MAX16956AUBA+_技术文档

EVALUATION KIT AVAILABLE

MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

General Description

Features

The MAX16956 is a small, synchronous buck converter

with integrated high-side and low-side switches. The

device is designed to deliver up to 300mA with input

voltages from 3.5V to 36V, while using only 1.1µA

quiescent current at no load (fixed-output versions).

Voltage quality can be monitored by observing the

RESET signal. The device can operate near dropout by

running at 97% duty cycle, making it ideal for automotive

applications under cold-crank.

● Operating V Range: 3.5V to 36V (42V Tolerant)

IN

● DC-DC Converter Up to 300mA Capability

● 1.1µA Quiescent Current in Standby Mode

(Fixed-Output-Voltage Versions Only)

● 2.1MHz Operating Frequency

● Spread-Spectrum Options Available

● Short-Circuit, Thermal Protections

● Fixed 5.4ms Internal Soft-Start

The device offers fixed-output voltages of 5V and 3.3V,

as well as an adjustable version. The adjustable version

allows the user to program the output voltage between

1V and 10V by using a resistor-divider. Frequency is fixed

at 2.1MHz, which allows for small external components,

reduced output ripple, and minimized AM radio interfer-

ence. The device offers both forced-PWM and skip modes

of operation, with ultra-low quiescent current of 1.1µA

in skip mode. The device can be ordered with spread-

spectrum frequency modulation designed to minimize

EMI-radiated emissions due to the switching frequency.

● Fixed 5V/3.3V or Programmable Output-Voltage

Options (1V to 10V)

● 97% (Max) Duty-Cycle Operation with Low Dropout

● Current-Mode Control Architecture

The MAX16956 is available in a small (3mm x 3mm)

®

10-pin µMAX package and operates across the full auto-

motive temperature range of -40°C to +125°C. The device

is AEC-Q100 qualified.

Applications

● Automotive Body ECUs

● Point-of-Load Applications

● Distributed DC Power Systems

µMAX is a registered trademark of Maxim Integrated Products,

Inc.

19-6737; Rev 2; 3/14

MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Absolute Maximum Ratings

(Voltages Referenced to PGND)

SUP .......................................................................-0.3V to +42V

EN..............................................................-0.3V to V

BST to LX..............................................................................+6V

BST........................................................................-0.3V to +47V

Continuous Power Dissipation (T = +70°C)

A

(derate 12.9mW/ºC above +70°C) ............................1031mW

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).......................................+260ºC

+ 0.3V

SUP

MODE, OUT/FB, RESET................. ........-0.3V to V

+ 0.3V

BIAS

AGND...................................................................-0.3V to +0.3V

BIAS.................... .................................................-0.3V to +6.0V

OUT/FB Short-Circuit Duration..................................Continuous

(Note 1)

Package Thermal Characteristics

µMAX

Junction-to-Ambient Thermal Resistance (B )....... 77.6°C/W

Junction-to-Case Thermal Resistance (B ).................... 5°C/W

JC

JA

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer

board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.

Electrical Characteristics

(V

= V

= 14V, V

= 0V, T = T = -40

°

C to +125

°

C, unless otherwise noted. Typical values are at T = +25

°

C, unless

SUP

EN

MODE

A

J

A

otherwise noted.) (Note 2)

PARAMETER

Supply Voltage

SYMBOL

CONDITIONS

MIN

TYP

MAX

36

UNITS

V

3.5

V

SUP

Supply Voltage

T < 500ms (Note 3)

= 0V

42

SUP

V

0.75

1.1

1.8

32

3.0

5.0

70

EN

No load, ﬁxed 3.3V V

OUT

µA

No load, ﬁxed 5V V

OUT

Supply Current

UV Lockout

I

SUP

No load, adjustable V

OUT

V

= V

, no load, FPWM, no

MODE

BIAS

0.5

3.0

1

1.5

3.4

mA

V

switching

V

rising

3.2

0.4

5

BIAS

Hysteresis

BIAS Regulator Voltage

BIAS Current Limit

V

= 5.5V to 36V (MAX16956C/F only)

