MAX6765 Datasheet, PDF (17/23 Pages) Maxim Integrated Products – Automotive Micropower Linear Regulators with Supervisor

Automotive Micropower Linear Regulators
with Supervisor
Available Output-Current Calculation
The MAX6765–MAX6774 provide up to 100mA of load
current. Package power dissipation limits the amount of
output current available for a given input/output voltage
and ambient temperature. Figures 3 and 4 depict the
maximum power dissipation curve for the MAX6765/
MAX6766 and MAX6767–MAX6774, respectively. The
graph assumes that the exposed metal pad of the
device package is soldered to a solid 1in² section of
2oz. PCB copper (JESD51-3 AND JESD51-5). Use
Figure 4 to determine the allowable package dissipa-
tion for a given ambient temperature. Alternately, use
the following formula to calculate the allowable pack-
age dissipation:
PD_MAX = Max. Power Dissip = 1.951W, for T_A ≤ +70°C
PD_MAX = Max. Power Dissip = [1.9W - 0.0244W x
(T_A - 70°C)], for +70°C < T_A ≤ +125°C
where 0.0244W is the MAX6767–MAX6774 package
thermal derating in W/°C and T_A is the ambient tempera-
ture in °C, under the same conditions used for Figure 4.
After determining the allowable package dissipation,
calculate the maximum output current using the follow-
ing formula:
PD < PD_MAX where PD = [(V_IN - V_OUT) x I_OUT]
Also, I_OUT should be ≤ 100mA in any case.
Selecting Timeout Capacitor
The reset timeout period is adjustable to accommodate
a variety of µP applications. Adjust the reset timeout
period by connecting a capacitor between TIMEOUT
and GND.
t_RP = C_TIMEOUT x 1.22 x 10⁶Ω
where t_RP is in seconds and C_TIMEOUT is in Farads.
Connect TIMEOUT to OUT to select the internally fixed
timeout period. C_TIMEOUT must be a low-leakage
(< 10nA) type capacitor. Ceramic capacitors are rec-
ommended; do not use capacitor values lower than
100pF to avoid the influence of parasitic capacitances.
Capacitor Selection and
Regulator Stability
For stable operation over the full temperature range and
with load currents up to 100mA, use a 10µF (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 values.
Some ceramic dielectrics exhibit large capacitance
and ESR variation with temperature. For dielectric
capacitors such as Z5U and Y5V, use more capaci-
tance to ensure stability at low temperatures. With X7R
or X5R dielectrics, 10µF should be sufficient at all oper-
ating temperatures. For higher-ESR tantalum capaci-
tors, use larger capacitor values to maintain stability. To
improve power-supply rejection and transient
response, use a larger capacitor than the minimum
0.1µF capacitor between IN and GND.
2.2 _1.904W
2.0
1.8
DERATE 23.8mW/°C
ABOVE +70°C
1.6
1.4
1.2
1.0
SAFE OPERATING
0.8
AREA
0.6
0.4
0.2
0
0 20 40 60 80 100 120 140 160
TEMPERATURE (°C)
Figure 3. Maximum Power Dissipation vs. Temperature
(MAX6765/MAX6766)
2.2 _1.951W
2.0
DERATE 24.4mW/°C
1.8 SAFE OPERATING ^{ABOVE +70°C}
1.6
AREA
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0 20 40 60 80 100 120 140 160
TEMPERATURE (°C)
Figure 4. Maximum Power Dissipation vs. Temperature
(MAX6767–MAX6774)
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