MAX17681
4.5V to 42V Input, High-Efficiency,
Iso-Buck DC-DC Converter
General Description
Benefits and Features
● Reduces External Components and Total Cost
The MAX17681/MAX17681A is a high-voltage, high-
efficiency, iso-buck DC-DC converter designed to provide
isolated power up to 5W. The device operates over a
wide 4.5V to 42V input and uses primary-side feedback
to regulate the output voltage.
• No Optocoupler
• Synchronous Primary Operation
• All-Ceramic Capacitors, Compact Layout
● Reduces Number of DC-DC Regulators to Stock
The MAX17681/MAX17681A uses peak-current-mode
control. The low-resistance, on-chip MOSFETs ensure
high efficiency at full load while simplifying the PCB layout.
• Wide 4.5V to 42V Input
• 0.9V to 0.96 x V Primary Output Voltage
IN
• Delivers Up to 5W Output Power
The MAX17681/MAX17681A devices generate a well
regulated primary side voltage which is then scaled by a
suitable transformer turns ratio to derive isolated secondary
output rails. While both MAX17681 and MAX17681A
support primary side overcurrent protection, the
MAX17681A is an enhanced design that supports robust
secondary-side overcurrent protection as well.
● Reduces Power Dissipation
• Peak Efficiency > 90%
• 0.9μA (typ) Shutdown Current
● Operates Reliably in Adverse Industrial Environments
• Peak and Sink Current-Limit Protection
• ±1.7% Feedback Accuracy
• Programmable EN/UVLO Threshold
• Adjustable Soft-Start
• Overtemperature Protection
The MAX17681/MAX17681A is available in a compact
10-pin (3mm x 2mm) TDFN package. Simulation models
are available.
• -40°C to +125°C Operation
● Short-Circuit Protection
Applications
● Isolated Fieldbus Interfaces
● PLC I/O Modules
● Smart Meters
• MAX17681A Supports Robust Secondary-Side
Short-Circuit Protection
• MAX17681A Is Recommended for All New Designs
● Isolated Power Supplies in Medical Equipment
● Floating Power Supply Generation
Ordering Information appears at end of data sheet.
Application Circuit
T1
1:2.4
V
OUT
D1
24V, 100mA
V
IN
LX
V
IN
17V TO 32V
C1
1µF
R4
49.9Ω
PGND
EN/UVLO
C7
2.2µF
N
N
SEC
PRI
Z1
V
CC
GND
C3
MAX17681
MAX17681A
1µF
C2
10uF
R1
105kΩ
SS
FB
C4
33nF
R2
10kΩ
C8
1nF
COMP
RESET
R3
4.75kΩ
C6
680pF
C5
33nF
19-7053; Rev 4; 3/18