MAX17633AATP [MAXIM]
4.5V to 36V, 3.5A, High Efficiency, Synchronous Step-Down, DC-DC Converter;
| 型号： | MAX17633AATP |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 4.5V to 36V, 3.5A, High Efficiency, Synchronous Step-Down, DC-DC Converter |
| 文件： | 总23页 (文件大小：1472K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
General Description
Benefits and Features
● Reduces External Components and Total Cost
• No Schottky - Synchronous Operation
• Internal Compensation Components
The Himalaya series of voltage regulator ICs, power mod-
ules, and chargers enable cooler, smaller, and simpler
power supply solutions. The MAX17633 is a high-effi-
ciency, high-voltage, Himalaya synchronous step-down
DC-DC converter with integrated MOSFETs operating
over an input voltage range of 4.5V to 36V. It can deliver
up to 3.5A current. The MAX17633 is available in three
variants MAX17633A, MAX17633B, and MAX17633C.
The MAX17633A and MAX17633B are the fixed 3.3V and
fixed 5V output voltage parts, respectively. MAX17633C
is an adjustable output voltage (from 0.9V up to 90% of
• All-Ceramic Capacitors, Compact Layout
● Reduces Number of DC-DC Regulators to Stock
• Wide 4.5V to 36V Input
• Adjustable Output Range from 0.9V up to 90% of V
• Delivers up to 3.5A Over the Temperature Range
• 400kHz to 2.2MHz Adjustable Frequency with
External Clock Synchronization
IN
• Available in a 20-Pin, 4mm × 4mm TQFN Package
V ) part. Built-in compensation across the output voltage
IN
● Reduces Power Dissipation
• Peak Efficiency > 93%
range eliminates the need for external components.
The MAX17633 features peak-current-mode control archi-
tecture. The device can be operated in forced pulse-width
modulation (PWM), pulse-frequency modulation (PFM),
or discontinuous-conduction mode (DCM) to enable high
efficiency under full-load and light-load conditions.
• PFM and DCM Modes Enable Enhanced Light-
Load Efficiency
• Auxiliary Bootstrap Supply (EXTVCC) for Improved
Efficiency
• 2.8μA Shutdown Current
The feedback-voltage-regulation accuracy over -40°C
to +125°C for the MAX17633A, MAX17633B, and
MAX17633C is ±1.3%. Simulation models are available.
● Operates Reliably in Adverse Industrial Environments
• Hiccup-Mode Overload Protection
• Adjustable and Monotonic Startup with Prebiased
Output Voltage
Applications
• Built-in Output-Voltage Monitoring with RESET
• Programmable EN/UVLO Threshold
• Overtemperature Protection
● Industrial Control Power Supplies
● General-Purpose Point-of-Load
● Distributed Supply Regulation
● Base-Station Power Supplies
● Wall Transformer Regulation
● High-Voltage Single-Board systems
• CISPR 22 Class B Compliant
• Wide -40°C to +125°C Ambient Operating Temper-
ature Range / -40°C to +150°C Junction Tempera-
ture Range
Ordering Information appears at end of data sheet.
Typical Application Circuit
V
IN
6.5V TO 36V
C1
2 x 2.2µF
RT
IN
EN/UVLO
BST
LX
MODE/SYNC
C5
0.1µF
L1
V
OUT
INTVCC
6.8µH
C3
2.2µF
C4
2 x 22µF
5V,3.5A
MAX17633B
SGND
EXTVCC
SS
FB
C2
EP
5600pF
PGND
RESET
19-100305; Rev 2; 7/20
MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Absolute Maximum Ratings
IN to PGND ...........................................................-0.3V to +40V
PGND to SGND....................................................-0.3V to +0.3V
LX Total RMS Current .............................................................4A
Output Short-Circuit Duration....................................Continuous
Continuous Power Dissipation (Multilayer Board)
EN/UVLO to SGND....................................-0.3V to (V + 0.3V)
LX to PGND................................................-0.3V to (V + 0.3V)
IN
IN
EXTVCC to SGND ...............................................-5.5V to +6.5V
BST to PGND.....................................................-0.3V to +46.5V
BST to LX.............................................................-0.3V to +6.5V
BST to INTVCC.....................................................-0.3V to +40V
FB to SGND (MAX17633A & MAX17633B).........-5.5V to +6.5V
FB to SGND (MAX17633C) .................................-0.3V to +6.5V
SS, MODE/SYNC, RESET, INTVCC,
(T = +70°C, derate 30.3mW/°C above +70°C.)....2424.2mW
A
Operating Temperature Range (Note1)...............-40°C to 125°C
Junction Temperature....................................... -40°C to +150°C
Storage Temperature Range............................ -65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow).......................................+260°C
RT to SGND .....................................................-0.3V to +6.5V
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.
Package Information
PACKAGE TYPE: 20-Pin TQFN
Package Code
T2044+4C
21-100172
90-0409
Outline Number
Land Pattern Number
THERMAL RESISTANCE, FOUR-LAYER BOARD (Note 2)
Junction to Ambient (θ
)
26°C/W
2°C/W
JA
Junction to Case (θ
)
JC
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Note 1: Junction temperature greater than +125°C degrades operating lifetimes.
Note 2: Package thermal resistances were obtained using the MAX17633 Evaluation Kit with no airflow.
