CS8361 Cherry Semiconductor Corporation, CS8361 Datasheet - Page 4

• Manufacturer Part Number: CS8361
• Description: 5V Dual Micropower Low Dropout Regulator with ENABLE and RESET
• Manufacturer: Cherry Semiconductor Corporation

Output capacitors for the CS8361 are required for stability.
Without them, the regulator outputs will oscillate. Actual
size and type may vary depending upon the application
load and temperature range. Capacitor effective series
resistance (ESR) is also a factor in the IC stability. Worst-
case is determined at the minimum ambient temperature
and maximum load expected.
Output capacitors can be increased in size to any desired
value above the minimum. One possible purpose of this
would be to maintain the output voltages during brief
conditions of negative input transients that might be char-
acteristic of a particular system.
Capacitors must also be rated at all ambient temperatures
expected in the system. To maintain regulator stability
down to -40ûC, capacitors rated at that temperature must
be used.
More information on capacitor selection for Smart
Regulatorsª is available in the Smart Regulator applica-
tion note, ÒCompensation for Linear Regulators.Ó
The maximum power dissipation for a dual output regula-
tor (Figure 1) is:
PD(max) = {V
Where
The
V
1.4V(typ), V
millivolts of hysteresis to prevent spurious output activity
during power-up or power-down.
The
trolled by a low voltage detection circuit sensing the V
(5V) output voltage. This circuit guarantees the
output stays below 1V (0.1V typ) when V
1V to ensure reliable operation of microprocessor-based
systems.
TRK
V
V
V
I
application
OUT1
IN
OUT1
OUT2
ENABLE
RESET
(max) is the maximum input voltage,
on and off. When the
(max) is the maximum output current, for the
(min) is the minimum output voltage from V
(min) is the minimum output voltage from V
{V
IN
TRK
IN
is an open collector NPN transistor, con-
in a Dual Output Linear Regulator
(max)ÐV
(max)ÐV
Calculating Power Dissipation
function switches the output transistor for
turns off. This input has several hundred
External Capacitors
ENABLE Function
OUT2
OUT1
RESET Function
(min)}I
(min)}I
ENABLE
OUT2
OUT1
(max)+V
(max)+
lead voltage exceeds
STBY
IN
(max)IQ
is as low as
RESET
Circuit Description
Application Notes
OUT1
OUT2
STBY
(1)
,
,
4
Once the value of PD(max) is known, the maximum per-
missible value of R
The value of R
the package section of the data sheet. Those packages
with R
will keep the die temperature below 150¡C.
In some cases, none of the packages will be sufficient to
dissipate the heat generated by the IC, and an external
heat sink will be required.
Figure 1: Dual output regulator with key performance parameters
labeled.
This output uses the same type of output device as V
but is rated for 250mA. The output is configured as a
tracking regulator of the standby output. By using the
standby output as a voltage reference, giving the user an
external programming lead (Adj lead), output voltages
from 5V to 20V are easily realized. The programming is
done with a simple resistor divider (Figure 2), and follow-
ing the formula:
If another 5V output is needed, simply connect the Adj
lead to the V
V
I
application
I
I
IN
OUT2
Q
OUT
is the quiescent current the regulator consumes at
(max).
QJA
(max) is the maximum output current, for the
I
IN
's less than the calculated value in equation 2
V
TRK
TRK
QJA
= V
output lead.
can then be compared with those in
QJA
STBY
V
}
R
Control
Features
TRK
QJA
Regulator
can be calculated:
Smart
´ (1 + R1/R2) + I
Output Voltage
=
150¡C - T
I
Q
P
D
A
I
I
OUT
OUT
Adj
2
1
´ R1
V
V
OUT
OUT
STBY
2
(2)
1
,