MAX20006E [MAXIM]
Automotive, 36V, 4A/6A/8A Integrated Step- Down Converters with Integrated Compensation;型号: | MAX20006E |
厂家: | MAXIM INTEGRATED PRODUCTS |
描述: | Automotive, 36V, 4A/6A/8A Integrated Step- Down Converters with Integrated Compensation |
文件: | 总21页 (文件大小:749K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
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MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-
Down Converters with Integrated
Compensation
General Description
Benefits and Features
The MAX20004E/MAX20006E/MAX20008E are small,
synchronous buck converters with integrated high-side
and low-side MOSFETs. The device family can deliver
up to 8A with input voltages from 3.5V to 36V, while
using only 15μA quiescent current at no load (except for
MAX20006EAFOD/VY+ which has FPWM mode only).
Voltage quality can be monitored by observing the RESET
signal. The devices can operate in dropout by running at
98% duty cycle, making them ideal for automotive applica-
tions.
● Multiple Functions for Small Size
• Operating V Range of 3V to 36V
IN
• 15μA Quiescent Current in Skip Mode
• Synchronous DC-DC Converter with Integrated
FETs
• 400kHz or 2.1MHz Switching Frequency
• Fixed 5ms(default) Internal Soft-Start
• 3.3V/3.9V/5.0V Fixed Output Options
• 98% Duty-Cycle Operation with Low Dropout
• RESET Output
The devices offer fixed output voltages of 5V, 3.9V, or
3.3V. Compensation is internal to the device, providing
excellent transient response. Frequency can be 400kHz
or 2.1MHz. The devices offer a forced fixed-frequency
mode and skip mode with ultra-low quiescent current of
15μA. The device has a pin-selectable (SSEN) spread-
spectrum enable to further assist systems designers with
better EMC management.
● High Precision
• ±2% Output-Voltage Accuracy
• Good Load-Transient Performance
● Robust for the Automotive Environment
• Current-Mode, Forced-PWM, and Skip Operation
• Overtemperature and Short-Circuit Protection
• 3.5mm x 3.75mm 17-Pin FC2QFN
• Symmetrical Pinout with Pin-Selectable Spread
Spectrum for Optimized EMI Performance
• -40°C to +150°C Junction Operating Range
• 40V Load-Dump Tolerant
The MAX20004E/MAX20006E/MAX20008E are available
in a small 3.5mm x 3.75mm 17-pin FC2QFN package and
use very few external components.
• AEC-Q100 Qualified
Applications
● Point-of-Load Applications in Automotive
● Distributed DC Power Systems
Ordering Information appears at end of datasheet.
● Navigation and Radio Head Units
19-100562; Rev 6; 7/20
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Simplified Block Diagram
MAX20004E/
MAX20006E/
MAX20008E
CURRENT-SENSE
AMP
SUPSW
SKIP CURRENT
COMP
BST
CLK
PEAK CURRENT
COMP
RAMP
GENERATOR
LX
LX
CONTROL LOGIC
BIAS
∑
PWM
COMP
PGND
VREF
ERROR
AMP
FPWM CLK
SOFT-START
GENERATOR
PGOOD
COMP
ZX
COMP
PGND
OUT
FB
POK
FEEDBACK
SELECT
CLK
SYNC
OTP
TRIMBITS
VREF
SUP
OSC
POK
BIAS LDO
SSEN
FPWM
VOLTAGE
REFERENCE
BIAS
RESET
GND
EN
MAIN
CONTROL
LOGIC
SEL
GND
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Maxim Integrated | 2
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Absolute Maximum Ratings
EN, SUPSW, SUP to PGND................................... -0.3V to +40V
LX to PGND (Note 1)................................ -0.3V to SUPSW+0.3V
SYNC, BIAS to GND ................................................ -0.3V to +6V
RESET to GND......................................................... -0.3V to +6V
GND to PGND ....................................................... -0.3V to +0.3V
SSEN, FB, OUT to GND................................ -0.3V to BIAS+0.3V
BST to LX ................................................................. -0.3V to +6V
LX Continuous RMS Current.................................................... 8A
Output Short-Circuit Duration......................................Continuous
Continuous Power Dissipation (T = +70°C)
A
17-FCQFN (derate 29.4mW/°C > 70°C)......................2553mW
Operating Temperature.......................................-40°C to +125°C
Junction Temperature.......................................................+150°C
Storage Temperature Range ..............................-65°C to +150°C
Lead Temperature Range.................................................+300°C
Soldering Temperature (reflow) ........................................+260°C
Note 1: Self-protected from transient voltages exceeding these limits in circuit under normal operation.
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.
Recommended Operating Conditions
TYPICAL
RANGE
PARAMETER
SYMBOL
CONDITION
UNIT
Ambient Temperature Range
-40 to 125
ºC
Note: These limits are not guaranteed.
Package Information
FC2QFN
Package Code
Outline Number
Land Pattern Number
F173A3FY+7
21-100383
90-100124
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θ
)
38.8°C/W
8°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.
