MAX17501FATB+ [MAXIM]
60V, 500mA, Ultra-Small, High-Efficiency,Synchronous Step-Down DC-DC Converter; 60V ， 500毫安，超小尺寸，高效率，同步降压型DC -DC转换器
| 型号： | MAX17501FATB+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 60V, 500mA, Ultra-Small, High-Efficiency,Synchronous Step-Down DC-DC Converter |
| 文件： | 总16页 (文件大小：2992K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-6244; Rev 0; 5/12
E V A L U A T I O N K I T A V A I L A B L E
General Description
Benefits and Features
The MAX17501 high-efficiency, high-voltage, synchro-
nous step-down DC-DC converter operates over a 4.5V to
60V input voltage range and is designed for a wide range
of applications. The ultra-wide-input operation makes it
ideal for not only industrial control and building automa-
tion, but also base stations, telecom, home entertainment
and automotive applications. It delivers output currents
up to 500mA, at output voltages of 3.3V and 5V. The out-
put voltage is accurate within Q1.6% over temperature.
The device operates over the -40NC to +125NC industrial
temperature range and is available in a tiny, 10-pin (3mm
x 2mm) TDFN with an exposed pad.
S Eliminate External Components and Reduce Total
Cost
No Schottky-Synchronous Operation for High
Efficiency and Reduced Cost
Internal Compensation for Ultra-Compact
Layout
All-Ceramic Capacitors
S Reduce Number of DC-DC Regulators to Stock
Wide 4.5V to 60V Operating-Voltage Range
Fixed 3.3V and 5V Output
Delivers Up to 500mA Over Temperature
600kHz Switching Frequency
The device features peak-current-mode control with
pulse-width modulation (PWM). The PWM operation
ensures constant switching frequency at all operating
conditions. The low-resistance, on-chip, pMOS/nMOS
switches ensure high efficiency at full load while minimiz-
ing the critical inductances, making the layout a much
simpler task compared to discrete solutions.
S Reduce Power Dissipation
Peak Efficiency > 90%
Shutdown Current = 1µA (typ)
S Operate Reliably in Adverse Industrial Environments
Hiccup-Mode Current Limit and Autoretry Startup
Built-In Output-Voltage Monitoring (Open-Drain
RESET Pin)
The device offers fixed switching frequency of 600kHz. To
reduce input inrush current, the device offers an adjust-
able voltage soft-start feature with an external capacitor
from the SS pin to ground. 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 RESET pin provides a
delayed power-good signal to the system upon achieving
successful regulation of the output voltage. The device
supports hiccup-mode current-limit protection for low
power dissipation under overload and output short-circuit
conditions.
Resistor-Programmable UVLO Threshold
Increased Safety with Adjustable Soft-Start and
Prebiased Power-Up
Optional Adjustable Output and PFM (Available
Upon Factory Request)
-40NC to +125NC Industrial Temperature Range
Typical Operating Circuit
L1
47µH
V
V
OUT
5V, 500mA
IN
24V 20%
V
LX
IN
Applications
C1
1µF
1206
C4
10µF, 6.3V
1206
R1
3.32MI
1
2
3
Industrial Process Control
HVAC and Building Control
General-Purpose Point-of-Load
Base Station, VOIP, Telecom
Home Theater
PGND
EN/UVLO
JU1
R2
866kI
MAX17501F
GND
V
CC
C2
1µF
FB/VO
RESET
SS
C3
3300pF
Automotive
N.C.
RESET
Battery-Powered Equipment
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part, refer to www.maxim-ic.com/MAX17501.related.
����������������������������������������������������������������� Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
ABSOLUTE MAXIMUM RATINGS
IN
V
to GND............................................................-0.3V to +70V
Continuous Power Dissipation (T = +70NC)
A
EN/UVLO to GND......................................... -0.3V to V + 0.3V
10-Pin TDFN (derate 14.9mW/NC above +70NC)
IN
LX to PGND...........................................................-0.3V to +70V
FB, RESET, COMP, SS to GND................................. -0.3V to 6V
(multilayer board) ...................................................1188.7mW
Operating Temperature Range........................ -40NC to +125NC
Junction Temperature .....................................................+150NC
Storage Temperature Range............................ -65NC to +160NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
V
to GND.............................................................-0.3V to +6V
CC
GND to PGND ......................................................-0.3V to +0.3V
LX Total RMS Current........................................................ Q1.6A
Output Short-Circuit Duration....................................Continuous
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-
tion 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 THERMAL CHARACTERISTICS (Note 1)
Thermal Resistance
TDFN
Junction-to-Ambient Thermal Resistance (B ) .......67.3NC/W
Junction-to-Case Thermal Resistance (B )............18.2NC/W
JC
JA
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.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(V = 24V, V
= V
= 0V, C
= C
= 1FF, V
= 1.5V, C = 3300pF, V = 0.98 x V , LX = unconnected, RESET =
SS FB OUT
IN
GND
PGND
VIN
VCC
EN
unconnected. T = T = -40NC to +125NC, unless otherwise noted. Typical values are at T = +25NC. All voltages are referenced to GND,
A
J
A
unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INPUT SUPPLY (V
)
IN
Input Voltage Range
V
4.5
60
3.5
V
IN
I
V
= 0V, shutdown mode
0.9
3.7
5
FA
IN-SH
EN
Input Supply Current
V
V
= 12V
= 24V
5.2
Normal switching
mode, V = 0.8V
IN
I
mA
IN-SW
COMP
6.75
IN
ENABLE/UVLO (EN/UVLO)
V
V
V
V
rising
1.194 1.218 1.236
1.114 1.135 1.156
0.75
ENR
EN
EN
EN
EN Threshold
V
falling
falling, true shutdown
V
ENF
V
EN-TRUESD
EN Input Leakage Current
I
7
200
nA
EN
LDO
6V < V < 12V, 0mA < I
< 10mA,
IN
VCC
V
Output Voltage Range
V
4.65
5
5.35
80
V
CC
CC
12V < V < 60V, 0mA < I
< 2mA
IN
VCC
V
V
Current Limit
Dropout
I
V
V
V
V
= 4.3V, V = 12V
17
40
mA
V
CC
VCC-MAX
CC
IN
V
= 4.5V, I = 5mA
VCC
4.1
CC
CC-DO
IN
V
rising
falling
3.85
3.55
4
4.15
3.85
CC-UVR
CC
CC
V
UVLO
V
CC
V
3.7
CC-UVF
����������������������������������������������������������������� Maxim Integrated Products
2
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(V = 24V, V
= V
= 0V, C
= C
= 1FF, V
= 1.5V, C = 3300pF, V = 0.98 x V
, LX = unconnected, RESET =
unconnected. T = T = -40NC to +125NC, unless otherwise noted. Typical values are at T = +25NC. All voltages are referenced to GND,
IN GND
PGND
VIN
VCC
EN
SS FB OUT
A
J
A
unless otherwise noted.) (Note 2)
PARAMETER
LX
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
= 0V, T = +25NC,
A
EN
LX
LX Leakage Current
I
1
FA
LX_LKG
= (V
+ 1V) to (V - 1V)
PGND
IN
SOFT-START (SS)
Switchover to Internal Reference-
Voltage Threshold
V
863
4.7
880
5
898
5.3
mV
SS-TH
Charging Current
I
V
= 0.5V
FA
SS
SS
FEEDBACK (FB)
MAX17501E,
6.8
6.8
12
12
17
17
FA
FA
V
= 3.3V
FB
FB Input Bias Current
I
T = +25NC
A
FB
MAX17501F,
= 5V
V
FB
OUTPUT VOLTAGE (V
Output Voltage Range
CURRENT LIMIT
)
OUT
MAX17501E only
