MAX20058ATCAVY [MAXIM]
60V, 1A, Automotive Synchronous Step-Down DC-DC Converter;
| 型号： | MAX20058ATCAVY |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 60V, 1A, Automotive Synchronous Step-Down DC-DC Converter |
| 文件： | 总17页 (文件大小：713K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
General Description
Benefits and Features
● Synchronous DC-DC Converters with Integrated FETs
• 60V Input for 14V and 24V Systems
• Internal Compensation
The MAX20058 is a high-efficiency, high-voltage, syn-
chronous step-down DC-DC converter IC with integrated
MOSFETs that operates over a 4.5V to 60V input. The
converters can deliver up to 1A current. Output voltage is
programmable from 0.8V to 90%V . The feedback volt-
age-regulation accuracy over -40°C to +125°C is ±1.5%.
● Flexibility
IN
• Output Adjustable from 0.8V to 90%V
• 200kHz to 2200kHz Adjustable Frequency with
External Clock Synchronization
IN
The IC features a peak-current-mode-control architecture
and can be operated in the pulse-width modulation (PWM)
or pulse-frequency modulation (PFM) control schemes.
• Programmable Peak Current Limit (1.14A or 1.6A)
●
RESET Output and EN Input (26V max) Simplify
Power Sequencing
The MAX20058 is available in a 12-pin (3mm x 3mm)
side-wettable TDFN package with an exposed pad for
thermal heat dissipation.
● Protection Features and Operating Range Ideal for
Automotive Applications
• Programmable EN/UVLO Threshold
• Adjustable Soft-Start and Prebiased Power-Up
• Thermal Shutdown
• -40°C to +125°C Automotive Temperature Range
• AEC-Q100 Qualified
Applications
● 14V/24V Systems
● Truck Applications
Ordering Information appears at end of data sheet.
19-100263; Rev 2; 5/19
MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Absolute Maximum Ratings
V
to SGND .........................................................-0.3V to +65V
Continuous Power Dissipation
IN
EN/UVLO to SGND...............................................-0.3V to +26V
(Multilayer Board) (T = +70°C,
A
EXTVCC to SGND ................................................-0.3V to +14V
LX to PGND..................................................-0.3V to V + 0.3V
IN
FB, SS, MODE/ILIM,
derate 24.4mW/°C above +70°C)...........................1951.2mW
Operating Temperature Range......................... -40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range............................ -65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow).......................................+260°C
ESD Protection – Human Body Model................................±2kV
RT/SYNC to SGND .................................-0.3V to V
+ 0.3V
CC
PGND to SGND....................................................-0.3V to +0.3V
LX Total RMS Current ........................................................±1.2A
RESET, V
to SGND............................................-0.3V to +6V
CC
Package Information
12 SW TDFN-EP
Package Code
TD1233Y+2
21-100176
90-100072
Outline Number
Land Pattern Number
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θ
)
41°C/W
8.5°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.
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.
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Electrical Characteristics
(V = 24V, V
= unconnected, R
= 105kΩ, LX = unconnected, T = T = -40°C to +125°C, unless otherwise noted.