Electrical Characteristics
(V
= V
= V
= 14V, T = -40°C to +150°C unless otherwise noted, (Note 2))
EN J
SUP
SUPSW
PARAMETER
SYMBOL
CONDITIONS
MIN
3.5
3
TYP
MAX
UNITS
36
V
SUP
,
Supply Voltage Range
Supply Current
After startup
t < 1s
V
V
SUPSW
40
33
V
OUT
= 3.3V, SKIP mode, no load
13
15
20
V
= 3.9V (MAX20006EAFOE/VY+
only), SKIP mode, no load (Note 3)
OUT
I
35
42
μA
SUP
V
OUT
= 5.0V, SKIP mode, no load
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Maxim Integrated | 3
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Electrical Characteristics (continued)
(V
= V
= V
= 14V, T = -40°C to +150°C unless otherwise noted, (Note 2))
EN J
SUP
SUPSW
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Shutdown Supply
Current
I
EN = 0V
= V
5
10
μA
SHDN
V
SUP
= 6V to 36V, I
BIAS
<
SUPSW
BIAS Regulator Voltage
V
4.7
2.7
5
5.4
V
V
BIAS
10mA, BIAS not switched over to V
OUT
V
V
rising
falling
3
3.3
BIAS Undervoltage
Lockout
BIAS
V
UVBIAS
2.5
2.95
BIAS
Thermal Shutdown
Temperature
T rising
J
175
15
°C
°C
Thermal Shutdown
Hysteresis
OUTPUT VOLTAGE
PWM-Mode Output
Voltage
V
6V < V
6V < V
< 36V, no load, PWM
3.23
3.23
3.82
3.82
4.9
3.3
3.3
3.9
3.9
5
3.37
3.4
V
V
V
V
V
V
OUT_3.3V
SUP
SUP
SKIP-Mode Output
Voltage
V
< 36V, no load, FB = BIAS
SKIP_3.3V
PWM-Mode Output
Voltage
V
6V < V
6V < V
< 36V, no load, PWM
3.98
4.02
5.1
OUT_3.9V
SUP
SUP
SKIP-Mode Output
Voltage
< 36V, no load, FB = BIAS,
V
SKIP_3.9V
(MAX20006EAFOE/VY+ only, Note 3)
PWM-Mode Output
Voltage
V
6V < V
6V < V
< 36V, no load, PWM
OUT_5V
SUP
SUP
SKIP-Mode Output
Voltage
V
< 36V, no load, FB = BIAS
4.9
5
5.15
SKIP_5V
Load Regulation
Line Regulation
V
V
= V
30mA < I
< I
MAX
0.2
0.02
1.5
1.5
7
%
%/V
mA
µA
FB
BIAS,
LOAD
= V
, 6V < V
< 36V
SUPSW
FB
BIAS
I
High-side MOSFET on, V
High-side MOSFET off, V
MAX20004E (4A)
– V = 5V
LX
BST_ON
BST
BST
BST Input Current
I
– V = 5V
LX
BST_OFF
5.25
7.5
8.75
12.5
17.5
A
LX Current Limit
I
MAX20006E (6A)
10
14
2
LX
MAX20008E (8A)
10.5
LX Rise Time
ns
%
Spread Spectrum
Spread spectrum enabled
= 5V, I = 1A
±3
High-Side Switch On-
Resistance
V
BIAS
38
1
76
5
mΩ
μA
LX
High-Side Switch
Leakage
High-side MOSFET off, V
= 36V,
= 36V,
SUPSW
V
LX
= 0V, T = +25°C
A
Low-Side Switch On-
Resistance
V
BIAS
= 5V, I = 1A
18
36
mΩ
LX
Low-Side Switch
Leakage
Low-side MOSFET off, V
= 36V, T = +25°C
SUPSW
1
5
μA
nA
V
LX
A
FB Input Current
I
T
A
= +25°C
20
100
FB
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Maxim Integrated | 4
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Electrical Characteristics (continued)
(V
= V
= V
= 14V, T = -40°C to +150°C unless otherwise noted, (Note 2))
EN J
SUP
SUPSW
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
FB connected to an external resistive
FB Regulation Voltage
V
FB
0.99
1.005
1.02
V
divider, 6V < V
< 36V
SUPSW
Transconductance (from
FB to internal COMP)
gm
50
66
90
80
μS
Minimum On-Time
t
f
= 2.1MHz
ns
%
ON_MIN
SW
Maximum Duty Cycle
DC
97
360
1.9
98
400
2.1
5
MAX
f
f
= 400kHz
= 2.1MHz
440
2.3
kHz
MHz
ms
SW
Oscillator Frequency
SW
Soft-Start Time
t
SS
SYNC, SSEN, EN
External Input Clock
Acquisition Time
t
1
Cycles
SYNC
f
f
= 400kHz
= 2.1MHz
300
1.8
1200
2.6
kHz
External Input Clock
Frequency
SW
MHz
SW
SYNC, SSEN High
Threshold
V
1.4
V
V
SS_HI
SYNC, SSEN Low
Threshold
V
0.4
1
SS_LO
SYNC, SSEN Leakage
Current
I
T
T
= +25°C
= +25°C
0.1
μA
SS
A
EN High Threshold
EN Low Threshold
EN Hysteresis
EN Leakage Current
RESET
V
2.4
V
V
EN_HI
V
0.6
1
EN_LO
V
0.2
0.1
V
EN_HYS
I
μA
EN
A
UV Hysteresis
UV Threshold
3
%
%
Falling
86
88
90
Hold Time
10
ms
μs
UV Debounce Time
25
Rising
Falling
104
107
105
110
OV Protection Threshold
%
Leakage Current
Output Low Level
V
in regulation, T = +25°C
A
1
μA
V
OUT
I
= 5mA
0.4
SINK
Note 2: The device is designed for continuous operation up to T = +125°C for 95,000 hours and T = +150°C for 5,000 hours.