MAX17501F only
3.248
4.922
3.3
5
3.352
5.08
Peak-Current-Limit Threshold
I
0.585 0.685 0.795
A
A
A
PEAK-LIMIT
I
RUNAWAY-
LIMIT
Runaway-Current-Limit Threshold
0.73
0.3
0.865
0.35
1
Valley Current-Limit Threshold
I
0.4
SINK-LIMIT
TIMING
V
V
>
FB
OUT-HICF
560
280
600
300
1
640
320
Switching Frequency
f
MAX17501E/F
kHz
%
SW
V
V
<
FB
OUT-HICF
Events to Hiccup After Crossing
Runaway-Current Limit
V
Undervoltage Trip Level to
OUT
V
V
> 0.95V (soft-start is done)
69.14 71.14 73.14
32,768
OUT-HICF
SS
Cause Hiccup
HICCUP Timeout
Minimum On-Time
Cycles
ns
t
85
94
5
120
ON_MIN
V
= 0.98 x V
FB
FB-
Maximum Duty Cycle
LX Dead Time
D
MAX17501E/F
92
96
%
MAX
REG
ns
����������������������������������������������������������������� Maxim Integrated Products
3
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(V = 24V, V
= V
= 0V, C
= C
= 1FF, V
= 1.5V, C = 3300pF, V = 0.98 x V
, LX = unconnected, RESET =
unconnected. T = T = -40NC to +125NC, unless otherwise noted. Typical values are at T = +25NC. All voltages are referenced to GND,
IN GND
PGND
VIN
VCC
EN
SS FB OUT
A
J
A
unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RESET
0.02
0.45
V
I
= 1mA
RESET Output Level Low
RESET
RESET Output Leakage Current
High
V
V
V
= 1.01 x V
, T = +25NC
FA
FB
FB
FB
OUT
A
V
Threshold for RESET
OUT
V
falling
rising
90.5
93.5
92.5
95.5
1024
94.5
97.5
%
%
OUT-OKF
Assertion
V
Threshold for RESET
OUT
V
OUT-OKR
Deassertion
RESET Deassertion Delay After
FB Reaches 95% Regulation
Cycles
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
Temperature rising
165
10
NC
NC
Note 2: All limits are 100% tested at +25NC. Limits over temperature are guaranteed by design.
Note 3: Guaranteed by design, not production tested.
����������������������������������������������������������������� Maxim Integrated Products
4
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics
(V = 24V, V
= V
= 0V, C
= C
= 1FF, V = 1.5V, C = 3300pF,
V
= 0.98 x V
, unless otherwise noted.)
IN
GND
PGND
VIN
VCC
EN
SS
FB
OUT
EFFICIENCY vs. LOAD CURRENT
(MAX17501E)
EFFICIENCY vs. LOAD CURRENT
(MAX17501F)
OUTPUT VOLTAGE vs. LOAD CURRENT
(MAX17501E)
95
90
85
80
75
70
65
60
55
95
90
85
80
75
70
65
3.310
3.308
3.306
3.304
3.302
3.300
3.298
3.296
3.294
3.292
3.290
V
= 48V
IN
V
= 36V
IN
V
= 48V
V
= 48V
IN
IN
V
= 24V
IN
V
= 24V
V
= 36V
IN
IN
V
= 24V
V
= 36V
IN
IN
V
= 12V
IN
V
= 12V
V = 12V
IN
IN
100 150 200 250 300 350 400 450 500
LOAD CURRENT (mA)
100 150 200 250 300 350 400 450 500
LOAD CURRENT (mA)
0
50 100 150 200 250 300 350 400 450 500
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
(MAX17501F)
SHUTDOWN CURRENT
vs. TEMPERATURE
NO-LOAD SWITCHING CURRENT
vs. TEMPERATURE
1.10
1.05
1.00
0.95
0.90
0.85
0.80
0.75
0.70
5.00
4.95
4.90
4.85
4.80
5.015
5.010
5.005
5.000
4.995
4.990
4.985
V
= 48V
IN
V
= 24V
IN
V
= 36V
IN
V
= 12V
IN
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
0
50 100 150 200 250 300 350 400 450 500
LOAD CURRENT (mA)
EN/UVLO THRESHOLD VOLTAGE
vs. TEMPERATURE
OUTPUT VOLTAGE vs. TEMPERATURE
(MAX17501E)
OUTPUT VOLTAGE vs. TEMPERATURE
(MAX17501F)
1.23
1.22
1.21
1.20
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
3.320
3.315
3.310
3.305
3.300
3.295
3.290
3.285
3.280
5.05
5.04
5.03
5.02
5.01
5.00
4.99
4.98
4.97
4.96
4.95
RISING THRESHOLD
NO LOAD
NO LOAD
FULL LOAD
FULL LOAD
FALLING THRESHOLD
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
����������������������������������������������������������������� Maxim Integrated Products
5
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(V = 24V, V
IN
= V
= 0V, C
= C
= 1FF, V = 1.5V, C = 3300pF,
V
= 0.98 x V , unless otherwise noted.)