Maxim Integrated
│ 2
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Electrical Characteristics
(V = V
= 24V, R = unconnected (f
= 500 kHz), C
= 2.2μF, V
= V
= V
= V = 0V;
EXTVCC
IN
EN/UVLO
RT
SW
INTVCC
SGND
PGND
MODE/SYNC
V
= 3.67V (MAX17633A), V = 5.5V (MAX17633B), V
= 1V (MAX17633C), LX = SS = RESET = OPEN, V
to V = 5V,
FB
FB
FB
BST
LX
T = -40°C to 125°C, unless otherwise noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise
A
A
noted.) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Input-Voltage Range
V
4.5
36
V
IN
Input-Shutdown Current
I
V
= 0V (Shutdown mode)
2.8
96
4.5
μA
IN_SH
EN/UVLO
MODE/SYNC = OPEN, V
= 5V
EXTVCC
I
μA
R
V
= 40.2kΩ, MODE/SYNC = OPEN,
Q_PFM
RT
106
= 5V
Input-Quiescent Current
EXTVCC
I
DCM Mode, V = 0.1V
LX
1.2
11
1.8
Q_DCM
mA
I
Normal switching mode; V
= 5V
EXTVCC
Q_PWM
EN/UVLO
V
V
V
V
rising
falling
1.19
1.068
-50
1.215
1.09
0
1.26
1.131
+50
ENR
EN/UVLO
EN/UVLO
EN/UVLO
EN Threshold
V
V
ENF
EN Input-Leakage Current
I
= 0V, T = +25ºC
A
nA
EN
INTVCC
1mA ≤ I
≤ 25mA
4.75
4.75
30
5
5
5.25
5.25
INTVCC Output-Voltage
Range
INTVCC
V
V
INTVCC
6V ≤ V ≤ 36V, I
= 1mA
IN
INTVCC
INTVCC Current Limit
INTVCC Dropout
I
V
V
V
V
= 4.5V, V = 7.5V
mA
V
INTVCC_MAX
INTCC
IN
V
= 4.5V, I = 10mA
INTVCC
0.3
4.3
3.9
INTCC_DO
IN
V
rising
4.05
3.65
4.2
3.8
INTVCC Undervoltage
Lockout
INTVCC_UVR
INTVCC
INTVCC
V
V
falling
INTVCC_UVF
EXTVCC
V
V
rising
falling
4.56
4.3
4.7
4.84
4.6
EXTVCC Switchover
Threshold
EXTVCC
V
4.43
EXTVCC
POWER MOSFET
High-Side nMOS
On-Resistance
R
I
I
= 0.3A, sourcing
= 0.3A, sinking
65
40
125
80
3
mΩ
mΩ
μA
DS_ONH
LX
LX
Low-Side nMOS
On-Resistance
R
DS_ONL
LX_LKG
V
= (V
+ 1)V to (V - 1)V,
LX
PGND IN
LX Leakage Current
I
-2
T = +25°C
A
Maxim Integrated
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Electrical Characteristics (continued)
(V = V
= 24V, R = unconnected (f
= 500 kHz), C
= 2.2μF, V
= V
= V
= V = 0V;
EXTVCC
IN
EN/UVLO
RT
SW
INTVCC
SGND
PGND
MODE/SYNC
V
= 3.67V (MAX17633A), V = 5.5V (MAX17633B), V
= 1V (MAX17633C), LX = SS = RESET = OPEN, V
to V = 5V,
FB
FB
FB
BST
LX
T = -40°C to 125°C, unless otherwise noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise
A
A
noted.) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SS
Charging Current
I
4.7
5
5.3
μA
SS
FB
MODE/SYNC = SGND or MODE/SYNC =
INTVCC (MAX17633A)
3.256
4.94
3.3
5
3.344
5.06
MODE/SYNC = SGND or MODE/SYNC =
INTVCC (MAX17633B)
MODE/SYNC = SGND or MODE/SYNC =
INTVCC (MAX17633C)
FB Regulation Voltage
V
V
FB_REG
0.888
0.9
0.912
MODE/SYNC = OPEN (MAX17633A)
MODE/SYNC = OPEN (MAX17633B)
MODE/SYNC = OPEN (MAX17633C)
For MAX17633A
3.256
4.94
3.36
5.09
0.915
33
3.44
5.21
0.888
0.938
μA
FB Input-Bias Current
MODE/SYNC
I
For MAX17633B
33
FB
For MAX17633C, T = +25°C
A
-50
+50
nA
V
MODE/SYNC = INTVCC (DCM Mode)
MODE/SYNC = OPEN (PFM Mode)
MODE/SYNC = SGND (PWM Mode)
V
- 0.65
M_DCM
IN_VCC
V
MODE Threshold
V
/2
V
M_PFM
IN_VCC
V
0.75
M_PWM
SYNC Frequency-Capture
Range
f
f
set by R
1.1 × f
1.4 × f
SW
kHz
ns
SYNC
SW
RT
SW
SYNC Pulse Width
SYNC Threshold
CURRENT LIMIT
50
V
2.1
IH
V
V
0.8
6.2
IL
Peak Current-Limit
Threshold
I
4.6
5.4
6.4
1.2
A
A
A
PEAK_LIMIT
Runaway Current-Limit
Threshold
I
5.35
7.35
RUNAWAY_LIMIT
PFM Current-Limit
Threshold
I
MODE/SYNC = OPEN
PFM
MODE/SYNC = OPEN or MODE/SYNC =
INTVCC
-0.28
0
+0.28
Valley Current-Limit
Threshold
I
A
VALLEY_LIMIT
MODE/SYNC = GND
2.5
Maxim Integrated
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Electrical Characteristics (continued)
(V = V
= 24V, R = unconnected (f
= 500 kHz), C
= 2.2μF, V
= V
= V
= V = 0V;
EXTVCC
IN
EN/UVLO
RT
SW
INTVCC
SGND
PGND
MODE/SYNC
V
= 3.67V (MAX17633A), V = 5.5V (MAX17633B), V
= 1V (MAX17633C), LX = SS = RESET = OPEN, V
to V = 5V,
FB
FB
FB
BST
LX
T = -40°C to 125°C, unless otherwise noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise
A
A
noted.) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
kHz
V
RT
R
R
R
R
= 50.8kΩ
= 40.2kΩ
= OPEN
= 8.06kΩ
380
475
400
500
420
525
RT
RT
RT
RT
Switching Frequency
f
SW
460
500
540
1950
2.03
3.07
0.55
2200
2.13
3.22
0.58
32768
52
2450
2.22
3.37
0.605
MAX17633A
MAX17633B
MAX17633C
(Note 4)
V
V
FB_HICF
V
Hiccup Threshold
FB
FB_HICF
HICCUP Timeout
Minimum On-Time
Minimum Off-Time
LX Dead TIme
Cycles
ns
t
80
ON(MIN)
t
140
160
ns
OFF(MIN)
LX
5
ns
DT
RESET
RESET Output-Level Low
V
400
100
mV
nA
I
= 10mA
RESETL
RESET
RESETOutput-Leakage
Current
I
-100
93.8
90.5
T = T = 25ºC, V
= 5.5V
RESETLKG
A
J
RESET
FB Threshold for RESET
Deassertion
V
V
rising
95
92
97.8
94.6
%
%
FB_OKR
FB
FB
FB Threshold for RESET
Assertion
V
V
falling
FB_OKF
RESET Delay after FB
Reaches 95% Regulation
1024
Cycles
THERMAL SHUTDOWN
Thermal-Shutdown
Threshold
Temperature rising
165
10
°C
°C
Thermal-Shutdown
Hysteresis
Note 3: Electrical specifications are production tested at T = +25ºC. Specifications over the entire operating temperature range are
A
guaranteed by design and characterization.
Note 4: See the Overcurrent Protection/Hiccup Mode section for more details
Maxim Integrated
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Typical Operating Characteristics
(V
= V = 24V, V
= V
= 0V, C
= 2.2μF, C
= 0.1μF, C = 5600pF, T = -40°C to +125°C, unless otherwise
EN/UVLO
IN
SGND
PGND
INTVCC
BST SS A
noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
A
MAX17633A
EFFICIENCY vs. LOAD CURRENT
FIGURE 5 CIRCUIT
MAX17633A
EFFICIENCY vs. LOAD CURRENT
FIGURE 5 CIRCUIT
MAX17633A
EFFICIENCY vs. LOAD CURRENT
FIGURE 5 CIRCUIT
toc01
toc02
toc03
100
90
80
70
60
50
40
30
20
10
0
100
95
90
85
80
75
70
65
60
55
50
100
90
80
70
60
50
40
30
20
10
0
VIN = 12V
VIN = 24V
VIN = 36V
VIN = 4.5V
VIN = 24V
VIN = 24V
VIN = 4.5V
VIN = 36V
VIN = 4.5V
VIN = 36V
VIN = 12V
VIN = 12V
0
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE
10
10
0
100
1000
50
500
LOAD CURRENT (mA)
CONDITIONS: FIXED 3.3V OUTPUT, DCM MODE
5000
LOAD CURRENT (mA)
CONDITIONS: FIXED 3.3V OUTPUT, PFM MODE
MAX17633B
EFFICIENCY vs. LOAD CURRENT
MAX17633B
EFFICIENCY vs. LOAD CURRENT
FIGURE 6 CIRCUIT
MAX17633B
EFFICIENCY vs. LOAD CURRENT
FIGURE 6 CIRCUIT
FIGURE 6 CIRCUIT
toc05
toc06
toc04
100
95
90
85
80
75
70
65
60
55
50
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
VIN = 12V
VIN = 24V
VIN = 36V
VIN = 12V
VIN = 6.5V
VIN = 36V
VIN = 24V
VIN = 6.5V
VIN = 6.5V
VIN = 36V
VIN = 24V
VIN = 12V
0
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
CONDITIONS: FIXED 5V OUTPUT, PWM MODE
100
LOAD CURRENT (mA)
1000
50
500
5000
LOAD CURRENT (mA)
CONDITIONS: FIXED 5V OUTPUT, PFM MODE
CONDITIONS: FIXED 5V OUTPUT, DCM MODE
MAX17633A
LINE AND LOAD REGULATION
FIGURE 5 CIRCUIT
MAX17633A
LINE AND LOAD REGULATION
MAX17633A
LINE AND LOAD REGULATION
FIGURE 5 CIRCUIT
FIGURE 5 CIRCUIT
toc09
toc08
toc07
3.310
3.305
3.300
3.295
3.290
3.285
3.280
3.310
3.305
3.300
3.295
3.290
3.285
3.280
VIN = 36V
VIN = 36V
3.39
3.37
3.35
3.33
3.31
3.29
3.27
3.25
VIN = 24V
VIN = 24V
VIN = 12V
VIN = 36V
VIN = 24V
VIN = 12V
VIN = 4.5V
VIN = 4.5V
VIN = 12V
VIN = 4.5V
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
CONDITIONS: FIXED 3.3V OUTPUT, PFM MODE
0
500 1000 1500 2000 2500 3000 3500
0
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE
LOAD CURRENT (mA)
CONDITIONS: FIXED 3.3V OUTPUT, DCM MODE
Maxim Integrated
│ 6
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Typical Operating Characteristics (continued)
(V
= V = 24V, V
= V
= 0V, C
= 2.2μF, C
= 0.1μF, C = 5600pF, T = -40°C to +125°C, unless otherwise
EN/UVLO
IN
SGND
PGND
INTVCC
BST SS A
noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
A
MAX17633B
MAX17633B
MAX17633B
LINE AND LOAD REGULATION
FIGURE 6 CIRCUIT
LINE AND LOAD REGULATION
FIGURE 6 CIRCUIT
LINE AND LOAD REGULATION
FIGURE 6 CIRCUIT
toc10
toc12
toc11
5.05
5.04
5.03
5.02
5.01
5.00
4.99
4.98
4.97
4.96
4.95
5.05
5.04
5.03
5.02
5.01
5.00
4.99
4.98
5.20
5.15
5.10
5.05
5.00
4.95
VIN = 36V
VIN = 24V
VIN = 24V
VIN = 12V
VIN = 12V
VIN = 36V
VIN = 12V
VIN = 24V
VIN = 6.5V
V
IN = 6.5V
VIN = 6.5V
VIN = 36V
0
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
CONDITIONS: FIXED 5V OUTPUT, PWM MODE
0
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
CONDITIONS: FIXED 5V OUTPUT, DCM MODE
0
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
CONDITIONS: FIXED 5V OUTPUT, PFM MODE
MAX17633B
MAX17633A
MAX17633B
SOFT-START/SHUTDOWN FROM EN/UVLO
SOFT-START/SHUTDOWN FROM EN/UVLO
SOFT-START WITH PRE-BIAS OF VOLTAGE 2.5V
FIGURE 6 CIRCUIT
FIGURE 5 CIRCUIT
FIGURE 6 CIRCUIT
toc14
toc13
toc15
VEN/UVLO
V
EN/UVLO
V
5V/div
5V/div
EN/UVLO
5V/div
VOUT
V
V
2V/div
OUT
2V/div
OUT
2V/div
2A/div
I
LX
ILX
2A/div
5V/div
2A/div
5V/div
I
LX
V
V
V
RESET
RESET
RESET
5V/div
2ms/div
1ms/div
2ms/div
CONDITIONS: FIXED 5V OUTPUT, PWM MODE, 35mA LOAD
CONDITIONS: FIXED 5V OUTPUT, PWM MODE, 3.5A LOAD
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE, 3.5A LOAD
MAX17633A
STEADY STATE PERFORMANCE
MAX17633A
STEADY STATE PERFORMANCE
MAX17633A
SOFT-START WITH PRE-BIAS OF VOLTAGE 1.65V
FIGURE 5 CIRCUIT
FIGURE 5 CIRCUIT
FIGURE 5 CIRCUIT
toc18
toc17
toc16
V
LX
20V/div
20V/div
V
V
LX
EN/UVLO
5V/div
V
V
OUT (AC-
OUT (AC-
10mV/div
0.5A/div
20mV/div
V
2V/div
2A/div
OUT
COUPLED)
COUPLED)
I
LX
I
I
LX
LX
2A/div
V
RESET
5V/div
1µs/div
2µs/div
CONDITIONS: 35mA LOAD CURRENT,
FIXED 3.3V OUTPUT, DCM MODE
2ms/div
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE, 35mA LOAD
CONDITIONS: 3.5A LOAD CURRENT,
FIXED 3.3V OUTPUT, PWM MODE
Maxim Integrated
│ 7
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Typical Operating Characteristics (continued)
(V
= V = 24V, V
= V
= 0V, C
= 2.2μF, C
= 0.1μF, C = 5600pF, T = -40°C to +125°C, unless otherwise
EN/UVLO
IN
SGND
PGND
INTVCC
BST SS A
noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
A
MAX17633B
MAX17633A
MAX17633B
STEADY STATE PERFORMANCE
FIGURE 6 CIRCUIT
STEADY STATE PERFORMANCE
FIGURE 5 CIRCUIT
STEADY STATE PERFORMANCE
FIGURE 6 CIRCUIT
toc19
toc20
toc21
V
VLX
20V/div
V
LX
20V/div
LX
20V/div
V
V
OUT (AC-
OUT (AC-
VOUT (AC-
COUPLED)
20mV/div
50mV/div
100mV/div
COUPLED)
COUPLED)
I
2A/div
I
LX
LX
ILX
1A/div
2A/div
2µs/div
40µs/div
100µs/div
CONDITIONS: 3.5A LOAD CURRENT,
FIXED 5V OUTPUT, PWM MODE
CONDITIONS: 35mA LOAD CURRENT,
FIXED 3.3V OUTPUT, PFM MODE
CONDITIONS: 35mA LOAD CURRENT,
FIXED 5V OUTPUT, PFM MODE
MAX17633C
STEADY STATE PERFORMANCE
FIGURE 4 CIRCUIT
MAX17633B
STEADY STATE PERFORMANCE
FIGURE 6 CIRCUIT
MAX17633C
STEADY STATE PERFORMANCE
FIGURE 4 CIRCUIT
toc22
toc23
toc24
V
VLX
LX
20V/div
V
LX
20V/div
20V/div
VOUT (AC-
COUPLED)
V
OUT (AC-
V
10mV/div
OUT (AC-
50mV/div
20mV/div
COUPLED)
COUPLED)
I
LX
I
0.2A/div
LX
1A/div
ILX
2A/div
1µs/div
40µs/div
CONDITIONS: 3.5A LOAD CURRENT,
