MAX618 データシートの表示（PDF） - Maxim Integrated

部品番号

コンポーネント説明

メーカー

MAX618

28V Internal Switch, Step-Up DC-DC Converter

Maxim Integrated 

MAX618

28V Internal Switch, Step-Up DC-DC Converter

and the MAX618’s package power-dissipation limit. See

the Maximum Output Current section for details.

In Idle Mode, the MAX618 improves light-load

efficiency by reducing inductor current and skipping cycles

to reduce the losses in the internal switch, diode, and

inductor. In this mode, a switching cycle initiates only

when the error comparator senses that the output voltage

is about to drop out of regulation. When this occurs, the

NMOS switch turns on and remains on until the inductor

current exceeds the nominal 350mA Idle Mode current

limit.

Refer to Table 1 for an estimate of load currents at which

the MAX618 transitions between PWM and Idle Mode.

Compensation Scheme

Although the higher loop gain of voltage-controlled

architectures tends to provide tighter load regulation,

current-controlled architectures are generally easier to

compensate over wide input and output voltage ranges.

The MAX618 uses both control schemes in parallel:

the dominant, low-frequency components of the error

signal are tightly regulated with a voltage-control loop,

while a current-control loop improves stability at higher

frequencies. Compensation is achieved through the

selection of the output capacitor (COUT), the integrator

capacitor (CCOMP), and the pole capacitor (CP) from

FB to GND. CP cancels the zero formed by COUT and

its ESR. Refer to the Capacitor Selection section for

guidance on selecting these capacitors.

VL Low-Dropout Regulator

The MAX618 contains a 3.1V low-dropout linear regulator

to power internal circuitry. The regulator’s input is IN and

its output is VL. The IN to VL dropout voltage is 100mV,

so that when IN is less than 3.2V, VL is typically 100mV

below IN. The MAX618 still operates when the LDO is in

dropout, as long as VL remains above the 2.7V undervolt-

age lockout. Bypass VL with a 4.7μF ceramic capacitor

placed as close to the VL and GND pins as possible.

VL can be overdriven by an external supply between

2.7V and 5.5V. In systems with +3.3V or +5V logic power

supplies available, improve efficiency by powering VL and

VIN directly from the logic supply as shown in Figure 3.

www.maximintegrated.com

Maxim Integrated │  7

Share Link: