MAX6773BTASD2+T Datasheet MAX6767TALD2+T, MAX6765TTSD2+T, MAX6765TTLD2+T | P16-P18

MAX6765–MAX6774

Automotive Micropower Linear Regulators

with Supervisor

Maxim Integrated

Watchdog Timer (MAX6773/MAX6773B/

MAX6774/MAX6774B)

The MAX6773/MAX6774 include a watchdog timer that

asserts RESET if the watchdog input (WDI) does not

toggle within the watchdog timeout period, t

(1.6s

(typ) for the MAX6773/MAX6774 and 50ms (typ) for the

MAX6773B/MAX6774B). RESET remains low for the

reset timeout period, t

. If the watchdog is not updat-

ed for lengthy periods of time, the reset output appears

as a pulse train, asserted for the reset timeout period

and deasserted for the watchdog timeout period, until

WDI is toggled again. When RESET asserts, it stays low

for the entire reset timeout period ignoring any WDI

transitions. To prevent the watchdog from asserting

RESET, toggle WDI with a valid rising or falling edge

prior to t

(min). The watchdog counter clears when

WDI toggles prior to t

or when RESET asserts. The

watchdog resumes counting after RESET deasserts.

The watchdog timer cannot be disabled.

Thermal Protection

When the junction temperature exceeds T

= +160°C

(typ), an internal thermal sensor signals the shutdown

logic that turns off the pass transistor and allows the IC

to cool. The thermal sensor turns the pass transistor on

again after the IC’s junction temperature cools by 20°C

(typ), resulting in a cycled output during continuous

thermal-overload conditions. Thermal protection pro-

tects the MAX6765–MAX6774B in the event of a fault

condition. Never exceed the absolute maximum junction

temperature rating of T

= +150°C. See Figures 3 and 4

for the safe operating area.

Applications Information

Output-Voltage Selection

The MAX6767–MAX6774B feature dual-mode operation

and operate in either a preset or adjustable voltage

mode. In preset voltage mode, internal trimmed feed-

back resistors set the internal linear regulator to +1.8V,

+2.5V, +3.3V, or +5V (see Table 2). Select preset-

voltage mode by connecting SET to ground. In

adjustable mode, select an output voltage between

+1.8V and +11V using two external resistors connected

as a voltage-divider to SET (see Figure 1). Set the output

voltage using the following equation:

OUT

= V

SET

(1 + R1/R2)

where V

SET

= 1.233V and the recommended value for

R2 is 50kΩ (maximum 100kΩ).

RESETIN Threshold Selection

The MAX6769/MAX6770 feature an adjustable reset

threshold to monitor the voltage on RESETIN using a

resistive divider between the monitored voltage,

RESETIN and GND. See Figure 2. Use the following

formula to set the desired reset threshold:

MON

= V

(1 + R3/R4)

where V

is 1.085V for the M/S/Y/V versions and

1.147V for the L/T/Z/W versions.

MAX6769

MAX6770

RESETRESETIN

GND

MON

Figure 2. RESETIN Threshold Selection

OPERATING

STATE

ENABLE HOLD

REGULATOR

OUTPUT

COMMENT

Initial State Low Don’t care Off

ENABLE is pulled to GND through an internal pulldown. HOLD is high

impedance (pulled up to OUT). Regulator output is disabled.

Turn-On State High Don’t care On

ENABLE is externally driven high turning the regulator output on.

HOLD is pulled up by OUT.

Hold

Setup State

High Low On

HOLD is externally pulled low while ENABLE remains high (latches

HOLD state).

Hold State Low Low On

ENABLE is driven low (or pulled low by an internal pulldown).

HOLD remains externally pulled low keeping the regulator output on.

Off-State Low

High

(pulled high)

Off

HOLD is driven high (or pulled high by an internal pullup) while

ENABLE is low. Regulator output is shut off and ENABLE/

HOLD logic returns to the initial state.

Table 3. ENABLE/HOLD Truth Table/State Table

MAX6765–MAX6774

Automotive Micropower Linear Regulators

with Supervisor

Maxim Integrated

Available Output-Current Calculation

The MAX6765–MAX6774B 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–MAX6774B, respectively. The

graph assumes that the exposed metal pad of the

device package is soldered to a solid 1in

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:

MAX

= Max. Power Dissip = 1.951W, for T

≤ +70°C

MAX

= Max. Power Dissip = [1.9W - 0.0244W x

- 70°C)], for +70°C < T

≤ +125°C

where 0.0244W is the MAX6767–MAX6774B package

thermal derating in W/°C and T

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

- 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.