OUT
GND
PGND
VIN
VCC
EN
SS
FB
PEAK CURRENT LIMIT
vs. TEMPERATURE
RUNAWAY CURRENT LIMIT
vs. TEMPERATURE
SWITCHING FREQUENCY
vs. TEMPERATURE
1.0
0.9
0.8
0.7
0.6
1.0
0.9
0.8
0.7
0.6
0.5
700
680
660
640
620
600
580
560
540
520
500
0.5
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
SOFT-START FROM V
(MAX17501E)
SOFT-START/SHUTDOWN FROM EN/EVLO
SOFT-START/SHUTDOWN FROM EN/EVLO
IN
(MAX17501E)
(MAX17501F)
MAX17501 toc15
MAX17501 toc13
MAX17501 toc14
EN/UVLO
2V/div
V
EN/UVLO
2V/div
IN
20V/div
V
OUT
I
OUT
200mA/div
2V/div
I
V
OUT
OUT
1V/div
200mA/div
V
OUT
I
OUT
1V/div
200mA/div
RESET
5V/div
RESET
2V/div
RESET
2V/div
400µs/div
1ms/div
1ms/div
SOFT-START WITH 2.5V PREBIAS
(MAX17501F)
SOFT-START FROM V
(MAX17501F)
SOFT-START WITH 2V PREBIAS
IN
(MAX17501E)
MAX17501 toc18
MAX17501 toc16
MAX17501 toc17
V
IN
EN/UVLO
2V/div
EN/UVLO
2V/div
20V/div
V
OUT
V
OUT
1V/div
1V/div
I
OUT
200mA/div
V
OUT
2V/div
RESET
5V/div
RESET
2V/div
RESET
5V/div
400µs/div
400µs/div
400µs/div
����������������������������������������������������������������� Maxim Integrated Products
6
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(V = 24V, V
= V
= 0V, C
= C
= 1FF, V = 1.5V, C = 3300pF, V = 0.98 x V
, unless otherwise noted.)
IN
GND
PGND
VIN
VCC
EN
SS
FB OUT
LOAD TRANSIENT RESPONSE OF
MAX17501F (LOAD CURRENT STEPPED
LOAD TRANSIENT RESPONSE OF
MAX17501E (LOAD CURRENT STEPPED
LOAD TRANSIENT RESPONSE OF
MAX17501E (LOAD CURRENT STEPPED
FROM NO LOAD TO 250mA)
FROM 250mA TO 500mA)
FROM NO LOAD TO 250mA)
MAX17501 toc20
MAX17501 toc21
MAX17501 toc19
V
OUT
(AC)
V
OUT
(AC)
V
OUT
(AC)
100mV/div
50mV/div
50mV/div
I
OUT
I
OUT
200mA/div
200mA/div
I
OUT
100mA/div
20µs/div
20µs/div
20µs/div
LOAD TRANSIENT RESPONSE OF
MAX17501F (LOAD CURRENT STEPPED
SWITCHING WAVEFORMS OF
OUTPUT OVERLOAD PROTECTION OF
MAX17501F AT 500mA LOAD
MAX17501F
FROM 250mA TO 500mA)
MAX17501 toc23
MAX17501 toc24
MAX17501 toc22
V
OUT
(AC)
50mV/div
V
OUT
(AC)
100mV/div
V
OUT
I
LX
2V/div
500mA/div
I
OUT
200mA/div
LX
I
OUT
10V/div
200mA/div
2µs/div
20ms/div
20µs/div
BODEPLOT OF MAX17501E
AT 500mA LOAD
BODEPLOT OF MAX17501F
AT 500mA LOAD
MAX17501 toc25
MAX17501 toc26
BW = 62kHz
PM = 59°
BW = 35kHz
PM = 73°
4 5 6 7891
2
3 4 5 67891
2
4 5 6 7891
2
3 4 5 67891
2
����������������������������������������������������������������� Maxim Integrated Products
7
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Pin Configuration
TOP VIEW
MAX17501
+
PGND
1
2
10 LX
V
9
GND
IN
EN/UVLO
3
4
5
8
7
6
RESET
N.C.
