ILC7082 Datasheet, PDF (7/16 Pages) Impala Linear Corporation – 150MA SOT-23 ULTRA LOW NOISE CMOS RF-LDO REGULATOR

ILC7082
Note that there is a parasitic diode from the LDO regulator
output to the input. If the input voltage swings below the
regulator’s output voltage by 200mV then the regulator may
be damaged. This condition must be avoided. In many appli-
cations a large value input capacitor, C_IN, will hold V_IN
higher than V_OUT and decay slower than V_OUT when the
LDO is powered off.
Output Capacitor Selection
Fairchild strongly recommends the use of low ESR (equiva-
lent series resistance) ceramic capacitors for C_OUT and
C_NOISE The ILC7082 is stable with low ESR capacitor (as
low as zero Ω). The value of the output capacitor should be
1µF or higher. Either a ceramic chip or a tantalum capacitor
may be used at the output.
Use of ceramic chip capacitors offer significant advantages
over tantalum capacitors. A ceramic capacitor is typically
cheaper than a tantalum capacitor, it usually has a smaller
footprint, lower height, and lighter weight than a tantalum
capacitor. Furthermore, unlike tantalum capacitors which are
polarized and can be damaged if connected incorrectly,
ceramic capacitors are non-polarized. Low value ceramic
chip capacitors with X5R or X7R dielectric are available in
the 100pF to 4.7µF range. Beware of using ceramic capaci-
tors with Y5V dielectric since their ESR increases signifi-
cantly at cold temperatures. Table 1 shows a list of
recommended ceramic capacitors for use at the output of
ILC7082.
Note: If a tantalum output capacitor is used then for stable
operation we recommend a low ESR tantalum capacitor with
maximum rated ESR at or below 0.4Ω. Low ESR tantalum
capacitors, such as the TPS series from AVX Corporation
(www.avxcorp.com) or the T495 series from Kemet
(www.kemet.com) may be used.
In applications where a high output surge current can be
expected, use a high value but low ESR output capacitor for
superior load transient response. The ILC7082 is stable with
no load.
Noise Bypass Capacitor
In low noise applications, the ILC7082’s noise can be
decreased further by connecting a capacitor from the
noise bypass pin to ground. The noise bypass pin is a high
impedance node, and as such, care should be taken in printed
circuit board layout to avoid noise pick-up from external
sources. Moreover, the noise bypass capacitor should have
low leakage.
Noise bypass capacitors with a value as low as 470pF may
be used. However, for optimum performance, use a 0.01µF
or larger, ceramic chip capacitor. Note that the turn on and
turn off response of the ILC7082 is inversely proportional to
the value of the noise bypass capacitor. For fast turn on and
turn off, use a small value noise bypass capacitor. In appli-
cations were exceptionally low output noise is not required,
consider omitting the noise bypass capacitor altogether.
The Effects of ESR (Equivalent Series
Resistance)
The ESR of a capacitor is a measure of the resistance due to
the leads and the internal connections of the component.
Typically measured in mΩ (milli-ohms) it can increase to
ohms in some cases.
Wherever there is a combination of resistance and current,
voltages will be present. The control functions of LDOs use
two voltages in order to maintain the output precisely; V_OUT
and V_REF.
Table 1. Recommended Ceramic Output Capacitors
C_OUT
1µF
Capacitor Size
0805
I_OUT
0 to 150mA
Dielectric
X5R
Part Number
C2012X5R1A105KT
0805
X7R
GRM40X7R105K010
0805
X7R
LMK212BJ105KG
1206
X7R
GRM42-6X7R105K016
1206
X7R
EMK316BJ105KL
1206
X5R
TMK316BJ105KL
Capacitor Vendor
TDK
muRata
Taiyo-Yuden
muRata
Taiyo-Yuden
Taiyo-Yuden
2.2µF
0805
0805
1206
0 to 150mA
X5R
X5R
X5R
GRM40X5R225K 6.3
C2012X5R0J225KT
EMK316BJ225ML
muRata
TDK
Taiyo-Yuden
4.7µF
1206
1206
0 to 150mA
X5R
X7R
GRM42-6X5R475K010
LMK316BJ475ML
muRata
Taiyo-Yuden
REV. 1.6.2 11/17/04
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