MAX20002CATPC datasheet(12/19 Pages) MAXIM

12 / 19 page

Detailed Description

The MAX20002/MAX20003 are 2A/3A current-mode step-

down converters with integrated high-side and low-

side MOSFETs. The low-side MOSFET enables fixed-

frequency, forced-PWM operation in light-load applica-

tions. The devices operate with input voltages from 3.5V

to 36V while using only 15µA 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 devices’ 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

99% duty cycle during undervoltage transients, makes the

devices ideal for automotive applications.

In light-load applications, a logic input (FSYNC) allows

the devices to operate either in skip mode for reduced

current consumption, or fixed-frequency, forced-PWM

mode to eliminate frequency variation and help minimize

EMI. Protection features include cycle-by-cycle current

limit, and thermal shutdown with automatic recovery.

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 the SUP and SUPSW

pins to drop below the programmed output voltage. Under

such conditions, the devices operate 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 switch-

ing cycle. Once the off time of 100ns (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 depending on the input

voltage, output voltage, switching frequency, load current,

and the efficiency of the design.

The input voltage at which the devices enter dropout can

be approximated as:

OUT

ON_H

SUP

)

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.

Linear Regulator Output (BIAS)

The devices include a 5V linear regulator (VBIAS) that

provides power to the internal circuit blocks. Connect a

2.2µF ceramic capacitor from BIAS to AGND.

Power-Good Output (PGOOD)

The devices feature an open-drain power-good output

(PGOOD). PGOOD asserts when VOUT rises above 95%

of its regulation voltage. PGOOD deasserts when VOUT

drops below 92.5% of its regulation voltage. Connect

PGOOD to BIAS with a 10kΩ resistor.

Synchronization Input (FSYNC)

FSYNC is a logic-level input useful for operating-mode

selection and frequency control. Connecting FSYNC to

BIAS or to an external clock enables fixed-frequency,

forced-PWM operation. Connecting FSYNC to AGND

enables skip-mode operation.

The external clock frequency at FSYNC can be higher

or lower than the internal clock by 20%. If the external

clock frequency is greater than 120% of the internal clock,

contact the factory applications team to verify the design.

The devices synchronize to the external clock in two

cycles. When the external clock signal at FSYNC is

absent for more than two clock cycles, the devices use

the internal clock.

System Enable (EN)

An enable control input (EN) activates the devices from

their low-power shutdown mode. EN is compatible with

inputs from automotive battery level down to 3.5V. The

high-voltage compatibility allows EN to be connected

to SUP, KEY/KL30, or the inhibit pin (INH) of a CAN

transceiver.

EN turns on the internal regulator. Once VBIAS is above

the internal lockout threshold, VUVBIAS = 3.15V (typ),

the converter activates and the output voltage ramps up

within 8ms.

A logic-low at EN shuts down the device. During shut-

down, the internal linear regulator and gate drivers turn

off. Shutdown is the lowest power state and reduces the

quiescent current to 5µA (typ). Drive EN high to bring the

devices out of shutdown.

www.maximintegrated.com

Maxim Integrated │ 12

MAX20002/MAX20003

36V, 220kHz to 2.2MHz, 2A/3A Fully

Integrated Step-Down Converters

with 15μA Operating Current

MAX20002CATPC 数据表(PDF) 12 Page - Maxim Integrated Products

MAX20002CATPC 数据表(HTML) 12 Page - Maxim Integrated Products

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

数据表下载