J
J
Note 3: The MAX20006EAFOD/VY+ does not support skip mode operation and is FPWM mode only
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Maxim Integrated | 5
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Typical Operating Characteristics
((V
= V
= +14V, T = +25°C, unless otherwise noted.))
EN A
SUP
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Maxim Integrated | 6
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Typical Operating Characteristics (continued)
((V
= V
= +14V, T = +25°C, unless otherwise noted.))
EN A
SUP
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Maxim Integrated | 7
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Pin Configuration
F173A3FY+7
TOP VIEW
16
15
14
13
12
17
1
11 EN
10 SUP
SUPSW
RESET
BST
EP
2
SUPSW
3
4
9
PGND
PGND
8
PGND
PGND
6
5
7
F173A3FY+7
(3.5mm x 3.75mm)
Pin Description
PIN
1
NAME
FUNCTION
RESET
BST
Open-Drain RESET Output. To obtain a logic signal, pull RESET up with an external resistor.
High-Side Driver Supply. Connect a 0.1μF capacitor between LX and BST for proper operation.
Supply Input
2
3
SUPSW
PGND
4, 5
Power Ground. Connect all PGND pins together.
Inductor Connection. Connect LX to the switched side of the inductor. Connect all LX pins
together.
6
LX
7, 8
PGND
Power Ground. Connect all PGND pins together.
Internal High-Side Switch Supply Input. SUPSW provides power to the internal switch. Bypass
SUPSW to PGND with 0.1μF and 4.7μF ceramic capacitors. Place the 0.1μF as close to the
SUPSW and PGND pins as possible, followed by the 4.7μF capacitor.
9
SUPSW
Voltage Supply Input. SUP powers up the internal linear regulator. SUP is fused directly to
SUPSW, so it must be connected directly to SUPSW as close to the IC as possible.
10
11
SUP
EN
SUP Voltage-Compatible Enable Input. Drive EN low to disable the devices. Drive EN high to
enable the devices.
Synchronization Input. Connect SYNC to GND to enable skip-mode operation under light loads.
Connect SYNC to BIAS or an external clock to enable fixed-frequency forced-PWM-mode
operation. When driving SYNC externally do not exceed the BIAS voltage. The BIAS pin may
transition from 5V to the output voltage after startup to increase efficiency. For MAX20006EAFOD/
VY+, do not ground SYNC pin, as the part only supports FPWM mode.
12
13
SYNC
BIAS
Linear Regulator Output. BIAS powers up the internal circuitry. Bypass with a minimum 2.2μF
ceramic capacitor to ground.
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Maxim Integrated | 8
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Pin Description (continued)
PIN
14
NAME
GND
FUNCTION
Analog Ground.
15
SSEN
Spread Spectrum Enable Input. Connect to BIAS to enable spread spectrum.
Feedback Input. Connect a resistor-divider from OUT to FB to GND to set the output voltage.
Connect FB to BIAS to select a 3.3V, 3.9V, or 5V fixed output voltage (P/N dependent).
16
17
EP
FB
Switching Regulator Output. OUT also provides power to the internal circuitry when the output
voltage of the converter is set between 3V and 5V during standby mode.
OUT
Exposed pad on the internal high-side switch supply input. Connect to SUPSW pins 3 and 9 on the
PCB.
SUPSW
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Maxim Integrated | 9
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Detailed Description
The MAX20004E/MAX20006E/MAX20008E are 4A, 6A, and 8A current-mode step-down converters, respectively, with
integrated high-side and low-side MOSFETs with integrated programmable compensation. The low-side MOSFET
enables fixed-frequency FPWM operation in light-load applications. The devices operate at 3.5V (3V after start-up) to
36V input voltages, while using only 15μA (typ) quiescent current at no load (except for MAX20006EAFOD/VY+ which is
FPWM mode only). The switching frequency is factory-selectable between 400kHz and 2.1MHz and can be synchronized
to an external clock. The devices’ output voltage is available as fixed 5V, 3.9V or 3.3V, or adjustable between 1V and 5V.
