RT9164-25CG Ver la hoja de datos (PDF) - Unspecified
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RT9164-25CG Datasheet PDF : 12 Pages
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RT9164
Application Information
Output voltage adjustment
Like most regulators, the RT9164 regulates the
output by comparing the output voltage to an
internally generated reference voltage. On the
adjustable version as shown in Fig.4, the VREF is
available externally as 1.25V between VOUT and
ADJ. The voltage ratio formed by R1 and R2 should
be set to conduct 10mA (minumum output load).
The output voltage is given by the following
equation:
VOUT = VREF (1+
R1
R2
) + IADJ × R2
On fixed versions of RT9164, the voltage divider is
provided internally.
VIN
10µF +
RT9164
VIN VOUT
ADJ
VREF R1
IADJ
65µA
+
R2
CADJ
VOU T
+ 10µF
Fig. 4 Basic Adjustable Regulator
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 (CADJ) to improve ripple rejection.
This bypass capacitor prevents ripple from being
amplified as the output voltage is increased. At any
ripple frequency, the impedance of the CADJ should
be less than R1 to prevent the ripple from being
amplified:
(2π * fRIPPLE * CADJ) < R1
The R1 is the resistor between the output and the
adjust pin. Its value is normally in the range of 100-
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200Ω. For example, with R1 = 124Ω and fRIPPLE =
120Hz, the CADJ should be > 11µF.
Output Capacitor
RT9164 requires a capacitor from VOUT to GND to
provide compensation feedback to the internal gain
stage. This is to ensure stability at the output
terminal. Typically, a 10µF tantalum or 50µF
aluminum electrolytic is sufficient.
Note: It is important that the ESR for this capacitor
does not exceed 0.5Ω.
The output capacitor does not have a theoretical
upper limit and increasing its value will increase
stability. COUT = 100µF or more is typical for high
current regulator design.
Load Regulation
When the adjustable regulator is used (Fig.5), the
best load regulation is accomplished when the top of
the resistor divider (R1) is connected directly to the
output pin of the RT9164. When so connected, RP is
not multiplied by 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.
RT9164
RP Parasitic
Line Resistance
VIN
VIN VOUT
GND
R1
(Connect R1
to case R2)
RL
R2
Connect R2 to load
Fig. 5 Best Load Regulation Using Adjustable Output
Regulator
Thermal Protection
RT9164 has thermal protection which limits junction
temperature to 150°C. However, device functionality
DS9164-08 May 2001
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