MIC5159-1.8YM6 MICREL [Micrel Semiconductor], MIC5159-1.8YM6 Datasheet - Page 9

• Manufacturer Part Number: MIC5159-1.8YM6
• Description: Programmable Current Limit ?Cap LDO Regulator Controller
• Manufacturer: MICREL [Micrel Semiconductor]

Input Capacitor
An input capacitor of 1.0µF or greater is recommended
when the device is more than 4 inches away from the
bulk AC supply capacitance or when the supply is a
battery. Small, surface mount, ceramic capacitors can be
used for bypassing the input to the regulator, further
improving the integrity of the output voltage. Larger input
capacitors
impedance of
requirements.
Layout Considerations
Input and output capacitor placement should be as close
as possible to the input and output, respectively. Trace
resistance between the current sense and the MOSFET
source should be minimized. Trace resistance will
increase dropout voltage. This is more of a factor at
higher output currents.
Also, a minimum amount of distance between the gate
pin, on the MIC5159, and the P-Channel MOSFET gate
is recommended. A long trace can create a small
parasitic inductor. This, coupled to the gate capacitance
of the MOSFET, can create a high frequency tank circuit.
A small 50Ω resistor in series with the gate may be
required to eliminate high-frequency noise.
Micrel, Inc.
June 2006
may
the
be
source and
required
depending
the
output
on
load
the
9
Adjustable Regulator Design
The MIC5159 allows programming the output voltage
anywhere between 1.235V to V
used. See Figure 4. The resistor values are calculated
by:
Where V
V
IN
R
R1
OUT
S
Figure 4. Adjustable Regulator Design
=
is the desired output voltage.
R2
IS
IN
EN
×
MIC5159-x.x
⎛
⎜
⎜
⎝
⎛
⎜ ⎜
⎝
GND
1.235
V
OUT
GATE
ADJ
⎞
⎟ ⎟
⎠
−
Si3445
1
⎞
⎟
⎟
⎠
IN
. Two resistors are
R1
R2
M9999-062706
C
ceramic
V
OUT
OUT
MIC5159
= 10µF