed-voltage regulator circuit. See Figure 5 for a similar
configuration using the more thermally-efficient
MIC5209-x.xYS (SOT-223). A 1 µF minimum output
capacitor is required for basic fixed-voltage
applications.
FIGURE 4-1: Low-Noise Fixed-Voltage
Application.
Figure 4-2 includes the optional 470 pF noise bypass
capacitor between BYP and GND to reduce output
noise. Note that the minimum value of C
OUT
must be
increased when the bypass capacitor is used.
FIGURE 4-2: Ultra-Low-Noise
Fixed-Voltage Application.
4.9 Adjustable Regulator Applications
The MIC5209YM, MIC5209YU, and MIC5209YML can
be adjusted to a specific output voltage by using two
external resistors (Figure 4-3). The resistors set the
output voltage based on the equation:
EQUATION 4-1:
This equation is correct due to the configuration of the
bandgap reference. The bandgap voltage is relative to
the output, as seen in the Functional Diagrams.
Traditional regulators normally have the reference
voltage relative to ground; therefore, their equations
are different from the equation for the MIC5209Y.
Although ADJ is a high-impedance input and, for best
performance, R2 should not exceed 470 kΩ.
FIGURE 4-3: Low-Noise
Adjustable-Voltage Application.
Figure 4-4 includes the optional 470 pF bypass
capacitor from ADJ to GND to reduce output noise.
FIGURE 4-4: Ultra-Low-Noise Adjustable
Application.
4.10 Slot-1 Power Supply
Intel’s Pentium II processors have a requirement for a
2.5V ±5% power supply for a clock synthesizer and its
associated loads. The current requirement for the 2.5V
supply is dependent upon the clock synthesizer used,
MIC5209-x.xYM
V
IN
1
2
3
4
5 - 8
IN
EN
OUT
BYP
GND
V
OUT
1μF
MIC5209-x.xYM
V
IN
1
2
3
4
5 - 8
IN
EN
OUT
BYP
GND
V
OUT
2.2μF
470pF
V
OUT
1.242V 1
R2
R1
------ -+


=
MIC5209YM
V
IN
1
2
3
4
5 - 8
IN
EN
OUT
ADJ
GND
V
OUT
1μF
R1
R2
MIC5209YM
V
IN
1
2
3
4
5 - 8
IN
EN
OUT
ADJ
GND
V
OUT
2.2μF
R1
R2
470pF