With dual synchronized out-of-phase operation, the

MAX1875/MAX1876’s high-side MOSFETs turn-on 180°

out-of-phase. The instantaneous input current peaks of

both regulators no longer overlap, resulting in reduced

RMS ripple current and input voltage ripple. This reduces

the required input capacitor ripple-current rating, allow-

ing fewer or less expensive capacitors, and reduces

shielding requirements for EMI. The Out-of-Phase

Waveforms in the Typical Operating Characteristics

demonstrate synchronized 180° out-of-phase operation.

All MAX1875/MAX1876 functions are internally powered

from an on-chip, low-dropout 5V regulator. The maxi-

mum regulator input voltage (V+) is 23V. Bypass the

MAX1875/MAX1876 also employs an undervoltage

with a 0.1µF capacitor.

Dual 180° Out-of-Phase PWM Step-

Down Controllers with POR

8

_______________________________________________________________________________________

V+

BST1

DH1

LX1

DL1

BST2

DH2

LX2

DL2

FB1

COMP1

*IRF7811W

**OPTIONAL

FB2

COMP2

PGND

REF

GND

OSC

SYNC

CKO

ILIM1

ILIM2

EN

OFF

ON

RESET OUTPUT

CLOCK OUTPUT

RST (MAX 1876 ONLY)

MAX1875

MAX1876

0.22

µF

2

× 10µF

4

× 220µF

L1

1

µH

OUTPUT1

6V - 23V

0.1

µF

R1A

8.06k

Ω

R1B

10k

Ω

5.9k

Ω

10nF

100pF

0.22

µF

6.8nF

100pF

8.2k

Ω

R2B

10k

Ω

96.5k

Ω

140k

Ω

R2A

15k

Ω

4.7

Ω

4.7

Ω

4.7

Ω

**

**

L2

1.2

µH

4

× 220µF

2

× 10µF

OUTPUT2

0.1

µF

4.7

µF

0.1

µF

118k

Ω

D3

CMSSH-3

84.5k

Ω

D2

CMSSH-3

Figure 1. Standard Application Circuit