V

BIAS

SUP

10

mA

BUCK CONVERTER

6V ≤ V

≤

V

= 5V

4.9

3.2

5.0

3.3

5.2

3.4

SUP

OUT,5V

OUT

Voltage Accuracy

36V, I

= 0 to

V

LOAD

V

= 3.3V

300mA

OUT,3.3V

Output Voltage Range

FB Voltage Accuracy

FB Input Current

V

Adjustable output versions

Adjustable output versions, 6V ≤ V

1

10

V

OUT

V

≤ 36V

SUP

0.98

1.0

0.02

1

1.03

FB

I

V

= 1V

FB

µA

%

FB

FB Load Regulation

ΔV

I

= 0.3mA to 300mA

LOAD

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Electrical Characteristics (continued)

(V

= V

= 14V, V

= 0V, T = T = -40

°

C to +125

°

C, unless otherwise noted. Typical values are at T = +25

°

C, unless

SUP

EN

MODE

A

J

A

otherwise noted.) (Note 2)

PARAMETER

SYMBOL

CONDITIONS

≤ 36V

MIN

TYP

0.02

1000

500

MAX

UNITS

%/V

mΩ

FB Line Regulation

ΔV

6V ≤ V

SUP

LINE

High-Side DMOS R

R

V

= 5V, I = 200mA

2200

1200

DSON

ON,HS

BIAS

LX

Low-Side DMOS R

R

V

= 5V, I = 200mA

mΩ

DSON

ON,LS

LX

DMOS High-Side Current-Limit

Threshold

I

0.425

70

0.5

100

0.575

130

A

mA

A

MAX

DMOS High-Side Skip-Mode

Peak-Current Threshold

I

SKIP

DMOS Low-Side Zero-Crossing

Threshold

I

40

ZX

DMOS Low-Side Negative

Current-Limit Threshold

I

FPWM mode

(Note 3)

-0.320

NEG

Soft-Start Ramp Time

LX Rise Time

t

5.4

6

ms

ns

SS

t

RISE,LX

ON_MIN

Minimum On-Time

t

60

97

2.1

±6

ns

Maximum Duty Cycle

PWM Switching Frequency

Spread-Spectrum Range

RESET OUTPUT (RESET)

DC

%

MAX

f

1.95

2.25

MHz

%

SW

SS

Spread-spectrum option only

V

rising

falling

90

88

92

90

12

94

92

THR_RES

OUT

RESET Threshold

%V

OUT

V

THF_RES

OUT

RESET Debounce

t

µs

µA

V

DEB

RESET High Leakage Current

I

T = +25°C

A

1

LEAK,RES

RESET Low Level

V

Sinking 1mA

0.4

OUT,RES

LOGIC LEVELS

EN Input High Threshold

EN Input Low Threshold

EN Input Current

V

2.4

1.4

V

IH,EN

V

0.4

IL,EN

IN,EN

I

0.1

µA

V

MODE Input High Threshold

MODE Input Low Threshold

MODE Internal Pulldown

THERMAL PROTECTION

Thermal Shutdown

V

IH,MODE

V

IL,MODE

R

1000

kΩ

PD,MODE

T

(Note 3)

+175

+15

°C

SHDN

T

SHDN,HYS

Thermal-Shutdown Hysteresis

Note 2: Limits are 100% tested at T = +25°C (and/or T = +125°C). Limits over the operating temperature range and relevant

A

supply voltage range are guaranteed by design and characterization.

Note 3: Guaranteed by design; not production tested.

Note 4: When the typical minimum on-time of 80ns is violated, the device skips pulses.

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Typical Operating Characteristics

(

V

SUP

= V = 14V, T = +25°C, unless otherwise noted.)

EN A

3.3V EFFICIENCY vs. LOAD

CURRENT—SKIP MODE (1μA to 300μA)

5V EFFICIENCY vs. LOAD

CURRENT—SKIP MODE (1μA to 300μA)

3.3V EFFICIENCY vs. LOAD CURRENT

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

SKIP

90

80

70

60

50

40

30

20

10

0

PWM

0

0.0001

0.0002

0.0003

0

0.0001

0.0002

0.0003

0.000001

0.00001

0.0001

0.01

1

0.00005

0.00015

0.00025

0.00005

0.00015

0.00025

0.001

(A)

0.1

I

(A)

I

(A)

OUT1

3.3V FIXED-OUTPUT STARTUP

5V EFFICIENCY vs. LOAD CURRENT

WAVEFORM (PWM, 300mA LOAD)