FIXED 5V OUTPUT, DCM MODE
1µs/div
CONDITIONS: 35mA LOAD CURRENT, 5V OUTPUT, PFM MODE
CONDITIONS: 3.5A LOAD CURRENT, 5V OUTPUT, PWM MODE
MAX17633C
STEADY STATE PERFORMANCE
FIGURE 4 CIRCUIT
MAX17633A
LOAD TRANSIENT BETWEEN 0A AND 1.75A
MAX17633A
LOAD TRANSIENT BETWEEN 1.75A AND 3.5A
FIGURE 5 CIRCUIT
FIGURE 5 CIRCUIT
toc26
toc25
toc27
V
OUT (AC-
V
OUT (AC-
V
LX
100mV/div
20V/div
100mV/div
COUPLED)
COUPLED)
V
OUT (AC-
10mV/div
COUPLED)
I
I
OUT
2A/div
OUT
1A/div
I
0.5A/div
LX
200µs/div
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE
100µs/div
1µs/div
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE
CONDITIONS: 35mA LOAD CURRENT, 5V OUTPUT, DCM MODE
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Typical Operating Characteristics (continued)
(V
= V = 24V, V
= V
= 0V, C
= 2.2μF, C
= 0.1μF, C = 5600pF, T = -40°C to +125°C, unless otherwise
EN/UVLO
IN
SGND
PGND
INTVCC
BST SS A
noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
A
MAX17633C
LOAD TRANSIENT BETWEEN 0A AND 1.75A
MAX17633A
MAX17633A
LOAD TRANSIENT BETWEEN 0.035A AND 1.75A
LOAD TRANSIENT BETWEEN 0.035A AND 1.75A
FIGURE 4 CIRCUIT
FIGURE 5 CIRCUIT
FIGURE 5 CIRCUIT
toc28
toc29
toc30
VOUT (AC-
VOUT (AC-
V
OUT (AC-
COUPLED)
100mV/div
COUPLED)
100mV/div
100mV/div
COUPLED)
IOUT
1A/div
IOUT
I
OUT
1A/div
1A/div
400µs/div
200µs/div
200µs/div
CONDITIONS: FIXED 3.3V OUTPUT, PFM MODE
CONDITIONS: FIXED 3.3V OUTPUT, DCM MODE
CONDITIONS: 5V OUTPUT, PWM MODE
MAX17633C
LOAD TRANSIENT BETWEEN 1.75A AND 3.5A
MAX17633B
LOAD TRANSIENT BETWEEN 0A AND 1.75A
MAX17633B
LOAD TRANSIENT BETWEEN 1.75A AND 3.5A
FIGURE 4 CIRCUIT
FIGURE 6 CIRCUIT
FIGURE 6 CIRCUIT
toc33
toc31
toc32
V
OUT (AC-
V
V
OUT (AC-
OUT (AC-
100mV/div
100mV/div
COUPLED)
100mV/div
COUPLED)
COUPLED)
I
I
OUT
OUT
I
2A/div
1A/div
OUT
2A/div
100µs/div
100µs/div
200µs/div
CONDITIONS: FIXED 5V OUTPUT, PWM MODE
CONDITIONS: FIXED 5V OUTPUT, PWM MODE
CONDITIONS: 5V OUTPUT, PWM MODE
MAX17633B
LOAD TRANSIENT BETWEEN 0.035A AND 1.75A
FIGURE 6 CIRCUIT
toc34
VOUT (AC-
COUPLED)
200mV/div
IOUT
1A/div
200µs/div
CONDITIONS: FIXED 5V OUTPUT, PFM MODE
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Typical Operating Characteristics (continued)
(V
= V = 24V, V
= V
= 0V, C
= 2.2μF, C
= 0.1μF, C = 5600pF, T = -40°C to +125°C, unless otherwise
EN/UVLO
IN
SGND
PGND
INTVCC
BST SS A
noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
A
MAX17633B
MAX17633B
EXTERNAL CLOCK SYNCHRONIZATION
LOAD TRANSIENT BETWEEN 0.035A AND 1.75A
FIGURE 6 CIRCUIT
FIGURE 6 CIRCUIT
toc35
toc36
V
OUT (AC-
COUPLED)
100mV/div
VSYNC
VOUT (AC-
COUPLED)
5V/div
20mV/div
VLX
20V/div
5A/div
I
OUT
1A/div
ILX
4µs/div
100µs/div
CONDITIONS: FIXED 5V OUTPUT, PWM MODE,
3.5A LOAD CURRENT, fSW = 550kHz
CONDITIONS: FIXED 5V OUTPUT, DCM MODE
MAX17633B
EXTERNAL CLOCK SYNCHRONIZATION
MAX17633A
EXTERNAL CLOCK SYNCHRONIZATION
FIGURE 6 CIRCUIT
toc37
FIGURE 5 CIRCUIT
toc38
VSYNC
VOUT (AC-
COUPLED)
5V/div
VSYNC
VOUT (AC-
COUPLED)
5V/div
20mV/div
20mV/div
VLX
20V/div
5A/div
VLX
20V/div
5A/div
ILX
ILX
4µs/div
4µs/div
CONDITIONS: FIXED 5V OUTPUT, PWM MODE,
3.5A LOAD CURRENT, fSW = 700kHz
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE,
3.5A LOAD CURRENT, fSW = 550kHz
MAX17633B
OVER LOAD PROTECTION
MAX17633A
EXTERNAL CLOCK SYNCHRONIZATION
FIGURE 6 CIRCUIT
FIGURE 5 CIRCUIT
toc39
toc40
VSYNC
VOUT (AC-
COUPLED)
VOUT
5V/div
100mV/div
20mV/div
20V/div
5A/div
VLX
ILX
2A/div
ILX
4µs/div
20ms/div
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE,
3.5A LOAD CURRENT, fSW = 700kHz
CONDITIONS: FIXED 5 OUTPUT, PWM MODE
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Typical Operating Characteristics (continued)
(V
= V = 24V, V
= V
= 0V, C
= 2.2μF, C
= 0.1μF, C = 5600pF, T = -40°C to +125°C, unless otherwise
EN/UVLO
IN
SGND
PGND
INTVCC
BST SS A
noted. Typical values are at T = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
A
MAX17633A
OVER LOAD PROTECTION
MAX17633B
CLOSED LOOP BODE PLOT
FIGURE 5 CIRCUIT
FIGURE 6 CIRCUIT
toc41
toc42
100
90
80
70
60
50
40
30
20
10
0
40
30
VOUT
100mV/div
20
10
0
-10
ILX
2A/div
-20
-30
-40
CROSSOVER
FREQUENCY = 49.1kHz
PHASE MARGIN = 67.2°
20ms/div
CONDITIONS: FIXED 3.3V OUTPUT, PWM MODE
1k
10k
100k
FREQUENCY (Hz)
CONDITIONS: 5V FIXED OUTPUT, 3.5A LOAD CURRENT, PWM MODE
MAX17633C
CLOSED LOOP BODE PLOT
MAX17633A
CLOSED LOOP BODE PLOT
FIGURE 5 CIRCUIT
FIGURE 4 CIRCUIT
toc43
toc44
100
90
80
70
60
50
40
30
20
10
0
100
40
30
40
90
80
70
60
50
40
30
30
20
20
10
10
0
0
-10
-20
-30
-40
-10
-20
-30
-40
CROSSOVER
FREQUENCY = 47.8kHz
PHASE MARGIN = 69.1°
CROSSOVER
FREQUENCY = 56.4kHz
PHASE MARGIN = 61.9°
1k
10k
100k
1k
10k
100k
FREQUENCY (Hz)
CONDITIONS: 5V ADJUSTABLEOUTPUT, 3.5A LOAD CURRENT, PWM MODE
FREQUENCY (Hz)
CONDITIONS: 3.3V FIXED OUTPUT, 3.5A LOAD CURRENT, PWM MODE
MAX17633C, 5V OUTPUT, 3.5A LOAD CURRENT
RADIATED EMI CURVE
toc46
70
60
50
40
CISPR-22 CLASS B QP LIMIT
30
VERTICAL
20
SCAN
10
0
HORIZONTAL
SCAN
-10
30
100
FREQUENCY (MHz)
CONDITION: MEASURED ON THE MAX17633CEVKIT#
1000
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Pin Configuration
BST
20
NC
16
LX
19
LX
18
LX
17
+
1
PGND
IN
15
PGND
*EP
2
14
13
12
IN
IN
MAX17633A
MAX17633B
MAX17633C
3
4
NC
EXTVCC
EN/UVLO
MODE/SYNC
11
RESET
5
6
10
9
7
8
RT
INTVCC
SGND
SS
FB
20-PIN TQFN (4mm × 4mm)
*EXPOSED PAD
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Pin Description
PIN
NAME
FUNCTION
Power Ground Pin of the Converter. Connect externally to the power ground plane. Refer to the
MAX17633 EV kit datasheet for a layout example
1, 15
PGND
Power-Supply Input Pin. 4.5V to 36V input-supply range. Decouple to PGND with a minimum of 2.2μF
capacitor; place the capacitor close to the IN and PGND pins.