= C

TIMEOUT

x 1.22 x 10

Ω (L/M/T/S options)

= C

TIMEOUT

x 1.17 x 10

Ω (V/W/Y/Z options)

where t

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

recommended; 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.

MAX6765 fig03

TEMPERATURE (°C)

PD (W)

14012080 10040 6020

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

0 160

DERATE 23.8mW/°C

ABOVE +70°C

1.904W

SAFE OPERATING

AREA

MAX6765 fig04

TEMPERATURE (°C)

PD (W)

14012080 10040 6020

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

0 160

DERATE 24.4mW/°C

ABOVE +70°C

1.951W

SAFE OPERATING

AREA

Figure 3. Maximum Power Dissipation vs. Temperature

(MAX6765/MAX6766)

Figure 4. Maximum Power Dissipation vs. Temperature

(MAX6767–MAX6774B)

MAX6765–MAX6774

Automotive Micropower Linear Regulators

with Supervisor

Maxim Integrated

Ensuring a Valid

RESET

Output Down to

= 0V (MAX6766/MAX6768/MAX6770/

MAX6772/MAX6774/MAX6774B)

When V

falls below 1V, RESET current-sinking capa-

bilities decline drastically. High-impedance CMOS-

logic inputs connected to RESET can drift to

undetermined voltages. This presents no problems in

most applications, since most µPs and other circuitry

do not operate with supply voltages below 1V. In appli-

cations where RESET must be valid down to 0V, adding

a pulldown resistor between RESET and ground sinks

any stray leakage currents, holding RESET low (Figure

5). The value of the pulldown resistor is not critical;

100kΩ is large enough not to load RESET and small

enough to pull RESET to ground. Open-drain RESET

versions are not recommended for applications requir-

ing valid logic for V

down to 0V.

PART

OUTPUT

VOLTAGE (V)

RESET

TIMEOUT

PERIOD (ms)

RESET

THRESHOLD

(V)

RESETIN

THRESHOLD

(V)

TOP MARK

MAX6765TTLD2+T 5 12.5

4.625

— +AQB

MAX6765TTSD2+T 3.3 12.5

2.888

— +AQL

MAX6766TTLD2+T 5 12.5

4.625

— +ARO

MAX6766TTSD2+T 3.3 12.5

2.888

— +ARZ

MAX6767TALD2+T 5 12.5

4.625

— +AVI

MAX6767TASD2+T 3.3 12.5

2.888

— +AVS

MAX6768TALD2+T 5 12.5

4.625

— +AVZ

MAX6768TASD2+T 3.3 12.5

2.888

— +AXE

MAX6769TALD2+T 5 12.5

—

1.147 +AYH

MAX6769TASD2+T 3.3 12.5

—

1.085 +AYQ

MAX6770TALD2+T 5 12.5

—

1.147 +AZS

MAX6770TASD2+T 3.3 12.5

—

1.085 +BAC

MAX6771TALD2+T 5 12.5

4.625

— +BEG

MAX6771TASD2+T 3.3 12.5

2.888

— +BEQ

MAX6772TALD2+T 5 12.5

4.625

— +APY

MAX6772TASD2+T 3.3 12.5

2.888

— +BGC

MAX6773TALD2+T 5 12.5

4.625

— +BBG

MAX6773TASD2+T 3.3 12.5

2.888

— +AQE

MAX6773BTALD2+T 5 12.5

4.625

— +BHK

MAX6773BTASD2+T 3.3 12.5

2.888

— +BHU

MAX6774TALD2+T 5 12.5

4.625

— +BCS

MAX6774TASD2+T 3.3 12.5

2.888

— +BDC

MAX6774BTALD2+T 5 12.5

4.625

— +BIY

MAX6774BTASD2+T 3.3 12.5

2.888

— +BJI

Table 4. Standard Version Part Numbers

MAX6766

MAX6768

MAX6770

MAX6772

MAX6774

MAX6774B

RESET

GND

Figure 5. Ensuring RESET Valid to V

= 0V

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P22

MAX6773BTASD2+T

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Linear Voltage Regulators uPower Linear Regulator

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MAX6773BTASD2+T

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