MAX16956 toc05

100

V

SKIP

SUP

90

80

70

60

50

40

30

20

10

0

10V/div

V

PWM

OUT

2V/div

V

RESET

5V/div

V

LX

10V/div

0.000001

0.00001

0.0001

0.01

1

2ms/div

0.001

(A)

0.1

I

OUT1

NO-LOAD SUPPLY CURRENT

vs. TEMPERATURE (SKIP MODE)

5V FIXED-OUTPUT STARTUP

WAVEFORMS (SKIP, 300mA LOAD)

MAX16956 toc06

3.0

2.5

2.0

1.5

1.0

0.5

0

V

SUP

V

OUT

= 3.3V

10V/div

V

OUT

5V/div

V

RESET

5V/div

V

LX

10V/div

-40 -20

0

20 40 60 80 100 120 140

TEMPERATURE (°C)

2ms/div

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Typical Operating Characteristics (continued)

(

V

SUP

= V

= 14V, T = +25

°C, unless otherwise noted.

)

EN

A

LINE REGULATION (3.3V OUTPUT)

LOAD REGULATION (3.3V OUTPUT)

LOAD REGULATION (5V OUTPUT)

3

2

3

2

I

= 300mA

LOAD

2

1

PWM

SKIP

PWM

SKIP

1

0

-1

-2

-3

-1

-2

-3

-1

-2

-3

6

11

16

21

26

31

36

0

0.05 0.10 0.15 0.20 0.25 0.30

LOAD CURRENT (A)

0

0.05 0.10 0.15 0.20 0.25 0.30

LOAD CURRENT (A)

INPUT VOLTAGE (V)

LOAD-TRANSIENT RESPONSE

(3.3V, SKIP MODE)

LINE REGULATION (5V OUTPUT)

MAX16956 toc12

3

2

I

= 300mA

LOAD

I

LOAD

200mA/div

1

V

OUT

3.3V

100mV/div

AC-COUPLED

0

-1

-2

-3

V

PGOOD

5V/div

200µs/div

6

11

16

21

26

31

36

INPUT VOLTAGE (V)

LOAD-TRANSIENT RESPONSE

(3.3V, PWM MODE)

LOAD-TRANSIENT RESPONSE

(5V, SKIP MODE)

MAX16956 toc13

MAX16956 toc14

I

LOAD

200mA/div

V

OUT

100mV/div

AC-COUPLED

OUT

3.3V

5V

50mV/div

AC-COUPLED

V

PGOOD

5V/div

PGOOD

5V

5V/div

200µs/div

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Typical Operating Characteristics (continued)

(

V

SUP

= V = 14V, T = +25°C, unless otherwise noted.)

EN A

LOAD-TRANSIENT RESPONSE

(5V, PWM MODE)

3.3V FIXED-OUTPUT COLD-CRANK

RESPONSE (PWM, 300mA LOAD)

MAX16956 toc15

MAX16956 toc16

V

SUP

10V/div

I

LOAD

V

OUT

200mA/div

2V/div

V

OUT

5V

50mV/div

AC-COUPLED

V

BIAS

5V/div

V

PGOOD

5V/div

V

LX

10V/div

200µs/div

400ms/div

5V FIXED-OUTPUT COLD-CRANK

RESPONSE (SKIP, NO LOAD)

3.3V FIXED-OUTPUT DIPS AND DROPS

RESPONSE (PWM, 300mA LOAD)

MAX16956 toc17

MAX16956 toc18

V

SUP

10V/div

V

SUP

10V/div

V

OUT

5V/div

2V/div

V

BIAS

V

5V/div

BIAS

5V/div

V

LX

10V/div

400ms/div

40ms/div

5V FIXED DIPS AND DROPS

RESPONSE (SKIP, NO LOAD)

3.3V FIXED-OUTPUT SLOW V

SUP

RESPONSE (PWM, NO LOAD)

MAX16956 toc19

MAX16956 toc20

V

SUP

V

SUP

10V/div

V

OUT

5V/div

2V/div

V

BIAS

V

BIAS

5V/div

V

LX

10V/div

40ms/div

10s/div

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Typical Operating Characteristics (continued)

(

V

SUP

= V = 14V, T = +25°C, unless otherwise noted.)