2, 3,14
4
IN
Enable/Undervoltage Lockout Pin. Drive EN/UVLO high to enable the output. Connect to the center of
EN/UVLO the resistor-divider between IN and SGND to set the input voltage at which the part turns on. Connect to
the IN pin for always on operation. Pull low for disabling the device.
Open-Drain RESET Output. The RESET output is driven low if FB drops below 92% of its set value.
RESET goes high 1024 cycles after FB rises above 95% of its set value
5
6
RESET
5V LDO Output of the Part. Bypass INTVCC with a 2.2μF ceramic capacitance to SGND. LDO doesn't
support the external loading on INTVCC.
INTVCC
7
8
SGND
SS
Analog Ground
Soft-Start Input. Connect a capacitor from SS to SGND to set the soft-start time.
Feedback Input. Connect the output-voltage node (V
) to FB for MAX17633A and MAX17633B.
OUT
9
FB
RT
Connect FB to the center node of an external resistor-divider from the output to SGND to set the output
voltage for MAX17633C. See the Adjusting Output Voltage section for more details.
Programmable Switching Frequency Input. Connect a resistor from RT to SGND to set the regulator’s
switching frequency between 400kHz and 2.2MHz. Leave RT open for the default 500kHz frequency.
See the Setting the Switching Frequency (RT) section for more details.
10
MODE/SYNC Pin Configures the Device to Operate in PWM, PFM, or DCM Modes of Operation. Leave
MODE/SYNC OPEN for PFM operation (pulse skipping at light loads). Connect MODE/SYNC to SGND
for constant-frequency PWM operation at all loads. Connect MODE/SYNC to INTVCC for DCM operation
at light loads.The device can be synchronized to an external clock using this pin. See the Mode Selection
and External Clock Synchronization (MODE/SYNC) section for more details.
MODE/
SYNC
11
12
External Power Supply Input Reduces the Internal-LDO Loss. Connect it to buck output when it is pro-
grammed to 5V only. When EXTVCC is not used, connect it to SGND.
EXTVCC
13, 16
17–19
20
NC
LX
Not Connected
Switching Node Pins. Connect LX pins to the switching side of the inductor.
Boost Flying Capacitor. Connect a 0.1μF ceramic capacitor between BST and LX.
BST
Exposed Pad. Always connect EP to the SGND pin of the IC. Also, connect EP to a large SGND plane
with several thermal vias for best thermal performance. Refer to the MAX17633 EV kit data sheet for an
example of the correct method for EP connection and thermal vias.
—
EP
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Functional Diagram
MAX17633A/MAX17633B/MAX17633C
EXTVCC
BST
INTVCC
SGND
LDO
IN
CURRENT-
SENSE
LOGIC
EN/UVLO
ENOK
HICCUP
1.215V
LX
PWM/PFM/HICCUP
LOGIC
RT
OSCILLATOR
PGND
*S1
ERROR AMPLIFIER /
LOOP COMPENSATION
FB
*S3
THERMAL
SHUTDOWN
R1
*S2
R2
SLOPE
COMPENSATION
INTVCC
SWITCH-OVER LOGIC
MODE/SYNC
MODE
SELECTION
LOGIC
SS
HICCUP
ENOK
RESET
FB
RESET
LOGIC
*S1 – CLOSE, *S2,*S3 – OPEN FOR MAX17633C
*S1 – OPEN, *S2,*S3 – CLOSE FOR MAX17633A/MAX17633B
R1 – 132.7kΩ, R2 – 29.1kΩ FOR MAX17633B
R1 – 77.7kΩ, R2 – 29.1kΩ FOR MAX17633A
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
loads. If the state of the MODE/SYNC pin is high (> V
M_
Detailed Description
), the device operates in DCM mode at light loads.
DCM
The MAX17633 is a high-efficiency, high-voltage, syn-
chronous step-down DC-DC converter with integrated
MOSFETs operating over an input voltage range of 4.5V
to 36V. It can deliver up to 3.5A current. The MAX17633
is available in three variants MAX17633A, MAX17633B,
and MAX17633C. The MAX17633A and MAX17633B are
the fixed 3.3V and fixed 5V output voltage parts, respec-
tively. MAX17633C is an adjustable output voltage (from
During external clock synchronization the device oper-
ates in PWM mode, irrespective of whether PWM or DCM
mode is set. When 16 external clock rising edges are
detected on the MODE/SYNC pin, the internal oscillator
frequency set by RT pin (f ) changes to external clock
SW
frequency. The device remains in PWM mode until EN/
UVLO or input power is cycled. The external clock fre-
quency must be between 1.1 x f
and 1.4 x f . The
0.9V up to 90% of V ) part. Built-in compensation across
SW
SW
IN
minimum external clock pulse width should be greater
than 50ns. The off-time duration of the external clock
should be at least 160ns.
the output voltage range eliminates the need for exter-
nal components. The feedback (FB) voltage regulation
accuracy over -40ºC to +125ºC is ±1.3% for MAX17633A,
MAX17633B, and MAX17633C.
If PFM mode of operation is set, the device ignores the
external clock pulses and remains in PFM mode. Thus,
external clock synchronization is not supported in PFM
mode. See the MODE/SYNC section in the Electrical
Characteristics table for details.
The device features a peak-current-mode control archi-
tecture. An internal transconductance error amplifier
produces an integrated error voltage at an internal node,
which sets the duty cycle using a PWM comparator, a
high-side current-sense amplifier, and a slope-compen-
sation generator. At each rising edge of the clock, the
high-side MOSFET turns on and remains on until either
the appropriate or maximum duty cycle is reached, or
the peak current limit is detected. During the high-side
MOSFET’s on-time, the inductor current ramps up. During
the second half of the switching cycle, the high-side
MOSFET turns off and the low-side MOSFET turns on.
The inductor releases the stored energy as its current
ramps down and provides current to the output.
PWM Mode Operation
In PWM mode, the inductor current is allowed to go
negative. PWM operation provides constant frequency
operation irrespective of loading, and is useful in applica-
tions sensitive to switching frequency. However, the PWM
mode of operation gives lower efficiency at light loads
compared to PFM and DCM modes of operation.