The wide input voltage range, along with the ability to operate at 99% duty cycle during undervoltage transients, make
these devices ideal for automotive applications.
In light-load applications, a logic input (SYNC) allows the devices to operate either in skip mode for reduced current
consumption, or fixed-frequency FPWM mode to eliminate frequency variation and help minimize EMI. Protection
features include cycle-by-cycle current limit and thermal shutdown with automatic recovery.
MAXQ Power Architecture (No Wasted Performance)
The MAXQ power architecture allows the device to achieve the maximum dynamic performance under all worst-case
conditions. Without the MAXQ power architecture, typical AC performance would have to be reduced below the device
capabilities to guarantee that the device would be stable under all worst-case application conditions. The MAXQ power
architecture prevents this wasted capability by keeping the device operating at peak performance.
Thermal Considerations
The devices are available in 4A, 6A, or 8A versions; however, the average output-current capability is dependent on
several factors. Some of the key factors include the maximum ambient temperature (TA
), switching frequency
(MAX)
(f ), and the number of layers and the size of the PCB. See the Typical Operating Characteristics for a guideline.
SW
Wide Input Voltage Range
The device is specified to operate over a wide 3V to 36V input voltage range. Conditions such as cold crank can cause
the voltage at the SUP and SUPSW pins to drop below the programmed output voltage. Under such conditions, the
devices operate in a high duty-cycle mode (dropout mode) and continuously attempt to turn on the HSFET to facilitate
minimum dropout from input to output. To maintain gate charge on the HSFET, the BST capacitor must be periodically
recharged. To ensure proper charge on the BST capacitor when in dropout, the HSFET is turned off every 13.5μs and
the LSFET is turned on for approximately 150ns. This gives an effective duty cycle of greater than 98% in dropout.
For high input voltages, the required duty cycle to regulate its output may be smaller than the minimum on-time (80ns,
max). In this event, the device is forced to lower its switching frequency by skipping pulses.
Maximum Duty-Cycle Operation
The device has a maximum duty cycle of 98% (typ). The IC continuously monitors the time between low-side FET
switching cycles in both PWM and skip modes. Whenever the low-side FET has not switched for more than 13.5µs (typ),
the low-side FET is forced on for 150ns (typ) to refresh the BST capacitor. The input voltage at which the device enters
dropout changes depending on the input voltage, output voltage, switching frequency, load current, and the efficiency of
the design. The input voltage at which the device enters dropout can be approximated as follows:
V
OUT
V
=
+ I
× R
OUT HS
SUP
0.98
where R
is the high-side switch on-resistance, which should also include the inductor DC resistance for better
HS
accuracy.
Linear Regulator Output (BIAS)
The devices include a 5V linear regulator (V
) that provides power to the internal circuit blocks. Connect a 2.2μF
BIAS
ceramic capacitor from BIAS to GND. Under certain conditions, the BIAS regulator turns off and the BIAS pin switches to
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Maxim Integrated | 10
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
OUT (i.e., switches over) after startup to increase efficiency. For IC versions that are factory trimmed for 3.3V/3.9V fixed
output, BIAS switches to OUT under light-load conditions in skip mode only. For IC versions that are factory trimmed for
5V fixed output, the BIAS pin switches to OUT after startup regardless of load or skip/PWM mode. In any case, BIAS only
switches over if OUT is between 2.8V and 5V. In summary, BIAS can transition from 5V to V
on load, mode, and IC version.
after startup depending
OUT
Soft-Start
The devices include a fixed internal soft-start with factory-selectable options of 5ms and 10ms. Soft-start limits startup
inrush current by forcing the output voltage to ramp up towards its regulation point.
RESET Output
The devices feature an open-drain reset output (RESET). RESET asserts when V
drops below the specified falling
OUT
threshold. RESET deasserts when V
rises above the specified rising threshold after the specified hold time. Connect
OUT
RESET to the output, bias, or I/O voltage of choice with a pullup resistor.
Synchronization Input (SYNC)
SYNC is a logic-level input used for operating-mode selection and frequency control. Connecting SYNC to BIAS or to
an external clock enables forced fixed-frequency (FPWM) operation. Connecting SYNC to GND enables automatic skip-
mode operation for high light-load efficiency (except for MAX20006EAFOD/VY+ which is FPWM mode only). The IC
synchronizes to an external clock frequency at SYNC in two cycles and runs in FPWM mode when the external frequency
is within the range specified in the Electrical Characteristics Table. When the external clock signal at SYNC is absent for
more than two clock cycles, the devices use the internal clock.