SS
V
CC
EP*
FB
TDFN
(3mm x 2mm)
*EP = EXPOSED PAD, CONNECTED TO GND
Pin Description
PIN
1
NAME
FUNCTION
Power Ground. Connect PGND externally to the power ground plane. Connect GND and PGND
pins together at the ground return path of the V bypass capacitor.
PGND
CC
2
V
Power-Supply Input. The input supply range is from 4.5V to 60V.
IN
Enable/Undervoltage Lockout Input. Drive EN/UVLO high to enable the output voltage. Connect
3
EN/UVLO
to the center of resistive divider between V and GND to set the input voltage (undervoltage
IN
threshold) at which the device turns on. Pull up to V for always on.
IN
4
5
6
V
5V LDO Output. Bypass V
with 1FF ceramic capacitance to GND.
CC
CC
FB
SS
Feedback Input. Directly connect FB to the output.
Soft-Start Input. Connect a capacitor from SS to GND to set the soft-start time.
No Connection. Leave unconnected.
7
N.C.
Open-Drain RESET Output. The RESET output is driven low if FB drops below 92.5% of its set
value. RESET goes high 1024 clock cycles after FB rises above 95.5% of its set value.
8
RESET
GND
LX
9
Analog Ground
Switching Node. Connect LX to the switching side of the inductor. LX is high impedance when the
device is in shutdown mode.
10
Exposed Pad. Connect to the GND pin of the IC. Connect to a large copper plane below the IC to
improve heat dissipation capability.
—
EP
����������������������������������������������������������������� Maxim Integrated Products
8
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Block Diagram
V
CC
PGND
LX
N DRIVER
5µA
SS
SS
MAX17501
HICCUP
P DRIVER
V
IN
CURRENT
SENSE
V
CC
PWM
COMPARATOR
CLK
PWM
LOGIC
LDO
OSC
COMP
HICCUP
SLOPE COMPENSATION
START
EN/UVLO
RESET
RESET
LOGIC
SS
COMP
REFERENCE
SWITCHOVER
LOGIC
900mV
G
M
FB
INTERNAL COMPENSATION
GND
����������������������������������������������������������������� Maxim Integrated Products
9
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
cycle peak-current limit turns off the high-side MOSFET
whenever the high-side switch current exceeds an internal
Detailed Description
limit of 800mA (typ). A runaway-current limit on the high-
side switch current at 900mA (typ) protects the device
under high input voltage, short-circuit conditions when
there is insufficient output voltage available to restore the
inductor current that built up during the on period of the
step-down converter. One occurrence of the runaway-
current limit triggers a hiccup mode. In addition, if due to
a fault condition, output voltage drops to 71.1% (typ) of
its nominal value any time after soft-start is complete, and
hiccup mode is triggered. In hiccup mode, the converter
is protected by suspending switching for a hiccup timeout
period of 32,768 clock cycles. Once the hiccup timeout
period expires, soft-start is attempted again.
The MAX17501 step-down regulator operates from 4.5V
to 60V and delivers up to 500mA load current. Output
voltage regulation accuracy meets Q1.6% over load, line,
and temperature.
Thedeviceusesapeak-current-mode-controlscheme. It
employs synchronous rectification. An internal transcon-
ductance error amplifier produces an integrated error
voltage. The error voltage sets the duty cycle using a
PWM comparator, a high-side current-sense amplifier,
and a slope-compensation generator. At each rising
edge of the clock, the high-side p-channel MOSFET
turns on and remains on until either the appropriate or
maximum duty cycle is reached, or the peak-current
limit is detected.
RESET Output
The device includes a RESET comparator to monitor the
output voltage. The open-drain RESET output requires
an external pullup resistor. RESET can sink 2mA of
current while low. RESET goes high (high impedance)
1024 switching cycles after the regulator output increases
above 95.5% of the designed nominal regulated voltage.