PFM Mode Operation
PFM mode of operation disables negative inductor cur-
rent and additionally skips pulses at light loads for high
efficiency. In PFM mode, the inductor current is forced
The device features a MODE/SYNC pin that can be used
to operate the device in PWM, PFM, or DCM control
schemes. The device features adjustable-input undervolt-
age lockout, adjustable soft-start, open drain RESET, and
external clock synchronization features. The MAX17633
offers a low minimum on-time that enables designing the
converter at higher switching frequencies, which helps
reduce the solution size.
to a fixed peak of I
(1.2A typ) every clock cycle until
PFM
the output rises to 102.3% of the set nominal output volt-
age. Once the output reaches 102.3% of the set nominal
output voltage, both the high-side and low-side FETs are
turned off and the device enters hibernate operation until
the load discharges the output to 101.1% of the set nomi-
nal output voltage. Most of the internal blocks are turned
off in hibernate operation to reduce quiescent current.
After the output falls below 101.1% of the set nominal
output voltage, the device comes out of hibernate opera-
tion, turns on all internal blocks, and again commences
the process of delivering pulses of energy to the output
until it reaches 102.3% of the set nominal output voltage.
The advantage of PFM mode is higher efficiency at light
loads because of lower quiescent current drawn from the
supply. The disadvantage is that the output-voltage ripple
is higher compared to PWM or DCM modes of operation
and switching frequency is not constant at light loads.
Mode Selection and External Clock Synchro-
nization (MODE/SYNC)
The MAX17633 supports PWM, PFM, and DCM modes
of operation. The device enters the required mode of
operation based on the setting of the MODE/SYNC pin
as detected within 1.5ms after V
and EN/UVLO volt-
CC
ages exceed their respective UVLO rising thresholds
(V , V ). If the MODE/SYNC pin is open,
INTVCC_UVR ENR
the device operates in PFM mode at light loads. If the
state of the MODE/SYNC pin is low (< V ), the
M_PWM
device operates in constant-frequency PWM mode at all
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
DCM Mode Operation
Table 1. Switching Frequency vs.
DCM mode of operation features constant frequency
operation down to lighter loads than PFM mode, by
disabling negative inductor current at light loads. DCM
operation offers efficiency performance that lies between
PWM and PFM modes. The output-voltage ripple in DCM
mode is comparable to PWM mode and relatively lower
compared to PFM mode.
R
Resistor
RT
SWITCHING FREQUENCY
RRT RESISTOR
(KΩ)
(KHZ)
400
500
50.8
OPEN
40.2
500
2200
8.06
Linear Regulator (INTVCC and EXTVCC)
The MAX17633 has an internal low dropout (LDO) regu-
lator that powers INTVCC from IN. This LDO is enabled
during power-up or when EN/UVLO is above 0.75V (typ).
An internal switch connects the EXTVCC to INTVCC. The
switch is open during power up. If INTVCC is above its
UVLO threshold and EXTVCC is greater than 4.7V (typ),
then the internal LDO is disabled and INTVCC is pow-
ered from EXTVCC. Powering INTVCC (INTVCC output
voltage is 5V typ) from EXTVCC increases efficiency at
higher input voltages. Bypass INTVCC to SGND with a
2.2µF low-ESR ceramic capacitor. INTVCC powers the
internal blocks and the low-side MOSFET driver and
recharges the external bootstrap capacitor
Where R is in kΩ and f
open forces the device to operate at a default switching
frequency of 500kHz. See Table 1 for R resistor values
for a few common switching frequencies.
is in kHz. Leaving the RT pin
RT
SW
RT
Operating Input-Voltage Range
The minimum and maximum operating input voltages for
a given output-voltage setting should be calculated as
follows:
V
+ I
(
× R
(
+ R
DCR(MAX) DS_ONL(MAX)
)
)
OUT
OUT(MAX)
V
=
IN(MIN)
1 - f
× t
(
)
SW(MAX)
OFF_MIN(MAX)
The MAX17633 employs an undervoltage lockout circuit
that forces the converter off when INTVCC falls below
+ I
(
× R
(
− R
)
)
DS_ONH(MAX)
DS_ONL(MAX)
OUT MAX
(
)
V
(3.8V typ). The buck converter can be
INTVCC_UVF
immediately enabled again when INTVCC > V
INTVCC_
V
OUT
(4.2typ). The 400mV UVLO hysteresis prevents chat-
UVR
V
=
f
IN MAX
(
)
× t
tering on power-up and power-down.
SW MAX
ON_MIN MAX
( )
(
)
In applications where the buck converter output is con-
nected to the EXTVCC pin, if the output is shorted to
ground then the transfer from EXTVCC to internal LDO
happens seamlessly without any impact on the normal
functionality. Connect the EXTVCC pin to SGND when
not in use.
where:
V
= Steady-state output voltage,
OUT
I
= Maximum load current,
OUT(MAX)
R
= Worst-case DC resistance of the inductor,
DCR
f
t
= Maximum switching frequency,
SW(MAX)
Setting the Switching Frequency (RT)
= Worst-case minimum switch off-time
OFF_MIN(MAX)
The switching frequency of the device can be pro-
grammed from 400kHz to 2.2MHz by using a resistor con-
nected from the RT pin to SGND. The switching frequency
(160ns),
t
Worst-case minimum switch on-time
ON_MIN(MAX) =
(80ns),
(f ) is related to the resistor(R ) connected at the RT
SW
RT
R
and R
= Worst case
DS_ONH(MAX)
pin by the following equation:
DS_ONL(MAX)
on-state resistance of low-side and high-side internal
MOSFETs respectively.
21000
R
− 1.7
RT
f
SW
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Overcurrent Protection/Hiccup Mode
Thermal-Shutdown Protection
The device is provided with a robust overcurrent protec-
tion (OCP) scheme that protects the device under over-
load and output short-circuit conditions. A cycle-by-cycle
peak current limit turns off the high-side MOSFET when-
ever the high-side switch current exceeds an internal limit
Thermal-shutdown protection limits junction temperature
in the device. When the junction temperature of the device
exceeds +165ºC, an on-chip thermal sensor shuts down
the device, allowing the device to cool. The device turns
on with soft-start after the junction temperature reduces
of I
(5.4A typ). A runaway current limit on the
by 10°C. Carefully evaluate the total power dissipation
(see the Power Dissipation section) to avoid unwanted
triggering of the thermal shutdown in normal operation.
PEAK-LIMIT
high-side switch current at I
(6.4A typ)
RUNAWAY_LIMIT
protects the device under high input voltage, output short-
circuit conditions when there is insufficient output voltage
available to restore the inductor current that has built up
during the on period of the step-down converter. One
occurrence of the runaway current limit triggers hiccup
Applications Information
Input Capacitor Selection
The input filter capacitor reduces peak currents drawn
from the power source and reduces noise and voltage
ripple on the input caused by the circuit’s switching.
mode. In addition, if feedback voltage drops to V
FB_HICF
(0.58V typ) due to a fault condition, hiccup mode is trig-
gered 1024 clock cycles after soft-start is completed. In
hiccup mode, the converter is protected by suspending
switching for a hiccup timeout period of 32,768 clock
cycles of half the switching frequency. Once the hiccup
timeout period expires, soft-start is attempted again. Note
that when soft-start is attempted under overload condi-
The input capacitor RMS current requirement (I
defined by the following equation:
) is
RMS
V
×( V
V
- V
)
OUT
IN
IN
OUT
√
×
OUT(MAX)
I
= I
RMS
tion, if feedback voltage does not exceed V
, the
FB_HICF
where, I
is the maximum load current. I
has
RMS
OUT(MAX)
device continues to switch at half the programmed switch-
ing frequency for the time duration of the programmed
soft-start time and 1024 clock cycles. Hiccup mode of
operation ensures low power dissipation under output
short-circuit conditions.
