Datasheet

MAX1875/MAX1876
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.
Internal 5V Linear Regulator (V
L
)
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
regulator’s output (V
L
) with a 4.7µF ceramic capacitor
to PGND. The V
L
dropout voltage is typically 500mV, so
when V+ is greater than 5.5V, V
L
is typically 5V. The
MAX1875/MAX1876 also employs an undervoltage
lockout circuit that disables both regulators when V
L
falls below 4.5V. V
L
should also be bypassed to GND
with a 0.1µF capacitor.
Dual 180° Out-of-Phase PWM Step-
Down Controllers with POR
8 _______________________________________________________________________________________
V+
BST1
DH1
LX1
DL1
V
L
BST2
DH2
LX2
DL2
FB1
COMP1
*IRF7811W
**OPTIONAL
FB2
COMP2
PGND
REF
GND
OSC
SYNC
CKO
ILIM1
ILIM2EN
OFF
ON
RESET OUTPUT
CLOCK OUTPUT
V
L
RST (MAX 1876 ONLY)
MAX1875
MAX1876
C
V+
0.22µF
C
IN1
2
×
10µF
C
OUT1
4
×
220µF
N
H1*
N
L1*
L1
1µH
OUTPUT1
V
OUT
= 1.8V
V
IN
6V - 23V
C
BST1
0.1µF
R1A
8.06kΩ
R1B
10kΩ
R
COMP1
5.9kΩ
C
COMP1A
10nF
C
COMP1B
100pF
C
REF
0.22µF
C
COMP2A
6.8nF
C
COMP2B
100pF
R
COMP2
8.2kΩ
R2B
10kΩ
96.5kΩ
140kΩ
R2A
15kΩ
4.7Ω
4.7Ω
R
V+
4.7Ω
N
L2*
**
**
N
H2*
L2
1.2µH
C
OUT2
4
×
220µF
C
IN2
2
×
10µF
OUTPUT2
V
OUT
= 2.5V
C
BST2
0.1µF
C
VL
4.7µF
0.1µF
118kΩ
D3
CMSSH-3
84.5kΩ
D2
CMSSH-3
Figure 1. Standard Application Circuit