MAX16936(2018) 查看數據表（PDF） - Maxim Integrated

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MAX16936
(Rev.:2018)

36V, 220kHz to 2.2MHz Step-Down Converters with 28µA Quiescent Current

Maxim Integrated 

MAX16936/MAX16938

36V, 220kHz to 2.2MHz Step-Down Converters

with 28µA Quiescent Current

Pin Descriptions (continued)

PIN

TSSOP

TQFN

10

9

11

10

12

13, 14

15

16

11

12, 13

14

15

—

—

NAME

EN

SUP

SUPSW

LX

PGND

PGOOD

EP

FUNCTION

SUP Voltage Compatible Enable Input. Drive EN low to disable the device. Drive EN high

to enable the device.

Voltage Supply Input. SUP powers up the internal linear regulator. Bypass SUP to PGND

with a 4.7FF ceramic capacitor. It is recommended to add a placeholder for an RC filter

to reduce noise on the internal logic supply (see the Typical Application Circuit)

Internal High-Side Switch Supply Input. SUPSW provides power to the internal switch.

Bypass SUPSW to PGND with 0.1FF and 4.7FF ceramic capacitors.

Inductor Switching Node. Connect a Schottky diode between LX and PGND.

Power Ground

Open-Drain, Active-Low Power-Good Output. PGOOD asserts when VOUT is above 95%

regulation point. PGOOD goes low when VOUT is below 92% regulation point.

Exposed Pad. Connect EP to a large-area contiguous copper ground plane for effective

power dissipation. Do not use as the only IC ground connection. EP must be connected

to PGND.

Detailed Description

The MAX16936/MAX16938 are 2.5A current-mode

step-down converters with integrated high-side and low-

side MOSFETs designed to operate with an external

Schottky diode for better efficiency. The low-side MOSFET

enables fixed-frequency forced-PWM (FPWM) operation

under light-load applications. The devices operate with

input voltages from 3.5V to 36V, while using only 28FA

quiescent current at no load. The switching frequency is

resistor programmable from 220kHz to 2.2MHz and can

be synchronized to an external clock. The output voltage

is available as 5V/3.3V fixed or adjustable from 1V to

10V. The wide input voltage range along with its ability to

operate at 98% duty cycle during undervoltage transients

make the devices ideal for automotive and industrial

applications.

Under light-load applications, the FSYNC logic input allows

the device to either operate in skip mode for reduced

current consumption or fixed-frequency FPWM mode

to eliminate frequency variation to minimize EMI. Fixed

frequency FPWM mode is extremely useful for power

supplies designed for RF transceivers where tight emis-

sion control is necessary. Protection features include

cycle-by-cycle current limit, overvoltage protection, and

thermal shutdown with automatic recovery. Additional

features include a power-good monitor to ease power-

supply sequencing and a 180N out-of-phase clock output

relative to the internal oscillator at SYNCOUT to create

cascaded power supplies with multiple devices.

Wide Input Voltage Range

The devices include two separate supply inputs (SUP and

SUPSW) specified for a wide 3.5V to 36V input voltage

range. VSUP provides power to the device and VSUPSW

provides power to the internal switch. When the device

is operating with a 3.5V input supply, conditions such as

cold crank can cause the voltage at SUP and SUPSW to

drop below the programmed output voltage. Under such

conditions, the device operates in a high duty-cycle mode

to facilitate minimum dropout from input to output.

Maximum Duty-Cycle Operation

The devices have a maximum duty cycle of 98% (typ).

The IC monitors the off-time (time for which the low-

side FET is on) in both PWM and skip modes every

switching cycle. Once the off-time of 25ns (typ) is

detected continuously for 12μs, the low-side FET is

forced on for 150ns (typ) every 12μs. The input voltage

at which the devices enter dropout changes depend-

ing on the input voltage, output-voltage, switching fre-

quency, load current, and the efficiency of the design.

The input voltage at which the devices enter dropout

can be approximated as:

VSUP

=

VOUT

+

(IOUT× R ON_H)

0.98

Note: The equation above does not take into account

the efficiency and switching frequency, but is a good

first-order approximation. Use the RON_H number from

the max column in the Electrical Characteristics table.

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