a maximum value when the input voltage equals twice
the output voltage (V = 2 x V ), so I
=
RMS(MAX)
IN
OUT
I
/2. Choose an input capacitor that exhibits less
OUT(MAX)
than +10°C temperature rise at the RMS input current for
optimal long-term reliability. Use low-ESR ceramic capaci-
tors with high-ripple-current capability at the input. X7R
capacitors are recommended in industrial applications for
their temperature stability. Calculate the input capacitance
using the following equation:
RESET Output
The device includes a RESET comparator to monitor the
status of output voltage. The open-drain RESET output
requires an external pullup resistor. RESET goes high
(high impedance) with a delay of 1024 switching cycles
I
× D × 1 − D
(
× ∆ V
)
OUT MAX
(
)
C
=
after the regulator output increases above V
and
IN
FB_OKR
η × f
SW
IN
95% of V
tor output voltage drops to below V
. RESET goes low when the regula-
FB_REG
and 92% of
where:
D = V
FB_OKF
V
. RESET also goes low during thermal shutdown
FB_REG
/V is the duty ratio of the controller,
OUT IN
or when the EN/UVLO pin goes below V
.
ENF
f
= Switching frequency,
SW
Prebiased Output
ΔV = Allowable input voltage ripple,
IN
When the device starts into a prebiased output, both the
high-side and the low-side switches are turned off so
that the converter does not sink current from the output.
Highside and low-side switches do not start switching until
the PWM comparator commands the first PWM pulse, at
which point switching commences. The output voltage is
then smoothly ramped up to the target value in alignment
with the internal reference.
η = Efficiency.
In applications where the source is located distant from
the device input, an appropriate electrolytic capacitor
should be added in parallel to the ceramic capacitor
to provide necessary damping for potential oscillations
caused by the inductance of the longer input power path
and input ceramic capacitor.
Maxim Integrated
│ 17
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
ered while selecting the output capacitor. Derating curves
are available from all major ceramic capacitor vendors
Inductor Selection
Three key inductor parameters must be specified for
operation with the device: inductance value (L), inductor
Soft-Start Capacitor Selection
saturation current (I
), and DC resistance (R
). The
SAT
DCR
The device implements adjustable soft-start operation to
reduce inrush current. A capacitor connected from the SS
pin to SGND programs the soft-start time. The selected
switching frequency and output voltage determine the
inductor value as follows:
output capacitance (C
determine the minimum required soft-start capacitor as
follows:
) and the output voltage (V
)
SEL
OUT
1.5
Where V
and f
are nominal values and f
is in
OUT
SW
SW
−6
Hz. Select an inductor whose value is nearest to the value
calculated by the previous formula. Select a low-loss
inductor closest to the calculated value with acceptable
dimensions and having the lowest possible DC resis-
tance. The saturation current rating (I
must be high enough to ensure that saturation can occur
C
≥ 28 × 10 × C
× V
SS
SEL OUT
The soft-start time (t ) is related to the capacitor con-
SS
nected at SS (C ) by the following equation:
SS
) of the inductor
SAT
C
SS
t
=
SS
−6
5.55 × 10
only above the peak current-limit value of I
(5.4A typ).
PEAK_LIMIT
For example, to program a 1ms soft-start time, a 5.6nF
capacitor should be connected from the SS pin to SGND.
Note that, during start-up, device operates at half the
programmed switching frequency until the output voltage
reaches 66.7% of set output nominal voltage.
Output Capacitor Selection
X7R ceramic output capacitors are preferred due to
their stability over temperature in industrial applications.
Output capacitor is calculated and sized to support a 50%
of maximum output current as the dynamic step load, and
to contain the output-voltage deviation to within ±3% of
the output voltage. The minimum required output capaci-
tance can be calculated as follows:
Setting the Input Undervoltage-Lockout Level
The device offers an adjustable input undervoltage-lockout
level. Set the voltage at which the device turns on with
a resistive voltage-divider connected from INto SGND.
Connect the center node of the divider to the EN/UVLO pin.
I
× t
1
2
STEP RESPONSE
C
=
×
OUT
∆ V
Choose R
to be 3.3MΩ and then calculate R
TOP
BOTTOM
OUT
as follows:
0.35
t
≅
R
× 1.215
− 1.215
RESPONSE
TOP
f
C
R
=
BOTTOM
V
(
)
INU
where:
I
t
= Load current step,
STEP
where V
to turn on. Ensure that V
is the voltage at which the device is required
INU
= Response time of the controller,
= Allowable output-voltage deviation,
is higher than 0.8 x V
INU OUT
RESPONSE
to avoid hiccup during slow power-up (slower than soft-
start) or power-down. If the EN/UVLO pin is driven from
an external signal source, a series resistance of minimum
1kΩ is recommended to be placed between the output
pin of the signal source and the EN/UVLO pin to reduce
voltage ringing on the line.
ΔV
OUT
f
= Target closed-loop crossover frequency.
C
Select f to be 1/10th of f
less than or equal to 800kHz. If the switching frequency is
more than 800kHz, select f to be 80kHz. Actual derating
for the switching frequencies
C
SW
C
of ceramic capacitors with DC-voltage must be consid-
Maxim Integrated
│ 18
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
V
V
OUT
IN
MAX17633A
MAX17633B
MAX17633C
MAX17633C
R
U
R
TOP
EN/UVLO
FB
R
B
R
BOTTOM
Figure 1. Setting the Input Undervoltage Lockout
Figure 2. Setting the Output Voltage
where:
Adjusting Output Voltage
Set the output voltage with a resistive voltage-divider
P
= Output power
OUT
connected from the output-voltage node (V
(see Figure 2). Connect the center node of the divider
to the FB pin for MAX17633C. Connect the output-
) to SGND
OUT
η = Efficiency of the converter
= DC resistance of the inductor.
R
DCR
See Typical Operating Characteristics for more informa-
voltage node (V
) to the FB pin for MAX17633A and
OUT
tion on efficiency at typical operating conditions.
MAX17633B. Use the following procedure to choose the
resistive voltage-divider values:
For a typical multilayer board, the thermal performance
metrics for the package are given below:
Calculate resistor R from the output to the FB pin as
U
follows:
θ
= 26ºC/W
= 2ºC/W
JC
JA
270
R
=
f
θ
U
× C
C
OUT
The junction temperature of the device can be estimated
where R is in kΩ, crossover frequency f is in Hz, and
at any given maximum ambient temperature (T
from the following equation:
)
U
C
A(MAX)
the output capacitor C
is in F. Calculate resistor R
OUT
B
connected from the FB pin to SGND as follows:
T
= T
+ θ × P
(
)
J(MAX)
A(MAX) JA LOSS
R
× 0.9
U
R
=
B
V
− 0.9
If the application has a thermal-management system that
ensures that the exposed pad of the device is maintained
(
)
OUT
at a given temperature (T
sinks, then the junction temperature of the device can be
estimated at any given maximum ambient temperature as:
) by using proper heat
R is in kΩ.
EP(MAX)
B
Select an appropriate f and C
combination of R and R is less than 50kΩ.
so that the parallel
C
U
OUT
B
T
= T
+
θ
(
× P
JC LOSS
)
J(MAX)
EP(MAX)
Power Dissipation
At a particular operating condition, the power losses that
lead to a temperature rise of the part are estimated as fol-
lows:
Note: Junction temperatures greater than +125°C
degrade operating lifetimes.