RESET goes low when the regulator output voltage drops
to below 92.5% of the nominal regulated voltage. RESET
goes low during thermal shutdown.
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
n-channel MOSFET turns on. The inductor releases the
stored energy as its current ramps down, and provides
current to the output (the internal low RD
nMOS switches ensure high efficiency at full load).
pMOS/
SON
This device also integrates enable/undervoltage lockout
(EN/UVLO), adjustable soft-start time (SS), and open-
drain reset output (RESET) functionality.
Prebiased Output
When the device starts into a prebiased output, both the
high-side and low-side switches are turned off so that the
converter does not sink current from the output. High-
side and low-side switches do not start switching until
the PWM comparator commands the first PWM pulse, at
which point switching commences first with the high-side
switch. The output voltage is then smoothly ramped up to
the target value in alignment with the internal reference.
Linear Regulator (V
)
CC
An internal linear regulator (V ) provides a 5V nominal
CC
supply to power the internal blocks and the low-side
MOSFET driver. The output of the V
should be bypassed with a 1FF ceramic capacitor to
linear regulator
CC
GND. The device employs an undervoltage-lockout circuit
that disables the internal linear regulator when V
below 3.7V (typ). The 300mV UVLO hysteresis prevents
chattering on power-up/power-down. The internal V
linear regulator can source up to 40mA (typ) to supply
the device and to power the low-side gate driver.
falls
CC
CC
Thermal-Overload Protection
Thermal-overload protection limits total power dissipa-
tion in the device. When the junction temperature of
the device exceeds +165NC, an on-chip thermal sensor
shuts down the device, allowing the device to cool. The
thermal sensor turns the device on again after the junc-
tion temperature cools by 10NC. Soft-start resets during
thermal shutdown. Carefully evaluate the total power
dissipation (see the Power Dissipation section) to avoid
unwanted triggering of the thermal-overload protection in
normal operation.
Switching Frequency
The devices have a fixed 600kHz switching frequency.
The minimum duty ratio at which the devices can oper-
ate is 7.7%.
Overcurrent Protection/Hiccup Mode
The device is provided with a robust overcurrent-
protection scheme that protects the device under
overload and output short-circuit conditions. A cycle-by-
���������������������������������������������������������������� Maxim Integrated Products 10
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
where V , V
, and I
are nominal values. The
IN
OUT
OUT
Applications Information
switching frequency is 600kHz for the MAX17501E/
MAX17501F. Select a low-loss inductor closest to the
calculated value with acceptable dimensions and having
the lowest possible DC resistance.
Input Capacitor Selection
The discontinuous input-current waveform of the buck
converter causes large ripple currents in the input
capacitor. The switching frequency, peak inductor cur-
rent, and the allowable peak-to-peak voltage ripple
that reflects back to the source dictate the capacitance
requirement. The device’s high switching frequency
allows the use of smaller value input capacitors. X7R
capacitors are recommended in industrial applications
for their temperature stability. A minimum value of 1FF
should be used for the input capacitor. Higher values
help reduce the ripple on the input DC bus further. In
applications where the source is located distant from
the device input, an electrolytic capacitor should be
added in parallel to the 1FF ceramic capacitor to provide
necessary damping for potential oscillations caused by
the longer input power path and input ceramic capacitor.
The saturation current rating (I
be high enough to ensure that saturation can occur
only above the peak current-limit value (I
(typ) = 0.8A for the device). A variety of inductors from
different suppliers are available to meet this requirement
(e.g., inductors from the Coilcraft LPS6235 series).
) of the inductor must
SAT
PEAK-LIMIT
See Table 1 to select inductors for 5V and 3.3V fixed
output-voltage applications based on the MAX17501E/
MAX17501F.