System Enable (EN)
An enable control input (EN) activates the devices from their low-power shutdown mode. EN is compatible with inputs
from automotive battery level down to 3V. EN turns on the internal linear (BIAS) regulator. Once V
is above the
BIAS
internal lockout threshold (V
= 3V (typ)), the converter activates and the output voltage ramps up with the
UVBIAS
programmed soft-start time. A logic-low at EN shuts down the device. During shutdown, the BIAS regulator and gate
drivers turn off. Shutdown is the lowest power state and reduces the quiescent current to 5μA (typ). Drive EN high to
bring the device out of shutdown.
Spread-Spectrum Option
Each device has an optional spread spectrum enabled by the SSEN pin. When the SSEN pin is pulled high, the operating
frequency is varied ±3% centered on the internal switching frequency (f ). The modulation signal is a triangular wave
SW
with a frequency of 4.5kHz at 2.1MHz. For operation at f
= 400kHz, the modulation signal scales proportionally (i.e.,
SW
the modulation frequency reduces by 0.4MHz/2.1MHz). The internal spread spectrum is disabled if the devices are
synchronized to an external clock. However, the devices do not filter the input clock on the SYNC pin, and pass any
modulation present (including spread spectrum), driving the external clock. Spread spectrum is offered to improve EMI
performance of the device.
Thermal Shutdown Protection
Thermal shutdown protects the device from excessive operating temperature. When the junction temperature exceeds
the specified threshold, an internal sensor shuts down the internal bias regulator and the step-down converter, allowing
the IC to cool. The sensor turns the IC on again after the junction temperature cools by the specified hysteresis.
Current Limit / Short-Circuit Protection
The devices feature a current limit that protects them against short-circuit and overload conditions at the output. In the
event of a short-circuit or overload condition, the high-side MOSFET remains on until the inductor current reaches the
specified LX current-limit threshold. The converter then turns the high-side MOSFET off and the low-side MOSFET on
to allow the inductor current to ramp down. Once the inductor current crosses below the current-limit threshold, the
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Maxim Integrated | 11
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
converter turns on the high-side MOSFET again. This cycle repeats until the short or overload condition is removed.
A hard short is detected when the output voltage falls below 50% of the target while in current limit. If this occurs, hiccup
mode activates, and the output turns off for four times the soft-start time. The output then enters soft-start and powers
back up. This repeats indefinitely while the short circuit is present. Hiccup mode is disabled during soft-start.
Overvoltage Protection
If the output voltage exceeds the OV protection rising threshold, the high-side MOSFET turns off and the low-side
MOSFET turns on. Normal operation resumes when the output voltage goes below the falling OV threshold.
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Maxim Integrated | 12
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Applications Information
Maximum Output Current
While there are device versions that supply up to 8A, there are many factors that may limit the average output current
to less than the maximum. The devices can be thermally limited based on the selected f , number of PCB layers,
SW
PCB size, and the maximum ambient temperature. See the Typical Operating Characteristics section for guidance on the
maximum average current. For a more precise value, the θ needs to be measured in the application environment.
JA
Setting the Output Voltage
Connect FB to BIAS for a fixed 5V, 3.3V, or 3.9V output voltage. To set the output to other voltages between 1V and 5V,
connect a resistor-divider from the FB output (OUT) to GND (see Figure 1). Select R
(FB to GND resistor) less than
FB2
or equal to 100kΩ. Calculate R
(OUT to FB resistor) with the following equation:
FB1
Equation 1:
V
OUT
R
= R
− 1
FB1
FB2
V
[
]
[
]
FB
where V is the feedback regulation voltage. See the Electrical Characteristics table.
FB
Add a capacitor, C
follows:
, as shown to compensate the pole formed by the divider resistance and FB pin capacitance as
FB1
Equation 2:
R
FB2
C
= 10pF ×
FB1
R
[
]
FB1
Note: Applications that use a resistor-divider to set output voltages below 4.5V should use IC versions that are
factory-trimmed for 3.3V/3.9V fixed output voltage to ensure full output current capability.
V
OUT
R
FB1
C
FB1
MAX20004E/
MAX20006E/
MAX20008E
FB
R
FB2
Figure 1. Adjustable Output Voltage Setting
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Maxim Integrated | 13
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Forced-PWM and Skip Modes
In forced-PWM (FPWM) mode, the devices switch at a constant frequency with variable on-time. In skip mode, the
converter’s switching frequency is load-dependent. At higher load current, the switching frequency becomes fixed and
operation is similar to PWM mode. Skip mode helps improve efficiency in light-load applications by allowing switching
only when the output voltage falls below a set threshold. Since the effective switching frequency is lower in skip mode at
light load, gate charge and switching losses are lower and efficiency is increased.
Load Regulation
MAX20004E/MAX20006E/MAX20008E devices are designed to have large DC gain by having an integrator at origin in
the compensation design. This gives the devices tight load regulation and only 0.2% (typ) variation in output voltage from
full load to no load (refer to the Electrical Characteristics table). The DC load regulation as a percentage of V
can
OUT
be calculated using the following equation: Equation 3: DC load reg (%) = R
x I
/ (G x R
) where R
=
CS
OUT
m
EADC
CS
Current-sense gain I
= Maximum DC output current G = Internal error amplifier gain R
= Output impedance
OUT
m
EADC
of the error amplifier Using the worst-case numbers for the above parameters gives a worst-case load regulation of 0.6%
for MAX20004E/MAX20006E/MAX20008E devices.
