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MAX17682
4.5V to 42V Input, Ultra-Small, High-Efficiency,
Iso-Buck DC-DC Converter
General Description
The MAX17682 is a high-voltage, high-efficiency, iso-buck
DC-DC converter designed to provide isolated power up
to 10W. The device operates over a wide 4.5V to 42V
input voltage range and uses primary-side feedback
to regulate the output voltage. It delivers primary peak
current up to 3.7A and regulates primary output voltage to
within ±1.2% over -40°C to +125°C.
The device features peak-current-mode control with
pulse-width modulation (PWM) scheme. The low-resis-
tance, on-chip MOSFETs ensure high efficiency at full
load and simplify the layout.
A programmable soft-start feature allows users to reduce
input inrush current. The device also incorporates an
output enable/undervoltage lockout pin (EN/UVLO) that
allows the user to turn on the part at the desired input-
voltage level. An open-drain RESETB pin provides a
delayed power-good signal to the system upon achieving
successful regulation of the primary output voltage.
The device operates over the -40°C to +125°C industrial
temperature range and is available in a compact 20-pin
(4mm x 4mm) TQFN package. Simulation models are
available.
Benefits and Features
●
Eliminates External Components and Reduces Total
Cost
•
Synchronous Primary Operation for High Efficiency
and Reduced Cost
• All-Ceramic Capacitors, Ultra-Compact Layout
●
Reduces Number of DC-DC Regulators to Stock
• Wide 4.5V to 42V Input Voltage Range
• 0.9V to 92% V
IN
Primary Output Voltage
• Delivers up to 3.7A Peak Current
• 100kHz to 500kHz Adjustable Frequency with
External Synchronization
• Available in a 20-Pin, 4mm x 4mm TQFN Package
●
Reduces Power Dissipation
•
Peak Efficiency > 90%
•
Shutdown Current = 2.8μA (typ)
●
Operates Reliably in Adverse Industrial Environments
• Hiccup-Mode Current Limit, Sink Current Limit, and
Auto-Retry Startup
• Programmable EN/UVLO Threshold
• Adjustable Soft-Start
• High Industrial -40°C to +125°C Ambient Operating
Temperature Range
• -40°C to +150°C Junction Temperature Range
Applications
●
●
●
●
Industrial Process Control
Communication Hub in Smart meters
Isolated Power Supplies in Medical Equipment
Floating Power Supply Generation
Ordering Information
appears at end of data sheet.
19-8639; Rev 1; 4/18
MAX17682
4.5V to 42V Input, Ultra-Small, High-Efficiency,
Iso-Buck DC-DC Converter
Absolute Maximum Ratings
V
IN
to PGND .........................................................-0.3V to +48V
EN/UVLO to PGND ...............................................-0.3V to +42V
LX to PGND................................................-0.3V to (V
IN
+ 0.3V)
BST to PGND .................................................-0.3V to (LX + 5V)
BST to LX .............................................................-0.3V to +6.5V
BST to V
CC
...........................................................-0.3V to +42V
V
CC
, SYNC,
RESETB
, COMP, SS, RT to SGND
..........................................................................-0.3V to +6.5V
FB to SGND .........................................................-0.3V to +1.5V
SGND to PGND....................................................-0.3V to +0.3V
LX Total RMS Current ...........................................................±4A
Output Short-Circuit Duration ....................................Continuous
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................ -65°C to +160°C
Lead Temperature (soldering, 10s) ................................. +300°C
Soldering Temperature (reflow) .......................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability. Junction temperature greater than +125°C degrades operating lifetimes.
Package Thermal Characteristics
(Note 1)
20 TQFN
Continuous Power Dissipation (T
A
= +70°C) (derate
30.3mW/°C above +70°C) (multilayer board) .........2424.2mW
Junction-to-Ambient Thermal Resistance (θ
JA
) ..........33°C/W
Junction-to-Case Thermal Resistance (θ
JC
) .................2°C/W
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to
www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(V
IN
= V
EN
= 24V, R
RT
= 82.5kΩ (250kHz), V
SGND
= V
PGND
= V
SYNC
= 0V, C
VCC
= 2.2μF, V
FB
= 1V, V
BST to LX
= 5V, LX = RESETB
= SS = COMP = unconnected. T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C. All voltages are
referenced to SGND, unless otherwise noted.) (Note 2)
PARAMETER
INPUT SUPPLY (VIN)
Input Voltage Range
Input Quiescent Current
Input Quiescent Current
Input Switching Current
ENABLE/UVLO (EN/UVLO)
V
ENR
EN Threshold
EN Input Leakage Current
LDO
V
CC
Output Voltage Range
V
CC
Current Limit
V
CC
Dropout
V