1
η
2
P
= P
(
×
− 1 − I
× R
OUT DCR
LOSS
OUT
(
))
(
)
P
= V
× I
OUT
OUT OUT
Maxim Integrated
│ 19
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
When routing the circuitry around the IC, the analog
small-signal ground and the power ground for switching
currents must be kept separate. They should be con-
nected together at a point where switching activity is at a
minimum. This helps keep the analog ground quiet. The
ground plane should be kept continuous/unbroken as
far as possible. No trace carrying high switching current
should be placed directly over any ground plane discon-
tinuity
PCB Layout Guidelines
All connections carrying pulsed currents must be very
short and as wide as possible. The inductance of these
connections must be kept to an absolute minimum due to
the high di/dt of the currents. Since inductance of a cur-
rent-carrying loop is proportional to the area enclosed by
the loop, if the loop area is made very small, inductance
is reduced. Additionally, small-current loop areas reduce
radiated EMI.
PCB layout also affects the thermal performance of the
design. A number of thermal throughputs that connect to a
large ground plane should be provided under the exposed
pad of the part for efficient heat dissipation.
A ceramic input filter capacitor should be placed close
to the IN pins of the IC. This eliminates as much trace
inductance effects as possible and gives the IC a cleaner
voltage supply. A bypass capacitor for the INTVCCpin
also should be placed close to the pin to reduce effects of
trace impedance.
For a sample layout that ensures first pass success, refer
to the MAX17633 evaluation kit layout available at www.
maximintegrated.com.
Typical Application Circuits
Typical Application Circuit —Adjustable 3.3V Output
V
IN
4.5V TO 36V
C1
2.2μF
2x
EN/UVLO
IN
IN
BST
IN
RT
C5
0.1μF
MODE/SYNC
INTVCC
L1
LX
LX
5.6μH
3.3V, 3.5A
V
OUT
MAX17633C
C3
2.2μF
C4
47μF
2x
R1
76.8kΩ
LX
SGND
RESET
FB
PGND
SS
PGND
EXTVCC
f
= 500kHz
SW
R2
L1: XAL5050-562ME
C1: GRM32ER72A225KA35
C4: GRM32ER70J476KE20
28.7kΩ
C2
5600pF
MODE/SYNC:
1. CONNECT TO SGND FOR PWM MODE
2. CONNECT TO INTVCC FOR DCM MODE
3. LEAVE OPEN FOR PFM MODE
Figure 3. Adjustable 3.3V Output with 500kHz Switching Frequency
Maxim Integrated
│ 20
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Typical Application Circuits (continued)
Typical Application Circuit—Adjustable 5V Output
V
IN
6.5V TO 36V
C1
2.2μF
2x
EN/UVLO
IN
IN
BST
IN
RT
C5
0.1μF
MODE/SYNC
INTVCC
L1
LX
LX
6.8μH
5V, 3.5A
V
OUT
MAX17633C
C3
2.2μF
C4
22μF
2x
R1
133kΩ
LX
SGND
RESET
FB
PGND
SS
PGND
EXTVCC
f
= 500kHz
SW
R2
L1: XAL5050-682ME
C1: GRM32ER72A225KA35
C4: GRM32ER71A226K
28.7kΩ
C2
5600pF
V
OUT
MODE/SYNC:
1. CONNECT TO SGND FOR PWM MODE
2. CONNECT TO INTVCC FOR DCM MODE
3. LEAVE OPEN FOR PFM MODE
Figure 4. Adjustable 5V Output with 500kHz Switching Frequency
Typical Application Circuit —Fixed 3.3V Output
V
IN
4.5V TO 36V
C1
2.2μF
2x
EN/UVLO
IN
IN
BST
IN
RT
C5
0.1μF
MODE/SYNC
INTVCC
L1
LX
LX
5.6μH
3.3V, 3.5A
V
OUT
MAX17633A
C3
2.2μF
C4
47μF
2x
LX
SGND
RESET
FB
PGND
SS
PGND
EXTVCC
f
= 500kHz
SW
L1: XAL5050-562ME
C2
5600pF
C1: GRM32ER72A225KA35
C4: GRM32ER70J476KE20
MODE/SYNC:
1. CONNECT TO SGND FOR PWM MODE
2. CONNECT TO INTVCC FOR DCM MODE
3. LEAVE OPEN FOR PFM MODE
Figure 5. Fixed 3.3V Output with 500kHz Switching Frequency
Maxim Integrated
│ 21
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Typical Application Circuits (continued)
Typical Application Circuit —Fixed 5V Output
V
IN
6.5V TO 36V
C1
2.2μF
2x
EN/UVLO
IN
IN
BST
IN
RT
C5
0.1μF
MODE/SYNC
INTVCC
L1
LX
LX
6.8μH
5V, 3.5A
V
OUT
MAX17633B
C3
2.2μF
C4
22μF
LX
SGND
2x
RESET
FB
PGND
SS
PGND
EXTVCC
f
= 500kHz
SW
C2
5600pF
L1: XAL5050-682ME
C1: GRM32ER72A225KA35
C4: GRM32ER71A226K
MODE/SYNC:
1. CONNECT TO SGND FOR PWM MODE
2. CONNECT TO INTVCC FOR DCM MODE
3. LEAVE OPEN FOR PFM MODE
Figure 6. Fixed 5V Output with 500kHz Switching Frequency
Ordering Information
OUTPUT
PART NUMBER
VOLTAGE
PIN-PACKAGE
(V)
20 TQFN-EP*
(4mm x 4mm)
MAX17633AATP+
MAX17633AATP+T
MAX17633BATP+
MAX17633BATP+T
MAX17633CATP+
MAX17633CATP+T
3.3
20 TQFN-EP*
(4mm x 4mm)
3.3
20 TQFN-EP*
(4mm x 4mm)
5
20 TQFN-EP*
(4mm x 4mm)
5
20 TQFN-EP*
(4mm x 4mm)
Adjustable
Adjustable
20 TQFN-EP*
(4mm x 4mm)
+Denotes a lead(Pb)-free/RoHS compliant package
*EP = Exposed pad.
T = Tape and reel.
Maxim Integrated
│ 22
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MAX17633
4.5V to 36V, 3.5A, High Efficiency,
Synchronous Step-Down, DC-DC Converter
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
4/18
Initial release
—
Updated the General Description, Benefits and Features, Electrical Characteristics,
Pin Description, Detailed Description, and Operating Input-Voltage Range sections,
and TOC01–TOC12; replaced the Typical Application Circuit and Mode Selection and
External Clock Synchronization (MODE/SYNC); added TOC45–TOC46
4–5, 7–11,
14, 16, 18, 19
1
2
2/19
7/20
Updated the General Description, Benefits and Features, Electrical Characteristics,
Pin Configuration, Pin Description, Detailed Description, PFM Mode Operation,
Overcurrent Protection/Hiccup Mode, Output Capacitor Selection, Thermal-Shutdown
Protection, Power Dissipation, and added the MAX17633AATP+T, MAX17633BATP+T
and MAX17633CATP+T to the Ordering Information section; updated TOC34,
TOC36–TOC39, TOC45, TOC46 and replaced the Typical Application Circuit
1–3, 5, 9–13,
15–19, 22
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
©
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
2020 Maxim Integrated Products, Inc.
│ 23
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