EN A

SWITCHING FREQUENCY

vs. TEMPERATURE

5V FIXED-OUTPUT SLOW V

SUP

RESPONSE (SKIP, NO LOAD)

MAX16956 toc21

2.25

2.20

2.15

2.10

2.05

2.00

1.95

V

OUT

= 3.3V

V

SUP

10V/div

V

OUT

5V/div

V

BIAS

5V/div

V

LX

10V/div

-40 -20

0

20 40 60 80 100 120 140

TEMPERATURE (°C)

10s/div

SHUTDOWN CURRENT

vs. TEMPERATURE

SHORT-CIRCUIT RESPONSE

(PWM MODE)

MAX16956 toc23

2.0

1.6

1.2

0.8

0.4

0

I

LX

0A

500mA/div

V

LX

10V/div

3.3V

5V

V

OUT

2V/div

V

5V/div

PGOOD

-40 -20

0

20 40 60 80 100 120 140

TEMPERATURE (°C)

4ms/div

5V FIXED-OUTPUT LOAD-DUMP RESPONSE

(SKIP, V

= 13.5V TO 42V, NO LOAD)

SUP

MAX16956 toc25

V

SUP

10V/div

V

OUT

5V/div

V

BIAS

5V/div

100ms/div

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Pin Conﬁguration

TOP VIEW

+

EN

1

2

3

4

5

10

9

BST

SUP

OUT/FB

BIAS

MAX16956

LX

8

7

MODE

RESET

PGND

AGND

*

6

µMAX

*EXPOSED PAD

Pin Description

1

NAME

BST

FUNCTION

High-Side Driver Supply. Connect a 0.1µF bootstrap capacitor between LX and BST.

IC Supply Input. Connect a minimum of 4.7µF ceramic capacitor from SUP to PGND.

Buck Switching Node. LX is high impedance when the device is off.

2

SUP

3

LX

4

PGND

AGND

Power Ground. Connect to AGND under the device in a star conﬁguration.

Analog Ground. Connect to PGND under the device in a star conﬁguration.

5

6

RESET Open-Drain Reset Output. An external pullup resistor is required.

Mode Switch-Control Input. Connect to ground or leave open to enable skip-mode operation under light loads.

Connect to BIAS to enable forced-PWM mode. MODE has a 1MΩ internal pulldown.

7

8

MODE

BIAS

5V Internal Logic Supply. Connect a 1µF ceramic capacitor to AGND.

MAX16956A/B/D/E (Fixed Output): Buck Regulator Voltage-Sense Input. Bypass OUT to PGND with a

minimum 22µF X7R ceramic capacitor.

MAX16956C/F (Adjustable Output): Feedback Input. Connect FB to a resistive divider between the buck output

and AGND to set the output voltage.

9

OUT/FB

10

—

EN

EP

SUP Voltage-Compatible Enable Input. Drive EN low to disable the device. Drive EN high to enable the device.

Exposed Pad. Connect EP to a large copper ground plane for effective power dissipation. Do not use EP as the

only IC ground connection. EP must be connected to PGND.

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Block Diagram

MODE

REF

EN

HVLDO

BANDGAP

OSC

BST

SUP

BIAS

MAX16956

CLK

CURRENT SENSE

+

SLOPE COMP

SOFTSTART

OUT

FB

OUT

OR

FB

OUT/FB

LX

PWM

LOGIC

CONTROL

EAMP

BIAS

SW1

COMP

V

GOOD

SW2

PGND

RESET

AGND

NOTE 1: FOR INTERNAL FEEDBACK VERSION, SW1 IS OPEN AND SW2 CLOSED.

EXTERNAL PIN IS CALLED OUT.

NOTE 2: FOR EXTERNAL FEEDBACK VERSION, SW1 IS CLOSED AND SW2 OPEN.

EXTERNAL PIN IS CALLED FB.

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

providing current to the output. The output capacitor

stores charge when the inductor current exceeds the

required load current and discharges when the inductor

current is lower, smoothing the voltage across the load.

Detailed Description

The MAX16956 is a small, current-mode buck converter

that features synchronous rectification and requires no

external compensation network. The device operates

from a 3.5V to 36V supply voltage and can deliver up

to 300mA output current. Frequency is fixed at 2.1MHz,

which allows for small external components, reduced

output ripple, and guarantees no AM-band interference.

