MAX5023 Datasheet, PDF (10/13 Pages) Maxim Integrated Products – 65V, Low-Quiescent-Current, High-Voltage Linear Regulators with μP Reset and Watchdog Timer

65V, Low-Quiescent-Current, High-Voltage Linear
Regulators with µP Reset and Watchdog Timer
Table 1. Truth Table for Regulator Output
State
ORDER EN HOLD OUT
COMMENTS
Initial state. EN has 5MΩ
1
Low
X
Off
internal resistor to ground.
HOLD has internal current
source to OUT.
2
High
X
On
Regulator output is active
when EN is pulled high.
Hold is asserted forcing the
3
High Low On regulator output on even if
EN goes low.
Self-holding state. Regulator
4
X Low On output stays on regardless of
the state of EN.
Regulator output is
5
Low High Off shutdown by releasing
HOLD while EN remains low.
X = Don’t care.
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 4). Set the output
voltage using the following equation:
V_OUT = V_SET (1 + R1 / R2)
where V_SET = 1.248V and R2 ≅ 100kΩ.
Available Output Current Calculation
The MAX5023/MAX5024 high-voltage regulator pro-
vides up to 150mA of output current. The input voltage
extends to +65V. Package power dissipation limits the
amount of output current available for a given input/
output voltage and ambient temperature. Figure 5
depicts the maximum power dissipation curve for these
devices. The graph assumes that the exposed metal
back of the MAX5023/MAX5024 package is soldered to
1in² of PC board copper.
Use Figure 5 to determine the allowable package dissi-
pation for a given ambient temperature. Alternately, use
the following formula to calculate the allowable pack-
age dissipation:
P_D
=
1.538W
_{1.538 -}
for T_A ≤ +70°C
0.01923 (T_A -70°C)
for + 70°C < T_A
≤ +125°C
+6.5V TO +65V
IN
10µF
ON
OFF
EN
OUT
MAX5024
HOLD
+2.5V TO +11V
15µF
R1
TO µP
SET
RESET
R2
GND
V_OUT = V_SET (1 + R1 / R2)
V_SET = 1.248V
R2 = 1kΩ TO 500kΩ
Figure 4. Setting the MAX5024 Adjustable Output Voltage
2.0
1.8
1.6
1.538W
1.4
1.2
1.0
0.8
0.6
0.4
0.2
DERATE
19.23mW/°C
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
T_A (°C)
Figure 5. Maximum Power Dissipation vs. Temperature
After determining the allowable package dissipation,
calculate the maximum output current using the follow-
ing formula:
I_OUT(MAX)
≅
V_IN
P_D
- V_OUT
≤ 150mA
The above equations do not include the negligible
power dissipation from self-heating due to the IC
ground current.
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