MAX727 datasheet(3/4 Pages) MAXIM

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5V/3.3V/3V 5A Step-Down, PWM,

Switch-Mode DC-DC Regulators

_______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN = 25V, Tj = TMIN to TMAX, unless otherwise noted.)

PARAMETER

MIN

TYP

MAX

UNITS

4.85

5.00

5.15

3.20

3.30

3.40

SENSE Voltage

VC = 2V

2.90

3.00

3.10

3.0

5.0

8.0

Ω

2.5

4.2

7.0

SENSE Pin Divider Resistance

Tj = +25°C

2.2

3.8

6.5

CONDITIONS

MAX787

MAX788

MAX789

MAX787

MAX788

MAX789

Tj = +25°C

±0.5

±2.0

Output Voltage Tolerance

VOUT (nominal) = 5V (MAX787),

3.3V (MAX788), or 3V (MAX789);

all conditions of input voltage,

output voltage, and load

current

Tj = TMIN to

TMAX

±1.0

±3.0

≤ VIN ≤ 40V

0.005

0.020

%/V

Output Voltage Line Regulation

Tj = +25°C

1.5

VC Voltage

Tj = TMIN to TMAX

-4

2.5

°C/W

Thermal Resistance Junction to Case

(Note 6)

mV/°C

VC Voltage Temperature Coefficient

0% duty cycle

Note 1: Do not exceed switch-to-input voltage limitation.

Note 2: For switch currents between 1A and 5A, maximum switch-on voltage can be calculated via linear interpolation.

Note 3: By setting the SENSE pin to 5.5V, the VC pin is forced to its low clamp level and the switch duty cycle is forced to zero,

approximating the zero load condition.

Note 4: For proper regulation, total voltage from VIN to GND must be ≥ 8V after start-up.

Note 5: To avoid extremely short switch-on times, the switch frequency is internally scaled down when VSENSE is less than 2.6V

(MAX787), 2.0V (MAX788), or 1.8V (MAX789). Switch-current limit is tested with VSENSE adjusted to give a 1µs minimum

switch-on time.

Note 6: Guaranteed, not production tested.

______________________________________________________________Pin Description

VIN supplies power to the internal circuitry and also connects to the collector of the internal power

switch. VIN must be bypassed with a low-ESR capacitor, typically 200µF or 220µF.

Internal Power Switch Output. The Switch output can swing 35V below ground and is rated for 5A.

Ground requires a short, low-noise connection to ensure good load regulation. The internal reference

is referred to GND, so errors at this pin are multiplied by the error amplifier.

Error-Amplifier Output. A series RC network connected to this pin compensates the MAX787/MAX788/

MAX789. Output swing is limited to about 5.8V in the positive direction and -0.7V in the negative direc-

tion. VC can also synchronize the MAX787/MAX788/MAX789 to an external TTL clock in the 115kHz to

170kHz range. See MAX724/MAX726 data sheet.

SENSE Input is the internal error amplifier's input, and should be directly connected to VOUT. SENSE

also aids current limiting by reducing oscillator frequency when VOUT is low.

VIN

VSW

GND

SENSE

NAME

FUNCTION

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