The device features load-line architecture to reduce the

output capacitance needed, potentially saving system

cost and size. The output voltage is positioned slightly

positive at no load, still within the tolerance window, to

take advantage of the fact that any load disturbance is

a load step only. This increases the amount of margin

available to the undershoot that occurs on a load step,

allowing a reduction in the required output capacitance.

As the load increases, a small but controlled amount

of load regulation (“load-line”) error occurs, so that at

heavier loads the voltage is positioned slightly below

nominal. This takes advantage of the fact that any load

disturbance is load released, increasing the amount of

margin available to the overshoot that occurs.

The device offers fixed output voltages of 5V and 3.3V.

The device also offers adjustable output-voltage versions

that can be set between 1V and 10V by using an exter-

nal resistive divider. Voltage quality can be monitored

by observing the RESET signal. The device offers both

forced-PWM and skip mode, with ultra-low-quiescent cur-

rent of 1.1µA in skip mode.

DC-DC Converter Control Architecture

The device step-down converter uses a PWM peak current-

mode control scheme, with a load-line architecture. Peak

current-mode control provides several advantages over

voltage-mode control, including precise control of the induc-

tor current on a cycle-by-cycle basis, simpler compensa-

tion, and inherent compensation for line voltage variation.

The device can operate in either forced-PWM or skip

mode. In forced-PWM mode, the converter maintains a

constant switching frequency, regardless of load, to allow

for easier filtering of the switching noise. The device

includes proprietary circuitry that dramatically reduces

quiescent current consumption in skip mode, improving

light-load efficiency. See the Forced PWM/Skip Modes

section for further details.

An internal transconductance amplifier establishes an

integrated error voltage. The heart of the PWM control-

ler is an open-loop comparator: one input is the inte-

grated voltage-feedback signal; the other consists of the

amplified current-sense signal plus slope-compensation

ramp. Integrated high-side current sensing is used, which

reduces component count and layout risk by eliminating

the need to carefully route sensitive external signals.

Error-amplifier compensation is also integrated, once

again simplifying the power-supply designer’s task while

eliminating external components.

System Enable (EN)

An enable control input (EN) activates the device from its

low-power shutdown mode. EN is compatible with inputs

from automotive battery level down to 3.5V. The high-

voltage compatibility allows EN to be connected to SUP,

KEY/KL30, or the inhibit pin (INH) of a CAN transceiver.

Linear Regulator Output (BIAS)

The device includes a 5V linear regulator output (BIAS)

that provides power to the internal circuit blocks. Connect

a 1µF ceramic capacitor from BIAS to AGND. Do not load

this pin externally.

At each rising edge of the internal clock, the high-side

MOSFET turns on until the PWM comparator trips, the

maximum duty cycle is reached, or the peak current limit

is reached (see the Current Limit/Short-Circuit Protection

section). During this on-time, current ramps up through

the inductor, storing energy in a magnetic field and

sourcing current to the output. The current-mode feed-

back system regulates the peak inductor current as a

function of the output-voltage error signal. During the

second-half of the cycle, the high-side MOSFET turns

off and the low-side MOSFET turns on. The inductor

releases the stored energy as the current ramps down,

Undervoltage Lockout

When V

drops below the undervoltage-lockout

BIAS

(UVLO) level of V

= 2.8V (typ), the device assumes

UVLO

that the supply voltage is too low for proper operation, so

the UVLO circuitry inhibits switching. When V rises

BIAS

above the UVLO rising threshold, the controller enters the

startup sequence and then resumes normal operation.

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

exceeds approximately 175°C, the device stops switching

until the die temperature drops by approximately 15°C

and then resumes operation, including going through

soft-start again.

Startup and Soft-Start

The device features an internal soft-start timer. The

output-voltage soft-start ramp time is 5.4ms (typ). If a

short circuit or undervoltage is encountered after the soft-

start timer has expired, the device is disabled for 13.4ms

(typ) and then reattempts soft-start again. This pattern

repeats until the short circuit has been removed.

Spread-Spectrum Option

The device has an internal spread-spectrum option to

optimize EMI performance. This is factory set on the D,

E, and F variants of the device. For spread-spectrum-

enabled variants of the device, the operating frequency is

varied ±6% centered on 2.1MHz. The modulation signal

is a triangular wave with a period of 230µs at 2.1MHz.