RT A J
IN
EN/UVLO
(Note 1)
PARAMETER
Input Voltage Range
Input Shutdown Current
SYMBOL
CONDITIONS
MIN
4.5
TYP
MAX
60
UNITS
V
V
IN
I
V
= 0V, shutdown mode
2.5
5
90
4
13
µA
IN-SH
EN
I
R
R
= open or 422kΩ
= 243kΩ or 121kΩ
µA
Q_PFM
ILIM
ILIM
Input Quiescent Current
I
3
5
mA
Q_PWM
ENABLE/UVLO (EN)
V
V
V
V
V
rising
1.19
1.09
1.215
1.115
0.7
1.24
1.14
ENR
EN/UVLO
EN/UVLO
EN/UVLO
EN/UVLO
EN Threshold
V
falling
V
ENF
V
falling, true shutdown
= 1.215V
EN-TRUESD
EN Pullup Current
I
2.2
2.5
2.8
µA
EN
LDO (V
)
CC
Output Voltage Range
Current Limit
VCC
6V < V < 60V, 0mA < I
< 5mA
4.75
12
5
5.25
52
V
mA
V
IN
VCC
I
V
V
V
V
= 4.3V, V = 12V
26
VCC-MAX
CC
IN
Dropout
V
= 4.5V, I = 5mA
VCC
0.3
CC-DO
IN
V
rising
falling
4.05
3.65
4.2
3.8
4.35
3.95
V
CC-UVR
CC
CC
UVLO
V
V
CC-UVF
EXT LDO (EXTVCC)
Switchover Threshold
EXTVCC rising
4.65
4.74
0.3
4.88
V
V
Switchover-Threshold
Hysteresis
Dropout
EXTVCC-DO
V
V
= 4.75V, I
= 5mA
0.1
34
V
EXTVCC
VCC
Current Limit
POWER MOSFETs
= 4.3V, V
= 5V
15
21
mA
CC
EXTVCC
High-Side pMOS
On-Resistance
R
I
I
= 0.3A, sourcing
0.9
1.8
Ω
DS-ONH
LX
LX
Low-Side nMOS
On-Resistance
R
= 0.3A, sinking
0.275
0.55
2
Ω
DS-ONL
T = +25°C
µA
LX Leakage Current
SOFT-START
A
Charging Current
I
4.7
5
5.3
µA
SS
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Electrical Characteristics (continued)
(V = 24V, V
= unconnected, R
= 105kΩ, LX = unconnected, T = T = -40°C to +125°C, unless otherwise noted.
IN
EN/UVLO
RT A J
(Note 1)
PARAMETER
FEEDBACK (FB)
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
R
R
= 243kΩ or 121kΩ
= open or 422kΩ
0.788
0.788
-100
0.8
0.812
0.824
100
V
V
ILIM
FB Regulation Voltage
V
FB
0.812
ILIM
FB Input Leakage Current
V
FB
= 1V, T = +25°C
nA
A
CURRENT LIMIT
R
R
R
R
R
R
R
= open or 243kW
= 121kΩ or 422kΩ
= open or 422kΩ
= 243kΩ
1.4
1.6
1.14
2.5
2.0
ILIM
ILIM
ILIM
ILIM
ILIM
ILIM
ILIM
I
SOURCE-
LIMIT
Peak Current-Limit Threshold
A
mA
A
0.94
1.36
Negative Current-Limit
Threshold
I
0.57
0.35
0.65
0.455
0.33
0.23
0.725
0.56
0.44
0.32
SINK-LIMIT
IPFM
= 121kΩ
= open
0.235
0.125
PFM Current Level
A
= 422kΩ
MODE
MODE PFM Threshold
Hysteresis
Rising
1
1.22
0.19
1.44
V
V
TIMINGS
Minimum On-Time
Maximum Duty Cycle
OSCILLATOR
t
45
89
70
93
120
97
ns
%
ON-MIN
DMAX
R
R
R
R
R
= 210kΩ
= 140kΩ
= 105kΩ
= 69.8kΩ
= 19.1kΩ
180
270
200
300
220
330
RT
RT
RT
RT
RT
kHz
Switching Frequency
f
360
400
440
SW
540
600
660
1800
1.15 x
2033
2200
1.4 x
f
SW
SYNC Input Frequency
kHz
kHz
ns
per R
f
RT
SW
SYNC Input Frequency Range
220
40
1
2200
SYNC Pulse Minimum
Off-Time
SYNC pulse must exceed this number
SYNC High Threshold
SYNC Hysteresis
V
1.22
0.18
1.44
V
V
SYNC-H
V
SYNC-HYS
Number of SYNC Pulses to
Enable Synchronization
(Note 2)
1
Cycle
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Electrical Characteristics (continued)
(V = 24V, V
= unconnected, R
= 105kΩ, LX = unconnected, T = T = -40°C to +125°C, unless otherwise noted.
IN
EN/UVLO
RT A J
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RESET
UV Threshold Rising
V
V
rising
falling
95
92
%
%
FB
FB
UV Threshold Falling
Delay after FB reaches 95%
regulation
2.1
ms
Output Low Level
I
= 1mA
0.09
1
V
RESET
Output Leakage Current
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Hysteresis
T
= +25°C
µA
A
Temperature rising (Note 2)
(Note 2)
160
20
°C
°C
Note 1: 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. Typical values are at T = +25°C.
