tk11633utl Token Electronics Industry Co., Ltd., tk11633utl Datasheet - Page 12

• Manufacturer Part Number: tk11633utl
• Description: Three-terminal Voltage Regulator
• Manufacturer: Token Electronics Industry Co., Ltd.

INPUT/OUTPUT
CONSIDERATIONS
Voltage regulators require input and output decoupling
capacitors. The required value of these capacitors vary
with application. Capacitors made by different
manufacturers can have different characteristics,
particularly with regard to high frequencies and Equivalent
Series Resistance (ESR) over temperature. The type of
capacitor is also important. For example, a 4.7 F aluminum
electrolytic may be required for a certain application. If a
tantalum capacitor is used, a lower value of 2.2 F would
be adequate. It is important to consider the temperature
characteristics of the decoupling capacitors. While Toko
regulators are designed to operate as low as -30 C, many
capacitors will not operate properly at this temperature.
The capacitance of aluminum electrolytic capacitors may
decrease to 0 at low temperatures. This may cause
oscillation on the output of the regulator since some
capacitance is required to guarantee stability. Thus, it is
important to consider the characteristics of the capacitor
over temperature when selection decoupling capacitors.
The ESR is another important parameter. The ESR will
increase with temperature but low ESR capacitors are
often larger and more costly. In general, tantalum capacitors
offer lower ESR than aluminum electrolytic, but new low
ESR aluminum electrolytic capacitors are now available
from several manufacturers. Usually a bench test is
sufficient to determine the minimum capacitance required
for a particular application. After taking thermal
characteristics and tolerance into account, the minimum
capacitance value should be approximately two times this
value. Please note that linear regulators with a low dropout
voltage have high internal loop gains which require care in
guarding against oscillation caused by insufficient
decoupling capacitance. The use of high quality decoupling
capacitors suited for your application will guarantee proper
operation of the circuit.
TK116xxU
Page 12
DECOUPLING
APPLICATION INFORMATION
CAPACITOR
BOARD LAYOUT
Copper pattern should be as large as possible. Power
dissipation is 1000 mW for SOT-89. A low ESR capacitor
is recommended. For low temperature operation, select a
capacitor with a low ESR at the lowest operating
temperature to prevent oscillation, degradation of ripple
rejection and increase in noise. The minimum
recommended capacitance is 2.2 F.
+
V IN
SOT-89 BOARD LAYOUT
GND
December 1998 TOKO, Inc.
V OUT
+