Inductor Selection
Three key parameters must be considered when selecting an inductor: inductance value (L), inductor saturation current
(I
), and DC resistance (R
). The devices are designed to operate with the ratio of inductor peak-to-peak AC
SAT
DCR
current to DC average current (LIR) between 15% and 30% (typ). The switching frequency, input voltage, and output
voltage then determine the inductor value as follows:
Equation 4:
V
− V
× V
(
)
SUP
× f
OUT_
OUT
× 30 %
L
=
MIN1
V
× I
SUP SW MAX
where V
and V
are typical values (so that efficiency is optimum for typical conditions) and I
is 4A for
MAX
SUP
OUT
MAX20004E, 6A for MAX20006E, and 8A for MAX20008E, and f
is the switching frequency. Note that I
is the
SW
MAX
maximum rated output current for the device, not the maximum load current in the application. The following equation
ensures that the internal compensating slope is greater than 50% of the inductor current downslope:
Equation 5:
m2
− m ≥
2
where m is the internal compensating slope and m2 is the sensed inductor current downslope as follows:
Equation 6:
V
OUT
L
m2 =
× R
CS
where R
is 0.39 for MAX20004E, 0.29 for MAX20006E, and 0.22 for MAX20008E.
CS
f
V
SW
m = 1.35 ×
×
μs 2.2MHz
Solving for L and using a 1.3x multiplier to account for tolerances in the system:
R
CS
L
= V
OUT
×
× 1.3
MIN2
2 × m
To satisfy both L
and L
, L
must be set to the larger of the two as follows:
MIN1
MIN2 MIN
L
= max L
, L
(
)
MIN
MIN1 MIN2
The maximum nominal inductor value recommended is 1.6 times the chosen value from the above formula.
L
= 2 × L
MIN
MAX
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Maxim Integrated | 14
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Select a nominal inductor value based on the following formula:
L
< L
< L
NOM MAX
MIN
The best choice of inductor is usually the standard inductor value closets to L
for a given operating frequency is provided in Table 1:
. A summary of typical inductor values
NOM
Table 1. Inductor Selection Table
FREQUENCY
I
(A)
RECOMMENDED INDUCTANCE (μH)
OUT
f
f
f
f
f
f
= 2.1MHz
= 2.1MHz
= 2.1MHz
= 400kHz
= 400kHz
= 400kHz
4
6
8
4
6
8
1.5
1
SW
SW
SW
SW
SW
SW
0.8
8.2
6.8
4.7
Input Capacitor
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.
MAX20004E/MAX20006E/MAX20008E incorporate a symmetrical pinout that can be leveraged for better EMI
performance. Connect two high-frequency 0603 or smaller capacitors on two SUP pins on either side of the package for
good EMI performance. Connect a high-quality, 4.7μF (or larger) low-ESR ceramic capacitor on the SUP pin for low-input
voltage ripple. A bulk capacitor with higher ESR (such as an electrolytic capacitor) is normally required as well to lower
the Q of the front-end circuit and provide the remaining capacitance needed to minimize input-voltage ripple.
The input capacitor RMS current requirement (I
) is defined by the following equation:
RMS
Equations 7:
V
× V
− V
(
)
OUT
SUP OUT
√
I
= I ×
RMS LOAD(MAX)
V
SUP
I
has a maximum value when the input voltage equals twice the output voltage:
RMS
V
= 2 × V
SUP
OUT
Therefore:
I
LOAD(MAX)
2
I
=
RMS
Choose an input capacitor that exhibits less than +10°C self-heating temperature rise at the RMS input current for optimal
long-term reliability.
The input-voltage ripple consists of ΔV (caused by the capacitor discharge) and ΔV
(caused by the ESR of the
Q
ESR
capacitor). Use low-ESR ceramic capacitors with high ripple-current capability at the input. Assume the contribution from
the ESR and capacitor discharge equal to 50%. Calculate the input capacitance and ESR required for a specified input-
voltage ripple using the following equations:
Equations 8:
∆ V
ESR
∆ I
ESR
=
IN
L
I
+
OUT
2
where:
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Maxim Integrated | 15
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
V
− V
× V
(
)
SUP
OUT
OUT
× L
∆ I
=
L
V
× f
SUP SW
and:
I
× D 1 − D
( )
OUT
C
=
IN
∆ V × f
Q
SW
V
OUT
D =
V
SUPSW
where: I
is the maximum output current and D is the duty cycle.