A
Note 2: Guaranteed by design, not production tested.
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
24VIN 400kHz EFFICIENCY
vs. LOAD CURRENT
24VIN 2.2MHz EFFICIENCY
vs. LOAD CURRENT
toc01
toc02
100%
100%
90%
80%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
70%
FPWM
FPWM
60%
50%
40%
30%
20%
10%
0%
PFM
PFM
fSW = 400kHz
VIN = 24V
VOUT = 5V
fSW = 2.2MHz
VIN = 24V
VOUT = 5V
L = 33µH
L = 5.6µH
COUT = 22
µF
COUT = 22
µ
F
TA = +25°C
0.1
TA = +25°C
0.1
0.0001
0.001
0.01
1
0.0001
0.001
0.01
1
LOAD CURRENT (A)
LOAD CURRENT (A)
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
LINE REGULATION
(400kHz)
toc03
toc04
5.5
5.4
5.3
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5
25
20
15
10
5
EXTERNAL
COMPONENTS
REMOVED
PFM 1mA
V
EN = 0V
TA = +125°C
PFM 1A
FPWM 1A
PFM 500mA
FPWM 500mA
FPWM 1mA
TA = +25°C
L = 33
COUT = 22
µ
H
µF
TA = +25°C
0
10
20
30
40
50
60
22 26 30 34 38 42 46 50 54 58
VIN (V)
VIN (V)
24VIN 2.2MHz
LOAD REGULATION
24VIN 400kHz
LOAD REGULATION
toc05
toc06
5.20
5.15
5.10
5.05
5.00
4.95
4.90
5.20
5.15
5.10
5.05
5.00
4.95
4.90
VIN = 24V
L = 5.6µH
VIN = 24V
L = 33
COUT = 22
µ
H
COUT = 22µF
µF
PFM +25°C
PFM +105°C
PFM +125°C
PFM +25°C
PFM +125°C
PFM +105°C
FPWM +105°C
FPWM +25°C
FPWM +125°C
FPWM +25°C
FPWM +125°C
FPWM +105°C
0.0
0.2
0.4
0.6
0.8
1.0
0.0
0.2
0.4
0.6
0.8
1.0
LOAD (A)
LOAD (A)
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
APPLICATION OF EXTERNAL CLOCK
REMOVAL OF EXTERNAL CLOCK
5V OUTPUT, 24V INPUT
5V OUTPUT, 24V INPUT
FPWM 400kHz to 500kHz
500kHz to 400kHz FPWM
toc7
toc8
VLX
VLX
20V/div
5V/div
20V/div
5V/div
VOUT
ILX
VOUT
ILX
500mA/div
2V/div
500mA/div
2V/div
VSYNC
VSYNC
4µs
4µs
LOAD TRANSIENT
FPWM MODE
LOAD TRANSIENT
PFM MODE
(10mA to 1A PULSE)
(10mA to 1A PULSE)
toc9
toc10
VIN = 24V
VOUT = 5V
L = 33
COUT = 22
VIN = 24V
VOUT = 5V
L = 33
COUT = 22
µ
H
µ
H
µF
µF
VOUT
(AC)
VOUT
(AC)
500mV/div
500mV/div
2V/div
1A/div
2V/div
1A/div
IOUT
IOUT
VRESET
VRESET
1ms
1ms
LINE TRANSIENT
FPWM MODE
SOFT-START/SHUTDOWN FROM EN
FPWM MODE
(10mA LOAD)
(500mA LOAD)
toc11
toc12
VIN = 24V
L = 33µH
COUT = 22µF
20V/div
2V/div
VEN
VOUT
ILX
VIN
500mV/div
VOUT
5V/div
VIN = 24V
L = 33
COUT = 22
µ
H
500mA/div
µF
5V/div
VRESET
5V/div
VRESET
200µs
2ms
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
SHORT-CIRCUIT
FPWM MODE
SOFT-SHORT CIRCUIT
(VOUT FORCED TO 80% OF REGULATION)
toc13
toc14
20V/div
VLX
VOUT
ILX
20V/div
5V/div
VLX
VOUT
ILX
5V/div
1A/div
1A/div
5V/div
VRESET
5V/div
VRESET
20µs
20µs
STEADY-STATE SWITCHING WAVEFORMS
(5V OUTPUT, 1A LOAD CURRENT)
STEADY-STATE SWITCHING WAVEFORMS
(5V OUTPUT, 10mA LOAD CURRENT)
PFM MODE
FPWM MODE
toc15
toc16
VOUT
(AC)
VOUT
(AC)
20mV/div
50mV/div
20V/div
VLX
ILX
500mA/div
VLX
10V/div
1µs
40µs
SLOW INPUT VOLTAGE
(5V OUTPUT, 10mA LOAD CURRENT)
PFM MODE
toc17
20V/div
VIN
VOUT
2V/div
5V/div
VRESET
4s
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Pin Configuration
TOP VIEW
12
11 10
9
8
7
MAX20058
+
1
2
3
4
5
6
SW TDFN-EP
(3mm x 3mm)
Pin Description
PIN
NAME
FUNCTION
Power Ground Pin of the Converter. Connect externally to the power ground plane. Connect the
SGND and PGND pins together at the ground return path of the V bypass capacitor.