RESET Output

The device features an open-drain RESET output to

monitor the output voltage. The RESET output requires

an external pullup resistor. RESET goes high (high

impedance) after the regulator output increases above

92% of the nominal regulated voltage. RESET goes low

when the regulator output drops to below 90% of the

nominal regulated voltage.

Therefore, f

ramps down 6% and back to 2.1MHz in

SW

115µs and also ramps up 6% and back to 2.1MHz in

115µs. The cycle repeats.

Applications Information

Forced PWM/Skip Modes

Setting the Output Voltage

The device features a logic-level input (MODE) to switch

between forced-PWM and skip modes. Connecting MODE

to BIAS enables the forced-PWM operation. Connecting

MODE to ground, or leaving unconnected, enables skip-

mode operation with ultra-low-quiescent current of 1.1µA.

In skip-mode operation, the converter’s switching frequen-

cy is load dependent until the output load reaches the skip

threshold. At higher load current, the switching frequency

does not change and the operating mode is similar to the

forced-PWM mode. Skip mode helps improve efficiency

in light-load applications by allowing the converter to turn

on the high-side switch only when the output voltage falls

below a set threshold. As such, the converter does not

switch the MOSFETs on and off as often as is the case

in the forced-PWM mode. Consequently, the gate charge

and switching losses are much lower in skip mode.

The device’s adjustable output-voltage version (see the

Selector Guide for more details) allows the user to set

the output to any voltage between 1V and 10V. Connect

a resistive divider from output (V

) to FB to AGND to

OUT

set the output voltage (Figure 1). Select R2 (FB to AGND

resistor) less than or equal to 100kΩ. Calculate R1 (V

OUT

to FB resistor) with the following equation:





 V





OUT

R1= R2×

−1







V









FB 



where V = 1V (see the Electrical Characteristics).

FB

V

OUT

Current Limit/Short-Circuit Protection

The device has fault protection designed to protect itself

from abnormal conditions. If the output is soft shorted

(meaning the output is overloaded but over 50% of

regulation), cycle-by-cycle current limit limits how high

the inductor current goes for any cycle. If the output is

hard shorted to ground and the output falls to less than

50% of regulation, the part goes into a mode where it

switches until 15 cycles are ended by current limit, then

waits for 13.4ms before trying to soft-start again. This

mode of operation limits the amount of power dissipated

by the device under these conditions. The device also

has overtemperature protection. If the die temperature

R1

MAX16956

FB

R2

Figure 1. Adjustable Output-Voltage Setting

Maxim Integrated

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

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:

Inductor Selection

Three key inductor parameters must be specified for

operation with the device: inductance value (L), inductor

saturation current (I

), and DC resistance (R

). To

SAT

DCR

select inductance 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 determines the

inductor value as follows:

∆V

ESR

=

IN

∆I

2

L

I

+

OUT

where:

and:

(V

− V

)× V

OUT OUT

SUP

∆I =

L

V

× f

×L

SUP SW

V

×(V

× f

− V

)

OUT

SUP

×I

×LIR

SUP SW OUT

I

×D(1− D)

V

OUT

where V

, V

SUP OUT

, and I

are typical values (so that

OUT

C

=

and D =

IN

efficiency is optimum for typical conditions). The switching

frequency is 2.1MHz. Table 1 lists some of the inductor val-

ues for 300mA output current and several output voltages.

∆V × f

Q

SW

SUP

where I

is the maximum output current and D is the

OUT

duty cycle.

Input Capacitor

Output 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.

The output filter capacitor must have low enough ESR to

meet output ripple and load transient requirements. The

output capacitance must be high enough to absorb the

inductor energy while transitioning from full-load to no-

load conditions. When using high-capacitance, low-ESR

capacitors, the filter capacitor’s ESR dominates the out-

put voltage ripple. Therefore, the size of the output capac-

itor depends on the maximum ESR required to meet the

The input capacitor RMS current requirement (I

defined by the following equation:

) is

RMS

V

×(V

− V

)

OUT

SUP

I

= I

LOAD(MAX)

RMS

V

SUP

I

has a maximum value when the input voltage

RMS

output voltage ripple (V

) specifications:

RIPPLE(P-P)

equals twice the output voltage (V

= 2V

), so

SUP

OUT

I

= I

/2.

