2.2MHz, Dual-Output Buck or Boost

Converter with POR and Power-Fail Output

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9

Typical Operating Characteristics (continued)

Pin Description

PIN

NAME

FUNCTION

1

CLKOUT

Clock Output. CLKOUT is 45° phase-shifted with respect to converter 2 (SOURCE2, Figure 3). Connect

CLKOUT (master) to the SYNC of a second MAX5072 (slave) for a four-phase converter.

2

BST2/VDD2

Buck Converter Operation—Bootstrap Flying-Capacitor Connection for Converter 2. Connect BST2/VDD2

to an external ceramic capacitor and diode according to the Standard Application Circuit (Figure 1).

Boost Converter Operation—Driver Bypass Capacitor Connection. Connect a low-ESR 0.1µF ceramic

capacitor from BST2/VDD2 to PGND (Figure 9).

3, 4

DRAIN2

Connection to Converter 2 Internal MOSFET Drain. Buck converter operation—use the MOSFET as a

high-side switch and connect DRAIN2 to the input supply. Boost converter operation—use the MOSFET

as a low-side switch and connect DRAIN2 to the inductor and diode junction (Figure 9).

5

EN2

Active-High Enable Input for Converter 2. Drive EN2 low to shut down converter 2, drive EN2 high for normal

operation. Use EN2 in conjunction with EN1 for supply sequencing. Connect to VL for always-on operation.

6

FB2

Feedback Input for Converter 2. Connect FB2 to a resistive divider between converter 2’s output and SGND

to adjust the output voltage. To set the output voltage below 0.8V, connect FB2 to a resistive voltage-divider

from BYPASS to regulator 2’s output (Figure 6). See the Setting the Output Voltage section.

7

COMP2

Compensation Connection for Converter 2. See the Compensation section to compensate converter 2’s

control loop.

8

PFO

Dying Gasp Comparator Output. The PFO open-drain output goes low when PFI falls below the 0.78V reference.

9

SYNC

External Clock Synchronization Input. Connect SYNC to a 400kHz to 4400kHz clock to synchronize the

switching frequency with the system clock. Each converter frequency is one half the frequency applied to

SYNC. Connect SYNC to SGND when not used.

10

PFI

Dying Gasp Comparator Noninverting Input. Connect a resistor-divider from the input supply to PFI. PFI

uncommitted comparator and can be used for any protection feature such as OVP or POWER-GOOD.

100ms/div

MANUAL RESET (MR)

MAX5072 toc23

5V/div

MR

5V/div

RST

5V/div

5V/div

400ns/div

FOUR-PHASE OPERATION

(SEE FIGURE 3)

MAX5072 toc24

0V

0V

0V

SOURCE 1

(MASTER)

SOURCE 2

(MASTER)

SOURCE 1

(SLAVE)

SOURCE 2

(SLAVE)