1
PGND
CC
Power-Supply Input. 4.5V to 60V input supply range. Decouple to PGND with a 2.2µF capacitor;
place the capacitor close to the V and PGND pins.
2
3
V
IN
IN
5V LDO Output. Bypass V
with a 1µF ceramic capacitance to SGND. This LDO is intended to
CC
V
CC
power internal circuits only.
Enable/Undervoltage Lockout Pin. Drive EN/UVLO high to enable the output. Connect to the center of
4
5
6
EN/UVLO
RESET
the resistor-divider between V and SGND to set the input voltage at which the part turns on. Leave
IN
the pin unconnected for always-on operation.
Open-Drain RESET Output. The RESET output is driven low if FB drops below 92% of its set value.
RESET goes high 2.1ms after FB rises above 95% of its set value.
Frequency-Set and Synchronization Pin. Connect a resistor from RT/SYNC to SGND to set the
switching frequency of the part between 200kHz and 2000kHz. An external clock can be connected to
the RT/SYNC pin to synchronize the part with an external frequency up to 2200kHz.
RT/SYNC
7
8
9
EXTVCC
FB
External Power-Supply Input for the Internal LDO
Feedback Input. Connect FB to the center tap of an external resistor-divider from the output to SGND
to set the output voltage.
SS
Soft-Start Input. Connect a capacitor from SS to SGND to set the soft-start time.
Mode and Current-Limit Set Pin. Connect a resistor from MODE/ILIM to SGND to program the peak
and runaway current limits and mode of operation of the part. See the Current Limit and Mode of
Operation Selection section for more details.
10
MODE/ILIM
11
12
SGND
LX
Analog Ground
Switching Node. Connect the LX pin to the switching side of the inductor.
Exposed Pad. Connect EP to the SGND pin. Connect to a large copper plane below the IC to improve
heat-dissipation capability. Add thermal vias below the exposed pad.
—
EP
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Functional Diagram
EXTVCC
V
V
IN
MAX20058
CC
INTERNAL LDO
REGULATORS
POK
VCC_INT
EN/UVLO
PEAK-LIMIT
CHIPEN
CS
CURRENT-SENSE
AMPLIFIER
CURRENT-
SENSE LOGIC
1.215V
PFM
SGND
EP
HIGH-SIDE
DRIVER
THERMAL
SHUTDOWN
DH
DL
LX
PFM/PWM
CONTROL
LOGIC
LOW-SIDE
DRIVER
CLK
RT/SYNC
OSCILLATOR
SLOPE
PGND
MODE/ILIM
MODE SELECT
SINK LIMIT
ZX/ILIMN
COMP
1.22V
SLOPE
CS
NEGATIVE
CURRENT REF
RESET
FB
SS
PWM
ERROR
AMPLIFIER
0.76V
FB
2ms
DELAY
EXTERNAL
SOFT-START
CONTROL
CLK
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
PWM Mode Operation
Detailed Description
In PWM mode, the inductor current can go negative.