Output Capacitor Selection
X7R ceramic output capacitors are preferred due to their
stability over temperature in industrial applications. The
output capacitor is usually sized to support a step load
of 50% of the maximum output current in the application,
such that the output-voltage deviation is contained to 3%
of the output-voltage change. The output capacitance
can be calculated as follows:
Inductor Selection
Three key inductor parameters must be specified
for operation with the device: inductance value (L),
inductor saturation current (I
), and DC resistance
SAT
1 I
×
× t
RESPONSE
∆V
OUT
(R
DCR
). To determine the inductance value, select the
STEP
C
=
OUT
ratio of inductor peak-to-peak ripple current to the DC
average current (LIR). For LIR values that are too high,
the RMS currents are high, and therefore the inductor
I2R losses are high. For LIR values that are too low,
the inductance values are high and consequently the
inductor DC resistance is also high, and therefore
inductor I2R losses are high as well. A good compromise
between size and loss is a 30% peak-to-peak ripple
current to average-current ratio (LIR = 0.3). The switching
frequency, input voltage, output voltage, and selected LIR
determine the inductor value as follows:
2
0.33
1
t
≅ (
+
)
RESPONSE
f
f
SW
C
where I
is the load current step, t
is the
is the allowable
STEP
RESPONSE
response time of the controller, DV
OUT
output-voltage deviation, f is the target closed-loop
crossover frequency, and f
C
SW
is the switching frequency.
f
is generally chosen to be 1/8 to 1/10 of f
.
C
SW
Use Table 2 to select output capacitors for fixed 5V
and 3.3V output-voltage applications based on the
MAX17501E/MAX17501F.
V
×(V - V
)
OUT
× f
IN
OUT
L =
V
×I
×LIR
IN SW OUT
Table 1. Inductor Selection
V
(V)
I
(max) (mA)
500
L (µH)
47
MINIMUM I (mA)
SAT
SUGGESTED PART
Coilcraft LPS6235-473ML_
Coilcraft LPS6235-333ML_
OUT
OUT
5
800
800
3.3
500
33
���������������������������������������������������������������� Maxim Integrated Products 11
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Table 2. Output Capacitor Selection
V
(V)
I
(max) (mA)
500
TYPE
VOLTAGE RATING (V)
SUGGESTED PART
Murata GRM31CR70J106KA01L
Murata GRM31CR70J106KA01L
OUT
OUT
5
10FF/1206/X7R
10FF/1206/X7R
6.3
6.3
3.3
500
Soft-Start Capacitor Selection
Power Dissipation
The device implements adjustable soft-start operation for
the synchronous step-down converter. A capacitor con-
nected from the SS pin to GND programs the soft-start
period.
It should be ensured that the junction temperature of the
device does not exceed +125NC under the operating
conditions specified for the power supply.
At a particular operating condition, the power losses
that lead to temperature rise of the device are estimated
as follows:
The soft-start time (t ) is related to the capacitor
SS
connected at SS (C ) by the following equation:
SS
C
= 5.55× t
SS
SS
1
2
P
= P
×
-1 - I
×R
OUT DCR
)
LOSS
(
OUT
where t
is in milliseconds and C
For example, to have a 1.8ms soft-start time, a 10nF
capacitor should be connected from the SS pin to GND.
is in nanofarads.
SS
SS
η
P
= V
×I
OUT
OUT OUT
Setting the Input Undervoltage
Lockout Level
The device offers an adjustable input undervoltage-
lockout level. Set the voltage at which the device turns
where P
device, and R
Inductor (see the Typical Operating Characteristics for more
information on efficiency at typical operating conditions).
is the output power, Eis is the efficiency of the
OUT
is the DC resistance of the output
DCR
on with a resistive voltage-divider connected from V
IN
The maximum power that can be dissipated in the
device’s 10-pin TDFN-EP package is 1188.7mW at
+70NC temperature. The power dissipation capability
should be derated as the temperature goes above
+70NC at 14.9mW/NC. For a multilayer board, the thermal
performance metrics for the package are given below:
to GND (see Figure 1). Connect the center node of the
divider to EN/UVLO.
