Datasheet

Applications Information
Output Voltage Selection
The MAX5086 features dual-mode operation, in either
a preset voltage mode or an adjustable mode. In pre-
set voltage mode, internal feedback resistors set the
MAX5086’s output voltage to +3.3V or +5V. Select preset
voltage mode by connecting SET to ground. In adjustable
mode, select an output between +2.5V and +11V using
two external resistors connected as a voltage-divider to
SET (Figure 2). Set the output voltage using the following
equation:
OUT SET
R1
V V x 1
R2

= +


where V
SET
= 1.23V and R2 is chosen to be approxi-
mately 100kΩ.
Available Output Current Calculation
The MAX5086 high-voltage regulator provides up to
250mA of output current. The input voltage extends to
+45V. Package power dissipation limits the amount of
output current available for a given input/output voltage
and ambient temperature. Figure 3 depicts the maximum
power dissipation curve for these devices. The graph
assumes that the exposed pad of the MAX5086 package
is set up per JEDEC specifications.
Use Figure 3 to determine the allowable package dissipa-
tion (P
D
) for a given ambient temperature. Alternately, use
the following formula to calculate the allowable package
dissipation:
A
DA
A
2.666W for T 70 C
W
P 2.666W 0.0333 x (T 70 C)
C
For 70 C T 125 C
≤+ °



= − −°

°


+ ° < ≤+ °

After determining the allowable package dissipation
calculate the maximum output current using the following
formula:
D
OUT(MAX)
IN OUT
P
I 250mA
VV
≅≤
−
The above equations do not include the negligible power
dissipation from self-heating due to the IC ground current.
Example 1:
T
A
= +85°C
V
IN
= +14V
V
OUT
= +5V
Find the maximum allowable output current. First cal-
culate package dissipation at the given temperature as
follows:
D
W
P 2.666W 0.0333 (85 C 70 C) 2.1665W
C
= − °−° =
°
Then determine the maximum output current:
OUT(MAX)
(2.1665W)
I 271mA
(14V) (5V)
= =
−
Figure 3. Calculated Maximum Power Dissipation vs.
Temperature
MAXIMUM POWER DISSIPATION
vs. TEMPERATURE
MAX5086 fig03
TEMPERATURE (°C)
P
D
(W)
12020 60 80 10040
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0
0 140
2.666W
DERATE
33.3mW/°C
MAX5086 45V, 250mA, Low-Quiescent-Current
Linear Regulator with Adjustable Reset Delay
www.maximintegrated.com
Maxim Integrated │ 9