PWM operation provides constant frequency operation at
all loads, and is useful in applications sensitive to switch-
ing frequency. However, the PWM mode of operation
gives lower efficiency at light loads compared to the PFM
mode of operation.
The MAX20058 high-efficiency, high-voltage, step-down
DC-DC regulator IC operates from 4.5V to 60V and deliv-
ers up to 1A load current. Feedback voltage-regulation
accuracy meets ±1.5% over load, line, and temperature.
The IC uses a peak-current-mode-control scheme. An
internal transconductance error amplifier generates 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.
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
to a fixed peak every clock cycle until the output rises to
102% of the nominal voltage by monitoring the FB pin.
Resistor tolerance will impact actual output voltage. Once
the output reaches 102% of the nominal 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% of the nominal voltage. Most of the inter-
nal blocks are turned off in hibernate operation to save
quiescent current. After the output falls below 101% of
the nominal voltage, the device comes out of hibernate
operation, turns on all internal blocks and again com-
mences the process of delivering pulses of energy to the
output until it reaches 102% of the nominal output voltage.
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 and remains on until either the next
rising edge of the clock arrives or sink current limit is
detected. The inductor releases the stored energy as its
current ramps down, and provides current to the output.
The internal low R
pMOS/nMOS switches ensure
DS(ON)
high efficiency at full load.
The IC also integrates switching-frequency selector pin,
current-limit and mode-of-operation selector pin, enable/
undervoltage lockout (EN/UVLO) pin, programmable soft-
start pin, and open-drain RESET signal.
The advantage of the PFM mode is higher efficiency at
light loads because of lower quiescent current drawn
from supply. However, the output-voltage ripple is higher
compared to PWM mode of operation and switching fre-
quency is not constant at light loads.
Current Limit and Mode of Operation
Table 1 lists the value of the resistors to program PWM or
PFM modes of operation and 1.6A or 1.14A peak current
limits.
Linear Regulator (V
)
CC
The IC has two internal low-dropout regulators (LDOs),
which power V . One LDO is powered from the input
CC
The mode of operation cannot be changed “on-the-fly”
after power-up.
voltage and the other LDO is powered from the EXTVCC
pin. Only one of the two LDOs is in operation at a time,
depending on the voltage levels present at the EXTVCC
pin.
Table 1. R
Settings
ILIM
PEAK CURRENT
LIMIT (A)
MODE OF
OPERATION
If EXTVCC rises above 4.74V (typ), V
the EXTVCC pin. If EXTVCC falls below 4.44V (typ), V
is powered from the input voltage. Powering V
is powered from
R
(kΩ)
CC
ILIM
CC
Open
1.6
1.14
1.6
PFM
PFM
PWM
PWM
from
CC
EXTVCC increases efficiency, particularly at higher input
voltages. Typical V output voltage is 5V. Bypass V
422
243
121
CC
CC
to SGND with a 1μF capacitor.
1.14
When V falls below its undervoltage lockout (3.8V,
CC
typ), the internal step-down controller is turned off, and
LX switching is disabled. The LX switching is enabled
again when the V
voltage exceeds 4.2V (typ). The
CC
400mV (typ) hysteresis prevents chattering on power-up
and power-down.
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
When powering EXTVCC from V
, a R-C network
Table 2. RT/SYNC Resistor Settings
OUT
should be placed in the path to protect the LDO from a
potential negative voltage transient due to a short circuit
event. A 4.7Ω resistor and a 0.1μF capacitor is recom-
mended (see Typical Application Circuit on page 15).
RT/SYNC RESISTOR
SWITCHING FREQUENCY
(kHz)
VALUE (kΩ)
210
140
105
69.8
19.1
200
300
400
600
2000
Switching-Frequency Selection and External
Frequency Synchronization
The RT/SYNC pin programs the switching frequency of
the converter. Connect a resistor from RT/SYNC to SGND
to set the switching frequency of the part at any one of five
discrete frequencies: 200kHz, 300kHz, 400kHz, 600kHz,
or 2MHz (see Table 2 for resistor values).
Overcurrent Protection
The IC is provided with a robust overcurrent-protection
scheme that protects the device under overload and
output short-circuit conditions. The positive current limit
is triggered when the peak value of the inductor current
hits a fixed threshold (ILIM_P, 1.6A/1.14A). At this point,
the high-side switch is turned off and the low-side switch
turned on. The low-side switch is kept on until the inductor
current discharges below 0.7 x ILIM_P.
