R1121N_17 Datasheet, PDF (16/18 Pages) RICOH electronics devices division – LOW NOISE 150mA LDO REGULATOR

R1121N
TECHNICAL NOTES
When using these ICs, be sure to consider the following points:
In these ICs, phase compensation is made for securing stable operation even if the load current is varied. For
this purpose, be sure to use a capacitor COUT with good frequency characteristics and ESR (Equivalent Series
Resistance) in the range described as follows:
4 CE Vout 1
Ceramic
R1121N301B _Capacitor
3 _Vin
GND
2
Vin
Ceramic Capacitor
1μF
ESR
Iout
Spectrum
S.A. _Analyzer
Measuring Circuit for white noise; R1121N301B
The relationship between IOUT (output current) and ESR of output capacitor is shown in the graphs below. The
conditions when the white noise level is under 40mV (Avg.) are indicated by the hatched area in the graph.
(note: When the additional ceramic capacitors are connected to the output pin with output capacitor for phase
compensation, the operation might be unstable. Because of this, test these ICs with as the same external
components as the ones to be used on the PCB.)
<Measurement conditions>
(1) VIN=4V
(2) Frequency Band: 10Hz to 1MHz
(3) Temperature: 25°C
100.0
R1121N301B
Ceramic 1.0μF
100.0
R1121N301B
Ceramic 2.2μF
10.0
10.0
1.0
1.0
0.1
0
50
100
150
Output Current IOUT (mA)
0.1
0
50
100
150
Output Current IOUT (mA)
16