CC
UVLO
V
CC
I
VCC-MAX
V
CC-DO
V
CC-UVR
V
CC-UVF
6V < V
IN
< 42V, I
VCC
= 1mA
1mA < I
VCC
< 25mA
V
CC
= 4.3V, V
IN
= 6V
V
IN
= 4.5V, I
VCC
= 20mA
V
CC
rising
V
CC
falling
4.75
26.5
4.2
4.05
3.65
4.2
3.8
4.3
3.9
5
55
5.25
100
V
mA
V
V
V
ENF
V
EN-TRUESD
I
EN
V
EN
rising
V
EN
falling
V
EN
falling, true shutdown
V
EN
= V
IN
= 60V, T
A
= +25˚C
-50
1.19
1.068
1.215
1.09
0.8
0
+50
nA
1.26
1.131
V
V
IN
I
IN-SH
I
Q
I
SW
V
FB
= 0.8V
V
EN
= 0V, shutdown mode
4.5
2.8
1.16
6
42
4.5
1.8
V
µA
mA
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
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Maxim Integrated
│
2
MAX17682
4.5V to 42V Input, Ultra-Small, High-Efficiency,
Iso-Buck DC-DC Converter
Electrical Characteristics (continued)
(V
IN
= V
EN
= 24V, R
RT
= 82.5kΩ (250kHz), V
SGND
= V
PGND
= V
SYNC
= 0V, C
VCC
= 2.2μF, V
FB
= 1V, V
BST to LX
= 5V, LX = RESETB
= SS = COMP = unconnected. T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C. All voltages are
referenced to SGND, unless otherwise noted.) (Note 2)
PARAMETER
POWER MOSFETs
High-Side NMOS On-Resistance
Low-Side NMOS On-Resistance
LX Leakage Current
SOFT-START (SS)
Charging Current
FEEDBACK (FB)
FB Regulation Voltage
FB Input Bias Current
CURRENT LIMIT
Peak Current Limit Threshold
Runaway Current Limit Threshold
Valley Current Limit Threshold
RT AND SYNC
R
RT
= OPEN
R
RT
= 210kΩ
Switching Frequency
f
SW
R
RT
= 102kΩ
R
RT
= 82.5kΩ
R
RT
= 40.2kΩ
SYNC Frequency Capture Range
SYNC Pulse Width
SYNC Threshold
Feedback Undervoltage Trip Level
to Cause Hiccup
HICCUP Timeout
Minimum On-Time
Minimum Off-Time
LX Dead Time
Number of ZX Events to Trigger
HICCUP
t
ON_MIN
t
OFF_MIN
(Note 4)
140
5
16
V
IH
V
IL
V
FB-HICF
V
SS
> 0.95V
(soft-start is done)
(Note 3)
0.56
0.58
32768
330
425
160
f
SW
set by R
RT
1.1 x
f
SW
50
2.1
0.8
0.65
250
100
200
250
500
1.4 x
f
SW
kHz
ns
V
V
Cycles
ns
ns
ns
Cycles
kHz
I
PEAK-LIMIT
I
RUNAWAY-
LIMIT
SYMBOL
R
DS-ONH
R
DS-ONL
I
LX_LKG
CONDITIONS
I
LX
= 0.3A (sourcing)
I
LX
= 0.3A (sinking)
T
A
= +25˚C, V
LX
= (V
PGND
+
1V) to (V
IN
– 1V)
V
SS
= 0.5V
MIN
TYP
165
80
MAX
325
150
+2
UNITS
mΩ
mΩ
μA
-2
I
SS
V
FB_REG
I
FB
4.7
0.89
5
0.9
5.3
0.91
+50
μA
V
nA
A
A
A
V
FB
= 1V, T
A
= +25˚C
-50
3.2
3.7
5
3.7
4.3
6.5
4.3
5
I
SINK-LIMIT
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Maxim Integrated
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3
MAX17682
4.5V to 42V Input, Ultra-Small, High-Efficiency,
Iso-Buck DC-DC Converter
Electrical Characteristics (continued)
(V
IN
= V
EN
= 24V, R
RT
= 82.5kΩ (250kHz), V
SGND
= V
PGND
= V
SYNC
= 0V, C
VCC
= 2.2μF, V
FB
= 1V, V
BST to LX
= 5V, LX = RESETB
= SS = COMP = unconnected. T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C. All voltages are
referenced to SGND, unless otherwise noted.) (Note 2)
PARAMETER
RESETB
RESETB Output Level Low
RESETB Output Leakage
Current High
FB Threshold for RESETB
Assertion
FB Threshold for RESETB
Deassertion
RESETB Delay After FB Reaches
95% Regulation
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
Temperature rising
165
10
°C
°C
V
FB-OKF
V
FB-OKR
I
RESETB
= 10mA
T
A
= T
J
= 25°C
V
FB
falling
V
FB
rising
V
FB
rising
90.5
93.8
92
95
1024
0.4
0.1
94.6
97.8
V
μA
%V
FB-
REG
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
%V
FB-
REG
Cycles
Note 2:
All limits are 100% tested at +25°C. Limits over the operating temperature range and relevant supply voltage range are
guaranteed by design and characterization.
Note 3:
See the
Overcurrent Protection/Hiccup Mode
section for more details.
Note 4:
Guaranteed by design, not production tested.
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Maxim Integrated
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4
MAX17682
4.5V to 42V Input, Ultra-Small, High-Efficiency,
Iso-Buck DC-DC Converter
Typical Operating Characteristics
(V
IN
= 24V, V
SGND
= V
PGND
= 0V, C
VIN
= 2.2µF, C
VCC
= 2.2μF, V
EN
= 1.5V, C
SS
= 15000pF, V
FB
= 0.98 x V
OUT
, RESETB = unconnected,
T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C. All voltages are referenced to SGND, unless
otherwise noted.)
LOAD TRANSIENT RESPONSE,
(LOAD CURRENT STEPPED
FROM 75mA to 375mA)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
EFFICIENCY vs. LOAD CURRENT
toc01
toc02
V
IN
= 16V
V
IN
= 24V
V
IN
= 36V
V
OUT
(AC)
500mV/div
I
OUT
200mA/div
400µs/div
100
200
300
400
500
600
700
800
LOAD CURRENT (mA)
LOAD TRANSIENT RESPONSE
(LOAD CURRENT STEPPED
FROM 375mA to 700mA)
toc03
FULL-LOAD SWITCHING WAVEFORMS
toc04
V
OUT
(AC)
500mV/div
LX
V
OUT
(AC)
I
PRI
20V/div
200mV/div
2A/div
I
OUT
400µs/div
500mA/div
I
SEC
2µs/div
2A/div
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Analogue and Mixed Signal
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