Choose R1 to be 3.3MI, and then calculate R2 as follows:
R1×1.218
R2 =
(V
-1.218)
INU
B
= 67.3NC/W
= 18.2NC/W
JA
JC
where V
to turn on.
is the voltage at which the device is required
INU
B
The junction temperature of the device can be estimated
at any given maximum ambient temperature (T
from the following equation:
)
A_MAX
V
IN
R1
T
= T
+ θ ×P
A_MAX JA LOSS
(
)
J_MAX
EN/UVLO
If the application has a thermal-management system that
ensures that the exposed pad of the device is maintained
R2
at a given temperature (T
) by using proper heat
EP_MAX
GND
sinks, then the junction temperature of the device can be
estimated at any given maximum ambient temperature
from the equation below:
Figure 1. Adjustable EN/UVLO Network
T
= T
+ θ ×P
(
)
J_MAX
EP_MAX JC LOSS
���������������������������������������������������������������� Maxim Integrated Products 12
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
When routing the circuitry around the device, the analog
small-signal ground and the power ground for switch-
ing currents must be kept separate. They should be
connected together at a point where switching activity
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 current-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.
is at minimum, typically the return terminal of the V
CC
bypass capacitor. This helps to keep the analog ground
quiet. The ground plane should be kept continuous/
unbroken as much as possible. No trace carrying high
switching current should be placed directly over any
ground plane discontinuity.
A ceramic input filter capacitor should be placed close to
PCB layout also affects the thermal performance of the
design. A number of thermal vias that connect to a large
ground plane should be provided under the exposed
pad of the device, for efficient heat dissipation. Several
vias in parallel have lower impedance than a single via.
the V pin of the device. This eliminates as much trace
inductance effects as possible and gives the device a
IN
cleaner voltage supply. The bypass capacitor for the V
CC
pin should also be placed close to the pin to reduce effects
of trace impedance. The feedback trace should be routed
as far as possible from the inductor.
For a sample layout that ensures first-pass success,
refer to the MAX17501 evaluation kit layout available at
www.maxim-ic.com.
���������������������������������������������������������������� Maxim Integrated Products 13
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Applications Circuits
L1
47µH
V
V
OUT
IN
V
LX
IN
5V, 500mA
24V 20%
C1
1µF
1206
C4
10µF, 6.3V
1206
R1
3.32MI
1
JU1 2
3
PGND
EN/UVLO
R2
866kI
MAX17501F
GND
V
CC
C2
1µF
FB
SS
C3
3300pF
N.C.
RESET
RESET
Figure 2. MAX17501F Application Circuit (5V Output, 500mA Maximum Load Current, 600kHz Switching Frequency)
L1
33µH
V
V
OUT
IN
V
LX
IN
3.3V, 500mA
24V 20%
C1
1µF
1206
C4
10µF, 6.3V
1206
R1
3.32MI
1
JU1 2
3
PGND
EN/UVLO
R2
MAX17501E
866kI
GND
V
CC
C2
1µF
FB
SS
C3
3300pF
N.C.
RESET
RESET
Figure 3. MAX17501E Application Circuit (3.3V Output, 500mA Maximum Load Current, 600kHz Switching Frequency)
���������������������������������������������������������������� Maxim Integrated Products 14
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Ordering Information/Selector Guide
OUTPUT
VOLTAGE
SWITCHING
FREQUENCY
PEAK-CURRENT-MODE
CONTROL SCHEME
OUTPUT
CURRENT
PART
PIN-PACKAGE
MAX17501EATB+
MAX17501FATB+
10 TDFN-EP*
10 TDFN-EP*
3.3V
5V
600kHz
600kHz
Forced PWM
Forced PWM
500mA
500mA
Note: All devices are specified over the -40°C to +125°C operating temperature range. Optional variants available to support
adjustable output and PFM. Contact your Maxim sales representative for more information.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Chip Information
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.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.
PROCESS: BiCMOS
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
10 TDFN-EP
T1032N+1
21-0429
90-0082
���������������������������������������������������������������� Maxim Integrated Products 15
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
5/12
Initial release
—
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim 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 Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
16
©
2012 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
相关型号：
MAX17502EATB+T
Switching Regulator/Controller, Current-mode, 1A, 640kHz Switching Freq-Max, BICMOS, PDSO10,
MAXIM
MAX17502GATB+T
Switching Regulator/Controller, Current-mode, 1A, 640kHz Switching Freq-Max, BICMOS, PDSO10,
MAXIM
©2020 ICPDF网 联系我们和版权申明