The internal oscillator of the device can be synchro-
nized to an external clock signal on the RT/SYNC pin.
The external synchronization clock frequency must be
between 1.15 x f
and 1.4 x f , where f
is the
SW
SW
SW
frequency programmed by the resistor connected from
the RT/SYNC pin. The MAX20058 have been tested up
to 2000kHz with a 19.1kΩ resistor.
Operating Input Voltage Range
While in PWM mode of operation, the negative current
limit is triggered when the valley value of the inductor
current hits a fixed threshold (ILIM_N, -0.65A/-0.455A,
depending on the value of the resistor connected to the
MODE/ILIM pin). At this point, the low-side switch is
turned off and the high-side switch is turned on.
The minimum and maximum operating input voltages for
a given output voltage should be calculated as shown in
the following equation.
Equation 1:
V
+ I
× (R
+ 0.55)
(
)
OUT
OUT(MAX)
DCR
RESET Output
V
=
+ I
(
×1.25
OUT(MAX)
)
IN(MIN)
D
MAX
The IC includes a RESET pin to monitor the output volt-
age. The open-drain RESET output requires an external
pullup resistor. RESET goes high (high impedance) in
2.1ms after the output voltage increases above 95% of
the nominal voltage. RESET goes low when the output
voltage drops to below 92% of the nominal voltage.
RESET also goes low during thermal shutdown.
V
OUT
× t
ON(MIN)
V
=
IN(MAX)
f
SW(MAX)
where V
is the steady-state output voltage, I
OUT(MAX)
OUT
is the maximum load current, R
of the inductor, D
is the DC resistance
DCR
is the maximum allowable duty ratio
is the maximum switching frequency,
MAX
(0.89), f
SW(MAX)
and t
(120ns).
is the worst-case minimum switch on-time
ON(MIN)
Thermal-Shutdown Protection
The IC features thermal-overload protection and turns
off when the junction temperature exceeds +160°C (typ).
Once the device cools by 20°C (typ), it turns back on with
a soft-start sequence.
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
where:
and:
Applications Information
(V − V
)× V
OUT
×L
IN
OUT
∆I
=
P−P
Inductor Selection
V
× f
IN SW
Three key inductor parameters must be specified for
operation with the device: inductance value (L), inductor
saturation current (ISAT) and DC resistance (RDCR). To
select inductor value, the ratio of inductor peak-to-peak
AC current to DC average current (LIR) must be selected
first. 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 then determine the inductor
value as follows:
V
OUT
D =
V
IN
where I
is the output current, D is the duty cycle,
is the switching frequency. Use additional input
OUT
and f
SW
capacitance at lower input voltages to avoid possible
undershoot below the UVLO threshold during transient
loading.
(V –V
) x V
OUT
IN
OUT
OUT
Output Capacitor
L =
V
× f
×I
×LIR
IN
SW
For optimal phase margin, a 22μF output capacitor is
recommended. Additional output capacitance may be
needed based on application-specific output-voltage-
ripple requirements. If the total output capacitance
required is > 70μF, contact the factory for an optimized
solution.
where V
, I
, and f
are nominal values.
OUT OUT
SW
Select a low-loss inductor closest to the calculated value
with acceptable dimensions and the lowest possible DC
resistance. The saturation current rating (ISAT) of the
inductor must be high enough to ensure that saturation
occurs only above the peak current-limit value.
The allowable output-voltage ripple and the maximum
deviation of the output voltage during step-load currents
determine the output capacitance and its ESR.
Input Capacitor Selection
A low-ESR ceramic input capacitor of 4.7μF is recommend-
ed for proper device operation. This value can be adjusted
based on application input-voltage-ripple requirements.
