Single Quick-PWM Step-Down

Controller with Dynamic REFIN

______________________________________________________________________________________

11

DYNAMIC OUTPUT

TRANSITION DETECTION

BST

LX

ONE-SHOT

TRIG

Q

ON-TIME

COMPUTE

OUT

TON

ERROR

AMPLIFIER

EA + 0.3V

ONE-SHOT

TRIG

Q

ZERO CROSSING

FB

EA

PGOOD

EN

PGOOD

AND FAULT

PROTECTION

EA - 0.2V

BLANK

REFIN

VALLEY CURRENT LIMIT

GND

CS

S

R

Q

S

R

Q

DH

IN

SOFT-

START/STOP

DL

2V

REF

INTEGRATOR

(CCV)

REF

MAX17024

Figure 2. MAX17024 Functional Block Diagram

The MAX17024 requires an external 5V bias supply in

addition to the battery. Typically, this 5V bias supply is

the notebook’s main 95% efficient 5V system supply.

Keeping the bias supply external to the IC improves

efficiency and eliminates the cost associated with the

5V linear regulator that would otherwise be needed to

supply the PWM circuit and gate drivers. If stand-alone

capability is needed, the 5V supply can be generated

with an external linear regulator, such as the MAX1615.

The 5V bias supply powers both the PWM controller

and internal gate drive, so the maximum current drawn

is determined by:

The MAX17024 includes a 20

Free-Running Constant-On-Time PWM

Controller with Input Feed-Forward

The Quick-PWM control architecture is a pseudo-fixed-

frequency, constant on-time, current-mode regulator

with voltage feed-forward (Figure 2). This architecture

relies on the output filter capacitor’s ESR to act as a cur-

rent-sense resistor, so the output ripple voltage provides

the PWM ramp signal. The control algorithm is simple:

the high-side switch on-time is determined solely by a