65V, Low-Quiescent-Current, High-Voltage Linear
Regulators with µP Reset and Watchdog Timer
Example 1:
MAXIMUM OUTPUT CURRENT
T = +95°C
A
vs. INPUT VOLTAGE
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
V
V
= +14V
IN
V
= +5V
OUT
DEVICE EXPOSED
PAD SOLDERED TO
= +5V
OUT
2
Find the maximum allowable output current. First calcu-
late package dissipation at the given temperature as
follows:
1IN COPPER ISLAND
T = +70°C
A
T = +85°C
A
P = 1.538W - 0.01923W/°C 95°C - 70°C
(
) (
)
D
=1.057W
T = +125°C
A
Then determine the maximum output current:
1.057W
0
5 10 15 20 25 30 35 40 45 50 55 60 65 70
(V)
(
)
=117.4mA
I
=
OUT MAX
V
IN
(
)
14V - 5V
) (
(
)
Figure 6. Maximum Output Current vs. Input Voltage
Example 2:
T = +125°C
A
V
= +14V
In Example 3, the maximum output current is calculated
as 170.9mA, however, the maximum output current
cannot exceed 150mA. Use Figure 6 to quickly deter-
mine allowable maximum output current for selected
ambient temperatures.
IN
OUT
V
= +3.3V
Calculate package dissipation at the given temperature
as follows:
P = 1.538W - 0.01923W/°C 125°C-70°C
(
) (
)
D
Capacitor Selection and Regulator
Stability
= 480.4mW
For stable operation over the full temperature range
and with load currents up to 150mA, use a 15µF (min)
output capacitor with an ESR < 0.5Ω. To reduce noise
and improve load-transient response, stability, and
power-supply rejection, use larger output capacitor val-
ues such as 22µF.
And establish the maximum current:
480.4mW
(
)
= 44.89mA
I
=
OUT MAX
(
)
14V - 3.3V
) (
(
)
Example 3:
T = +50°C
Some ceramic dielectrics exhibit large capacitance
and ESR variation with temperature. For dielectric
capacitors such as Z5U and Y5V, use 22µF or more to
ensure stability at temperatures below -10°C. With X7R
or X5R dielectrics, 15µF should be sufficient at all oper-
ating temperatures. For high-ESR tantalum capacitors
use 22µF or more to maintain stability. To improve
power-supply rejection and transient response use a
minimum 10µF capacitor between IN and GND.
A
V
V
= +14V
IN
= +5V
OUT
Calculate package dissipation at the given temperature
as follows:
P
D
= 1.538W
And find the maximum output current:
1.538W
(
)
=170.9mA⇒I
I
=
=150mA
OUT MAX
OUT MAX
(
)
(
)
14V - 5V
) (
(
)
______________________________________________________________________________________ 11
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
