RT9164CGG Richtek USA Inc, RT9164CGG Datasheet - Page 8

• Manufacturer Part Number: RT9164CGG
• Description: IC REG LDO ADJ 1A SOT223
• Manufacturer: Richtek USA Inc

Specifications of RT9164CGG

• Regulator Topology: Positive Adjustable
• Voltage - Output: Adj to 1.25V
• Voltage - Input: 3 V ~ 12 V
• Voltage - Dropout (typical): 1.3V @ 1A
• Number Of Regulators: 1
• Current - Output: 1A (Max)
• Current - Limit (min): 1A
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: TO-261-4, TO-261AA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RT9164C
Input Bypass Capacitor
An input capacitor is recommended. A 10μF tantalum on
the input is a suitable input bypassing for almost all
applications.
Adjust Terminal Bypass Capacitor
The adjust terminal can be bypassed to ground with a
bypass capacitor (C
bypass capacitor prevents ripple from being amplified as
the output voltage is increased. At any ripple frequency,
the impedance of the C
the ripple from being amplified:
(2π x f
The R1 is the resistor between the output and the adjust
pin. Its value is normally in the range of 100-200Ω. For
example, with R1 = 124Ω and f
should be > 11μF.
www.richtek.com
8
Application Information
Output voltage adjustment
Like most regulators, the RT9164C regulates the output
by comparing the output voltage to an internally generated
reference voltage. On the adjustable version as shown in
Figure 4, the V
V
should be set to conduct 10mA (minimum output load).
The output voltage is given by the following equation:
V
On fixed versions of RT9164C, the voltage divider is provided
internally.
V
IN
OUT
OUT
10uF
C
= V
IN
and ADJ. The voltage ratio formed by R1 and R2
RIPPLE
REF
Figure 4. Basic Adjustable Regulator
x C
(1+
VIN
REF
65uA
I
ADJ
ADJ
RT9164C
R
R
is available externally as 1.25V between
2
1
) < R1
ADJ
ADJ
ADJ
) + I
) to improve ripple rejection. This
VOUT
should be less than R1 to prevent
ADJ
C
R
RIPPLE
ADJ
V
2
REF
= 120Hz, the C
R1
R2
10uF
C
OUT
V
OUT
ADJ
Output Capacitor
RT9164C requires a capacitor from V
compensation feedback to the internal gain stage. This is
to ensure stability at the output terminal. Typically, 10μF
tantalum or 50μF aluminum
range capacitor is sufficient.
The output capacitor does not
limit and increasing its value will increase stability.
C
design.
Load Regulation
When the adjustable regulator is
load regulation is accomplished when the top of the resistor
divider (R1) is connected directly to the output pin of the
RT9164C. When so connected, R
the divider ratio. For Fixed output version, the top of R1 is
internally connected to the output and ground pins can be
connected to low side of the load.
OUT
0.01
V
Figure 6. Best Load Regulation Using Adjustable
0.1
IN
10
= 100μF or more is typical for high current regulator
Region of Stable C
1
0
0.2
VIN
C
C
OUT
OUT
RT9164C
Output Regulator
ADJ
= 100uF
= 10uF
Load Current (A)
Figure 5
VOUT
0.4
OUT
electrolytic with 30mΩ to 2Ω
ESR vs. Load Current
have a theoretical upper
used (Figure 6), the
DS9164C-02 April 2010
R
Line Resistance
0.6
P
Instable
Stable
Instable
P
OUT
Parasitic
(Connect R1 to VOUT
or case)
R1
R2
is not multiplied by
Connect R2 to load
to GND to provide
0.8
R
L
best
1