V
Ripple Requirement
OUT
The output ripple comprises ΔV (caused by the capacitor
Q
discharge) and ΔV
(caused by the ESR of the output
ESR
The discontinuous input current of the buck converter
causes large input ripple current. The switching frequen-
cy, peak inductor current, and the allowable peak-to-peak
input-voltage ripple dictate the input-capacitance require-
ment. Increasing the switching frequency or the inductor
value lowers the peak-to-average current ratio, yielding a
lower input-capacitance requirement.
capacitor). Use low-ESR ceramic or aluminum electrolytic
capacitors at the output. For aluminum electrolytic capaci-
tors, the entire output ripple is contributed by ΔV
. Use
ESR
Equation 4 to calculate the ESR requirement and choose
the capacitor accordingly. If using ceramic capacitors,
assume the contribution to the output ripple voltage from
the ESR and the capacitor discharge to be equal. The fol-
lowing equations show the output capacitance and ESR
requirement for a specified output-voltage ripple.
The input ripple comprises of ΔV (caused by the capaci-
Q
tor discharge) and ΔV
(caused by the ESR of the
ESR
input capacitor). The total voltage ripple is the sum of ΔV
Equation 4:
Q
and ΔV
. Assume that input-voltage ripple from the
ESR
∆V
ESR
ESR and the capacitor discharge is equal to 50% each.
The following equations show the ESR and capacitor
requirement for a target voltage ripple at the input:
ESR =
∆I
P−P
∆I
P−P
C
=
OUT
Equation 3:
8× ∆V × f
Q
SW
∆V
+ (∆I
ESR
/ 2)
P−P
ESR =
I
OUT
I
×D(1− D)
OUT
C
=
IN
∆V × f
Q
SW
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
where:
(C
) and the output voltage (V ) determine the mini-
SEL OUT
mum required soft-start capacitor as shown below.
(V − V
)× V
OUT
×L
IN
OUT
∆I
=
P−P
V
× f
Equation 6:
IN SW
V
= ∆V
+ ∆V
Q
C
≥ 30 x 10-6 x C
x V
SEL OUT
SS
OUT_RIPPLE
ESR
The soft-start time (t ) is related to the capacitor con-
SS
ΔI
is the peak-to-peak inductor current as calculated
P-P
nected at SS (C ) by the following equation.
SS
above, and f
is the converter’s switching frequency.
SW
Equation 7:
Transient Response Requirement
C
SS
The allowable deviation of the output voltage during fast-
transient loads also determines the output capacitance
and its ESR. The output capacitor supplies the step-load
current until the converter responds with a greater duty
t
=
SS
−6
6.25×10
For example, to program a 2ms soft-start time, a 12nF
capacitor should be connected from the SS pin to SGND.
cycle. The response time (t
) depends on the
RESPONSE
closed-loop bandwidth of the converter. The high switch-
ing frequency of the devices allows for a higher closed-
Adjusting the Output Voltage
Set the output voltage with resistive voltage-dividers con-
nected from the positive terminal of the output capacitor
loop bandwidth, thus reducing t
and the out-
RESPONSE
put-capacitance requirement. The resistive drop across
the output capacitor’s ESR and the capacitor discharge
causes a voltage droop during a step load. Keep the
maximum output-voltage deviations below the tolerable
limits of the electronics being powered. When using a
ceramic capacitor, assume an 80% and 20% contribution
from the output-capacitance discharge and the ESR drop,
respectively. Use the following equations to calculate the
required ESR and capacitance value:
(V
) to SGND (Figure 1). Connect the center node of
OUT
the divider to the FB pin. To optimize efficiency and output
accuracy, use the following calculations to choose the
resistive divider values.
Equation 8:
15× V
OUT
R4 =
0.8
R4× 0.8
− 0.8)
R5 =
Equation 5:
(V
OUT
∆V
where R4 and R5 are in kΩ.
ESR
ESR
I
=
OUT
I
STEP
× t
STEP
RESPONSE
C
=
OUT
2× ∆V
V
Q
OUT
R4
R5
where I
response time of the converter.
is the load step and t
is the
STEP
RESPONSE
FB
Soft-Start Capacitor Selection
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 for the corre-
sponding output voltage. The selected output capacitance
Figure 1. Setting the Output Voltage
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
should be routed away from the inductor.
Series R-C Selection
To achieve higher bandwidth, connect an R-C series circuit
across the bottom feedback resistor (see Figure 2).
2) Solder the exposed pad to a large copper-plane area
under the device. To effectively use this copper area
as heat exchanger between the PCB and ambient,
expose the copper area on the top and bottom side.
