NCV8505 ON Semiconductor, NCV8505 Datasheet - Page 10

• Manufacturer Part Number: NCV8505
• Description: Micropower 400 mA LDO Linear Regulators
• Manufacturer: ON Semiconductor

Voltage, Delay Switching Threshold, and the Delay Charge
Current. The delay follows the equation:
Example:
three main characteristics of a linear regulator: start−up
delay, load transient response and loop stability.
availability, size and temperature constraints. A tantalum or
aluminum electrolytic capacitor is best, since a film or
ceramic capacitor with almost zero ESR can cause
instability. The aluminum electrolytic capacitor is the least
expensive solution, but, if the circuit operates at low
temperatures (−25°C to −40°C), both the value and ESR of
the capacitor will vary considerably. The capacitor
manufacturers data sheet usually provides this information.
should work for most applications, however it is not
necessarily the optimized solution.
regulator (Figure 19) is:
V
**C
t DELAY +
IN
*C
0.1 mF
temperature expected.
The delay time is controlled by the Reset Delay Low
Using C
Assume reset Delay Low Voltage = 0.
Use the typical value for V
Use the typical value for Delay Charge Current = 4.2 mA.
The output or compensation capacitor helps determine
The capacitor value and type should be based on cost,
The value for the output capacitor C
The maximum power dissipation for a single output
C
filter.
OUT
Figure 18. Test and Application Circuit Showing
IN
IN
CALCULATING POWER DISSIPATION IN A
*
required if regulator is located far from the power supply
SINGLE OUTPUT LINEAR REGULATOR
required for stability. Capacitor must operate at minimum
5.0 V options).
t DELAY +
DELAY
STABILITY CONSIDERATIONS
[ C DELAY (V dt * Reset Delay Low Voltage) ]
SETTING THE DELAY TIME
Output Compensation
= 33 nF.
NCV8505
[ 33 nF(1.8 * 0) ]
Delay Charge Current
RESET
4.2 mA
V
OUT
dt
= 1.8 V (2.5 V, 3.3 V, and
OUT
+ 14 ms
R
RST
shown in Figure 18
APPLICATION NOTES
33 mF
C
http://onsemi.com
OUT
**
10
P D(max) + [V IN(max) * V OUT(min) ] I OUT(max)
where:
permissible value of R
package section of the data sheet. Those packages with
R
the die temperature below 150°C.
dissipate the heat generated by the IC, and an external
heatsink will be required.
package to improve the flow of heat away from the IC and
into the surrounding air.
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed to
determine the value of R
where:
R
functions of the package type, heatsink and the interface
between them. These values appear in heat sink data sheets
of heat sink manufacturers.
qJA
qJA
V
V
I
application, and
I
I
Once the value of P
The value of R
In some cases, none of the packages will be sufficient to
A heat sink effectively increases the surface area of the
Each material in the heat flow path between the IC and the
R
R
R
R
OUT(max)
Q
OUT(max)
qJC
qCS
qSA
qJC
IN(max)
OUT(min)
’s less than the calculated value in equation 2 will keep
, it too is a function of package type. R
is the quiescent current the regulator consumes at
V
Figure 19. Single Output Regulator with Key
IN
= the junction−to−case thermal resistance,
appears in the package section of the data sheet. Like
= the case−to−heatsink thermal resistance, and
= the heatsink−to−ambient thermal resistance.
Performance Parameters Labeled
R qJA + R qJC ) R qCS ) R qSA
is the maximum input voltage,
.
) V IN(max) I Q
is the minimum output voltage,
is the maximum output current for the
I
IN
qJA
R qJA + 150°C *
can then be compared with those in the
HEAT SINKS
qJA
REGULATOR®
D(max)
qJA
}
can be calculated:
SMART
Control
Features
:
P D
is known, the maximum
I
Q
T A
qCS
I
OUT
and R
qSA
V
OUT
are
(1)
(2)
(3)