SI9185 Datasheet, PDF (10/12 Pages) Vishay Siliconix – Micropower 500-mA CMOS LDO Regulator

Si9185
Vishay Siliconix
BLOCK DIAGRAM
4
V_IN
SENSE
6
C_NOISE
1
8
SD
6 MW
RFB2
RFB1
+
–
To V_IN
60 mV
2 mA
+
+
–
3
GND
+
–
1.215 V
V_{REF –}
+
FIGURE 5.
5
V_OUT
2
DELAY
7
ERROR
DETAILED DESCRIPTION
The Si9185 is a low drop out, low quiescent current, and very
linear regulator family with very fast transient response. It is
primarily designed for battery powered applications where
battery run time is at a premium. The low quiescent current
allows extended standby time while low drop out voltage
enables the system to fully utilize battery power before
recharge. The Si9185 is a very fast regulator with bandwidth
exceeding 50 kHz while maintaining low quiescent current at
light load conditions. With this bandwidth, the Si9185 is the
fastest LDO available today. The Si9185 is stable with any
output capacitor type from 1 mF to 10.0 mF. However, X5R or
X7R ceramic capacitors are recommended for best output
noise and transient performance.
V_IN
V_IN is the input supply pin. The bypass capacitor for this pin
is not critical as long as the input supply has low enough source
impedance. For practical circuits, a 1.0-mF or larger ceramic
capacitor is recommended. When the source impedance is
not low enough and/or the source is several inches from the
Si9185, then a larger input bypass capacitor is needed. It is
required that the equivalent impedance (source impedance,
wire, and trace impedance in parallel with input bypass
capacitor impedance) must be smaller than the input
impedance of the Si9185 for stable operation. When the
source impedance, wire, and trace impedance are unknown,
it is recommended that an input bypass capacitor be used of
a value that is equal to or greater than the output capacitor.
V_OUT
V_OUT is the output voltage of the regulator. Connect a bypass
capacitor from V_OUT to ground. The output capacitor can be
any value from 1.0 mF to 10.0 mF. A ceramic capacitor with
X5R or X7R dielectric type is recommended for best output
noise, line transient, and load transient performance.
GND
Ground is the common ground connection for V_IN and V_OUT.
It is also the local ground connection for C_NOISE, DELAY,
SENSE or ADJ, and SD.
www.vishay.com
10
Document Number: 71765
S-20641—Rev. B, 06-May-02