OUT
Output Capacitor
Output capacitance is selected to satisfy the output load-transient, output-voltage ripple, and closed-loop stability
requirements. During a load step, the output current changes almost instantaneously, whereas the inductor is slow to
react. During this transition time, the load-charge requirements are supplied by the output capacitor, which causes an
undershoot/overshoot in the output voltage. For a buck converter that is controlled by peak-current, as employed in
MAX20004E/MAX20006E/MAX20008E, output capacitance also affects the control-loop stability.
The output ripple comprises ΔV (caused by the capacitor discharge) and ΔV
(caused by the ESR of the output
ESR
Q
capacitor). Use low-ESR ceramic or aluminum electrolytic capacitors at the output. For aluminum electrolytic capacitors,
the entire output ripple is contributed by ΔV . Use Equation 4 to calculate the ESR requirement and choose the
ESR
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 following equations show the output capacitance and ESR requirement for a
specified output-voltage ripple.
Equation 9:
ΔV
ESR
ESR =
ΔI
p−p
ΔI
p−p
C
=
OUT
8 × ΔV × f
Q
SW
where
(V − V
) × V
IN
OUT
× f
OUT
× L
ΔI
=
p − p
V
IN SW
V
= ΔV
+ ΔV
ESR Q
OUT_RIPPLE
ΔI
is the peak-to-peak inductor current as calculated above, and f
is the converter’s switching frequency.
SW
P-P
The output capacitor supplies the step-load current until the converter responds with a greater duty cycle. The resistive
drop across the output capacitor’s ESR and the capacitor discharge causes a voltage droop during a step load. Use a
combination of low-ESR tantalum and ceramic capacitors for better transient-load and ripple/noise performance. 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:
Equation 10:
ΔV
ESR
ESR
=
OUT
I
STEP
2
I
× L
I
× t
STEP
2 × (V − V ) × D
STEP DELAY
C
≥
+
OUT
× ΔV
ΔV
(
)
IN
OUT
MAX
Q
Q
(
)
where I
is the load step and t
is the delay for the PWM mode, the worst-case delay would be (1-D) t
when
STEP
DELAY
SW
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Maxim Integrated | 16
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
the load step occurs right after a turn-on cycle. This delay is higher in Skip mode.
Based on internal-compensation design of MAX20004E/MAX20006E/MAX20008E, for optimal phase margin (> 60°, typ),
the recommended output capacitances for standard configuration are shown in Table 2. Recommended values are the
actual capacitances, after accounting for voltage derating. If a lower or higher output capacitance is required for the
application, contact the factory for an optimized solution.
Table 2. Output Capacitance Selection
PARAMETER
I
(A)
V
(V) NOMINAL OUTPUT CAPACITANCE (μF)
OUT
MINIMUM OUTPUT CAPACITANCE (μF)
OUT
f
f
f
f
f
f
f
f
= 2.1MHz
= 2.1MHz
= 2.1MHz
= 2.1MHz
= 400kHz
= 400kHz
= 400kHz
= 400kHz
4
4
6
6
6
6
8
8
5
28
32
30
24
24
22
28
40
56
60
70
SW
SW
SW
SW
SW
SW
SW
SW
3.3
5
3.3/3.9
36
50
70
70
80
5
3.3
5
3.3
Compensation Network
An optimized compensation network ensures stable operation of the closed-loop system of the power supply while
maximizing the unity gain bandwidth of the loop to meet transient requirements. MAX20004E/MAX20006E/MAX20008E
come with internal compensation, which makes the design easy and compact for the engineer. In default mode, the
compensation is optimized to be used with the recommended output capacitance as suggested in the previous sections.
Depending on the system requirements, the output capacitance required to meet system specifications may change. To
facilitate such designs, MAX20004E/MAX20006E/MAX20008E come with a highly configurable compensation network
that can be optimized to meet system needs. Trim-selectable wide range of R
value, in steps of 10kΩ, allow
COMP
flexibility in the dynamic performance of the IC. Table 3 shows some of the values of R
as a reference, and the
COMP
corresponding recommended output capacitance for the MAX20006E family with 5V
. Similar customization can be
OUT
done for different output voltages, current rating, and f
Contact the factory for any customized requirements.
SW.
Table 3. Output Capacitance Guidelines for Customized Compensation
NOMINAL RECOMMENDED
MINIMUM RECOMMENDED
APPROX.
BANDWIDTH
V
OUT
R
FREQUENCY
COMP
C
OUT
C
OUT
5V
5V
5V
5V
5V
5V
185kΩ 2.1MHz
250kΩ 2.1MHz
300kΩ 2.1MHz
209kΩ 400kHz
300kΩ 400kHz
400kΩ 400kHz
30μF
40μF
60μF
54μF
75μF
100μF
22μF
32μF
44μF
46μF
60μF
72μF
200kHz
190kHz
180kHz
55kHz
50kHz
50kHz
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching losses and clean, stable operation. Use a multilayer board
whenever possible for better noise immunity and power dissipation. Refer to Figure 2 and the following guidelines for
good PC board layout:
1. Use the correct footprint for the IC and place as many copper planes as possible under the IC footprint to insure
efficient heat transfer.
