Single Quick-PWM Step-Down

Controller with Dynamic REFIN

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9

Pin Description

PIN

NAME

FUNCTION

1

Supply Voltage Input for the DL Gate Driver. Connect to the system supply voltage (+4.5V to

2

DL

and REFOK lockout conditions.

3

N.C.

Not Connected

4

LX

Inductor Connection. Connect LX to the switched side of the inductor as shown in Figure 1.

5

DH

High-Side Gate Driver. DH swings from LX to BST. The MAX17024 pulls DH low whenever the

controller is disabled.

6

BST

Boost Flying-Capacitor Connection. Connect to an external 0.1µF 6V capacitor as shown in Figure 1.

The MAX17024 contains an internal boost switch/diode (see Figure 2).

7

TON

Switching Frequency-Setting Input. An external resistor between the input power source and TON

drops below 10µA, the MAX17024 shuts down and enters a high-impedance state. TON is high

impedance in shutdown.

8

FB

Feedback Voltage-Sense Connection. Connect directly to the positive terminal of the output

capacitors for output voltages less than 2V as shown in Figure 1. For fixed-output voltages greater

than 2V, connect REFIN to REF and use a resistive divider to set the output voltage (Figure 4). FB

senses the output voltage to determine the on-time for the high-side switching MOSFET.

9

CS

Current-Sense Input Pin. Connect to low-side MOSFET current-sense resistor. The current-limit

threshold is 20mV (typ).

10

REFIN

MAX17024 using the resistor-divider connected between REF and GND. The MAX17024 includes

an internal window comparator to detect REFIN voltage transitions, allowing the controller to blank

PGOOD and the fault protection.

11

REF

2V Reference Voltage. Bypass to analog ground using a 470pF to 1nF ceramic capacitor. The

reference can source up to 50µA for external loads.

12

EN

into its 2µA shutdown state. When disabled, the MAX17024 slowly ramps down the target/output

voltage to ground and after the target voltage reaches 0.1V, the controller forces both DH and DL

low and enters the low-power shutdown state. Toggle EN to clear the fault-protection latch.

13

14

PGOOD

Open-Drain Power-Good Output. PGOOD is low when the output voltage is more than 200mV (typ)

soft-start circuit has terminated, PGOOD becomes high impedance if the output is in regulation.

PGOOD is blanked—forced high-impedance state—when a dynamic REFIN transition is detected.

EP

(15)

GND

Ground/Exposed Pad. Internally connected to the controller’s ground plane and substrate.

Connect directly to ground.

TC

R

k

V

V

SW

TON

TON

FB

OUT

=+

⎝⎜

⎞

⎠⎟

65

.

Ω