Add a few small vias or one large via on the copper
pad for efficient heat transfer. Connect the exposed
pad to PGND, ideally at the return terminal of the
output capacitor.
Select the R-C (R6 and C6) values using Equations 9
and 10.
Equation 9:
R4×R5
R4 + R5 1− 0.99k
k
R6 =
×
6
1.125×10
3) Isolate the power components and high-current
paths from sensitive analog circuitry.
C6 =
k
f
×R6×
C
2
4) Keep the high-current paths short, especially at
the ground terminals. This practice is essential for
stable, jitter-free operation.
1− k
where:
And C
R4
R5
5) Connect PGND and SGND together, preferably at
the return terminal of the input capacitor. Do not con-
nect them anywhere else.
f
× C
× 1+
C
OUT
k =
3.6274
6) Keep the power traces and load connections short.
This practice is essential for high efficiency. Use
thick copper PCB to enhance full-load efficiency and
power-dissipation capability.
is the derated capacitance value for a given
OUT
bias voltage in µF, f is the targeted crossover frequency
in Hz, (15kHz or 1/20th of f ; whichever is lower) R4
and R5 are the feedback network in kΩ, R6 is in kΩ, and
C6 is in nF.
C
SW
7) Route high-speed switching nodes away from sensi-
tive analog areas. Use internal PCB layers as PGND
to act as EMI shields to keep radiated noise away
from the device and analog bypass capacitor.
Setting the Undervoltage Lockout
Drive EN/UVLO high to enable the output. Leave the pin
unconnected for always-on operation. Set the voltage at
which each converter turns on with a resistive voltage-
V
OUT
divider connected from V to SGND (see Figure 3).
IN
R4
Connect the center node of the divider to EN/UVLO pin.
FB
Equation 10 (choose R1 as follows):
R6
R1 ≤ (110000 x V
)
INU
R5
where V
is the input voltage at which the device is
INU
C6
required to turn on and R1 is in Ω. Calculate the value of
SGND
R2 as shown in Equation 11.
Equation 11:
Figure 2. R-C Network for Increased Phase Margin
1.215×R1
R2 =
V
−1.215 + (2.5µA ×R1)
(
)
INU
V
IN
PCB Layout Guidelines
R1
R2
Careful PCB layout is critical to achieve low switching
power losses and clean, stable operation. Use a multi-
layer board wherever possible for better noise immunity.
Follow the guidelines below for a good PCB layout:
EN/UVLO
1) Place the input capacitor right next to the V pin.
IN
The bypass capacitor for the V
pin should be as
CC
Figure 3. Undervoltage-Lockout Divider
close as possible to the pin. The feedback trace
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Typical Application Circuit
V
OUT
L1
5V, 1A
V
IN
LX
V
IN
33µH
MAX20058
C4
R4
95.3kΩ
22µF
C1
2.2µF
EN/UVLO
MODE/ILIM
FB
V
CC
PGND
R6
C2
16.9kΩ
1µF
R5
18.2kΩ
C6
4.7nF
SGND
RT/SYNC
SS
R1
105kΩ
RESET
C3
12nF
4.7Ω
V
OUT
EXTVCC
0.1µF
CIRCUIT FOR 5V OUTPUT, f = 400kHz
SW
(PFM MODE, 1.6 A CURRENT LIMIT)
Chip Information
PROCESS: CMOS
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX20058ATCA/VY+ -40°C to +125°C 12 SW TDFN-EP*
/V Denotes an automotive-qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
SW = Side-wettable package.
*EP = Exposed pad.
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MAX20058
60V, 1A, Automotive Synchronous
Step-Down DC-DC Converter
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
3/18
Initial release
—
Updated Output Voltage Range and last row in Switching Frequency rows in
Electrical Characteristics table; replaced TOC04 and updated TOC12 in Typical
Operating Characteristics section; updated Switching-Frequency Selection and
External Frequency Synchronization section and the last row in Table 2
1
2
6/18
4/19
3, 4, 6, 7, 12
2, 14, 15
Updated Absolute Maximum Rating, Equation 6 and Series R-C Selection section
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.
2019 Maxim Integrated Products, Inc.
│ 17
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