2. Place the ceramic input-bypass capacitors, C and C , as close as possible to the SUPSW and PGND pins on both
BP
IN
sides of the IC. Use low-impedance connections (no vias or other discontinuities) between the capacitors and IC pins.
C
BP
should be located closest to the IC and should have very good high-frequency performance (small package size
www.maximintegrated.com
Maxim Integrated | 17
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
and high capacitance). Use flexible terminations or other technologies instead of series capacitors for these functions
if failure modes are a concern. This will provide the best EMI rejection and minimize internal noise on the device,
which can degrade performance.
3. Place the inductor (L), output capacitors (C
), boost capacitor (C
) and BIAS capacitor (C
) in such a way
OUT
BST
BIAS
as to minimize the area enclosed by the current loops. Place the inductor (L) as close as possible to the IC LX pin
and minimize the area of the LX node. Place the output capacitors (C ) near the inductor so that the ground side
OUT
of C
is near the C ground connection to minimize the current-loop area. Place the BIAS capacitor (C
) next
BIAS
OUT
IN
to the BIAS pin.
4. Use a contiguous copper GND plane on the layer next to the IC to shield the entire circuit. GND should also be poured
around the entire circuit on the top side. Ensure that all heat-dissipating components have adequate connections
to copper for cooling. Use multiple vias to interconnect GND planes/areas for low impedance and maximum heat
dissipation. Place vias at the GND terminals of the IC and input/output/bypass capacitors. Do not separate or isolate
PGND and GND connections with separate planes or areas.
5. Place the feedback resistor-divider (if used) near the IC and route the feedback and OUT connections away from the
inductor and LX node and other noisy signals.
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Maxim Integrated | 18
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
VIN
EP
CBP
CBP
CIN
CIN
LX
COUT
COUT
VOUT
Figure 2. Simplified Layout Example
www.maximintegrated.com
Maxim Integrated | 19
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Typical Application Circuits
Typical Application Circuit for f
= 2.1MHz, I
= 6A and Fixed Output Voltage Version
OUT
SW
SUPSW
SUP
SUPSW
C
2.2µF
C
IN4
IN1
C
0.1µF
IN3
C
0.1µF
IN2
2.2µF
EN
R
20kΩ
RESET
MAX20004E
MAX20006E
MAX20008E
SSEN
OUT
BST
LX
RESET
C
BST
0.1µF
SYNC
FB
L
BIAS
C
BIAS
C
OUT
2.2µF
PGND
GND
Ordering Information
V
MAXIMUM
OUT
SOFT
(FB TIED OPERATING FREQUENCY
TO BIAS)
(V)
T
(ms)
R
COMP
(kΩ)
HOLD
PART NUMBER
Skip/FPWM Mode
START
1
3
4
CURRENT
(A)
(kHz)
2
(ms)
MAX20004EAFOA/VY+
MAX20004EAFOB/VY+
MAX20006EAFOA/VY+
MAX20006EAFOB/VY+
MAX20006EAFOD/VY+
MAX20006EAFOE/VY+*
MAX20008EAFOC/VY+
MAX20008EAFOD/VY+
Both
Both
5
4
4
6
6
6
6
8
8
2100
2100
2100
2100
2100
2100
400
5
5
5
5
5
5
5
5
10
10
10
10
10
10
10
10
209
233
185
173
173
173
161
161
3.3
5
Both
Both
3.3
3.9
3.9
3.3
5
FPWM Only
Both
Both
Both
400
Contact factory for variants with different options.
1 - 2100kHz or 400kHz
2 - 5ms or 10ms
3 - 0.2ms or 10ms
4 - 70kΩ to 1000kΩ in 10kΩ steps
/V+ Denotes Automotive Qualified Parts
+ Indicates a lead (Pb) free/RoHS compliant package
* Future product - contact factory for availability
www.maximintegrated.com
Maxim Integrated | 20
MAX20004E/MAX20006E/
MAX20008E
Automotive, 36V, 4A/6A/8A Integrated Step-Down
Converters with Integrated Compensation
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
0
6/19
Initial release
-
4, 5, 12,
17
1
2
3
7/19
8/19
10/19
Updated Electrical Characteristics, Applications Information, and Ordering Information
Updated Applications Information and Ordering Information
14, 16, 17
Remove the FC2QFN from Package Information, remove the F173A3FY+5 from Pin
Configurations, remove MAX20006EAFOC/VY+, add MAX20004EAFOB/VY+
3, 8, 17
17
Removed future-product notation from MAX20006EAFOA/VY+ and MAX20006EAFOB/VY+
in Ordering Information
4
5
6
1/20
5/20
7/20
8, 9, 17,
19
Updated Pin Configurations, Pin Descriptions, and Applications Information
Updated General Description, Electrical Characteristics, Pin Descriptions, Detailed
Description, Typical Application Circuits, and Ordering Information
1, 3, 4, 8,
10, 20
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.
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