MAX20004EAFOBVY_技术文档

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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

CONTROL LOGIC

BIAS

∑

PWM

COMP

PGND

V_REF

ERROR

AMP

FPWM CLK

SOFT-START

GENERATOR

PGOOD

COMP

ZX

COMP

PGND

OUT

FB

POK

FEEDBACK

SELECT

CLK

SYNC

OTP

TRIMBITS

V_REF

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

= 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

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

= 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

BIAS

10mA, BIAS not switched over to V

OUT

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

Thermal Shutdown

Hysteresis

OUTPUT VOLTAGE

PWM-Mode Output

Voltage

V

6V < V

< 36V, no load, PWM

3.23

3.82

4.9

3.3

3.9

5

3.37

3.4

V

OUT_3.3V

SUP

SKIP-Mode Output

Voltage

V

< 36V, no load, FB = BIAS

SKIP_3.3V

PWM-Mode Output

Voltage

V

6V < V

< 36V, no load, PWM

3.98

4.02

5.1

OUT_3.9V

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

< 36V, no load, PWM

OUT_5V

SUP

SKIP-Mode Output

Voltage

V

< 36V, no load, FB = BIAS

4.9

5

5.15

SKIP_5V

Load Regulation

Line Regulation

V

= V

30mA < I

< I

MAX

0.2

0.02

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 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,

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

= 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

= 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

= 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

SS_HI

SYNC, SSEN Low

Threshold

V

0.4

1

SS_LO

SYNC, SSEN Leakage

Current

I

T

= +25°C

0.1

μA

SS

A

EN High Threshold

EN Low Threshold

EN Hysteresis

EN Leakage Current

RESET

V

2.4

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

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

8

PGND

6

5

7

F173A3FY+7

(3.5mm x 3.75mm)

Pin Description

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)

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

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

= 2.1MHz

= 400kHz

4

6

8

4

6

8

1.5

1

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

× 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

=

OUT

I

STEP

2

I

× L

I

× t

STEP

2 × (V − V ) × D

STEP DELAY

C

≥

+

OUT

× ΔV

ΔV

(

)

IN

OUT

MAX

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

www.maximintegrated.com

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

= 2.1MHz

= 400kHz

4

6

8

5

28

32

30

24

22

28

40

56

60

70

SW

3.3

5

3.3/3.9

36

50

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

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

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.

www.maximintegrated.com

Maxim Integrated | 18

MAX20004E/MAX20006E/

MAX20008E

Automotive, 36V, 4A/6A/8A Integrated Step-Down

Converters with Integrated Compensation

VIN

EP

CBP

CIN

LX

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

5

4

6

8

2100

400

5

10

209

233

185

173

161

3.3

5

Both

3.3

3.9

3.3

5

FPWM Only

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.


型号：	MAX20004EAFOBVY
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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