Detailed Description

The MAX17245 is a 3.5A current-mode, step-down con-

verter 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 device operates with input voltages

from 3.5V to 36V, while using only 28µA 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 3.3V/5V

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 this device ideal for

many applications.

Under light-load applications, the FSYNC logic input

allows the device to either operate in PFM mode for

reduced current consumption or fixed-frequency PWM

mode to eliminate frequency variation to minimize EMI.

Fixed-frequency PWM mode is extremely useful for power

supplies designed for RF transceivers where tight emission

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 180° 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 device includes two separate supply inputs (SUP and

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

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 operate in a high duty-cycle mode to

facilitate minimum dropout from input to output.

In applications where the input voltage exceeds 25V,

output is ≤ 5V, operating frequency is ≥ 1.8MHz and the

IC is selected to be in PWM mode by either forcing the

FSYNC pin high, or using an external clock, pulse skipping

is observed on the LX pin. This happens due to insufficient

= 220pF to reduce ringing on the LX pin (see the Typical

Application Circuit).

Linear Regulator Output (BIAS)

The MAX17245 includes a 5V linear regulator (BIAS) that

provides power to the internal circuit blocks. Connect a

1µF ceramic capacitor from BIAS to AGND.

PIN

NAME

FUNCTION

TQFN

TSSOP

9

10

EN

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

Drive EN high to enable the device.

10

11

SUP

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

PGND with a 4.7µF 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).

11

12

SUPSW

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

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

12, 13

13, 14

LX

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

14

15

PGND

Power Ground

15

16

PGOOD

—

—

EP

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.

Pin Descriptions (continued)

www.maximintegrated.com

Maxim Integrated │ 9

MAX17245

3.5V–36V, 3.5A, Synchronous Buck Converter With

28μA Quiescent Current and Reduced EMI