RMS(MAX)

LOAD(MAX)

V

= ESR×I

×LIR

LOAD(MAX)

RIPPLE(P−P)

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 actual capacitance value required relates to the

physical size needed to achieve low ESR, as well as to

the chemistry of the capacitor technology. Therefore, the

capacitor is usually selected by ESR and voltage rating

rather than by capacitance value.

The input voltage ripple is composed of ΔV (caused

Q

by the capacitor discharge) and ΔV

(caused by the

ESR

ESR of the capacitor). Use low-ESR ceramic capacitors

When using low-capacity filter capacitors, such as ceram-

ic capacitors, size is usually determined by the capacity

needed to prevent voltage droop and voltage rise from

causing problems during load transients. Generally, once

enough capacitance is added to meet the overshoot

requirement, undershoot at the rising-load edge is no

longer a problem.

with high ripple current capability at the input. Assume

Table 1. Inductor Values for 300mA Output

Current

V

/V

(V)

14V/5V

14V/3.3V

SUP OUT

10µH (typ) 10µH (typ)

22µH (max) 22µH (max)

INDUCTOR (µH) I

= 300mA

LOAD

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

efficient heat transfer. Connect the exposed pad to

PGND, ideally at the return terminal of the output

capacitor.

PCB Layout Guidelines

Careful PCB layout is critical to achieve low-switching

power losses and clean, stable operation. Use a multi-

layer board whenever possible for better noise immunity

and power dissipation. Follow these guidelines for good

PCB layout:

3) Isolate the power components and high-current path

from the sensitive analog circuitry. Doing so is essential

to prevent any noise coupling into the analog signals.

1) The input capacitor (4.7µF, see Figures 3 and 4) should

be placed immediately next to the SUP pin of the

device. Since the device operates at 2.1MHz switch-

ing frequency, this placement is critical for effective

decoupling of high-frequency noise from the SUP pin.

4) Keep the high-current paths short, especially at the

ground terminals. This practice is essential for stable,

jitter-free operation.

5) Connect PGND and AGND together at the return

terminal of the output capacitor. Do not connect them

anywhere else.

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 sides. Add a

few small vias or one large via on the copper pad for

6) Keep the power traces and load connections short.

This practice is essential for high efficiency.

7) Place the BIAS capacitor ground next to the AGND pin

and connect with a short and wide trace.

Maxim Integrated

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Typical Application Circuits

MAX16956

V

BAT

SUP

BST

LX

C

L

C

IN1

IN2

BST

4.7µF

0.1µF

10µH

0.1µF

NH

MODE

EN

V

OUT

3.3V/5V

OUT

BIAS

C

OUT

NL

22µF

C

L

1µF

RESET

AGND

PGND

Figure 2. MAX16956AUBA/V+ (5.0V Fixed) and MAX16956AUBB/V+ (3.3V Fixed), 10-Pin µMAX

MAX16956

V

BAT

SUP

BST

LX

C

L

C

IN1

IN2

BST

V

OUT

4.7µF

0.1µF

10µH

0.1µF

1V/10V

C

22µF

OUT

NL

R

TOP

MODE

EN

VARIES

FB

NL

R

50kΩ

BOT

BIAS

C

L

1µF

RESET

AGND

PGND

Figure 3. MAX16956AUBC/V+, Variable Output Voltage, 10-Pin µMAX

Maxim Integrated

│

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Ordering Information

PART

TEMP RANGE

-40°C to +125°C

PIN-PACKAGE

10 µMAX-EP*

MAX16956AUB_+

MAX16956AUB_/V+

Note: Insert the desired suffix letter (from the Selector Guide) into the blank to indicate the output voltage and spread-spectrum option.

/V denotes an automotive qualified part.

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

Selector Guide

PART

V

RESET TIME (µs)

SPREAD SPECTRUM

PIN-PACKAGE

10 µMAX-EP

OUT

MAX16956AUBA+

MAX16956AUBA/V+

MAX16956AUBB+

MAX16956AUBB/V+

MAX16956AUBC+

MAX16956AUBC/V+

MAX16956AUBD/V+

MAX16956AUBE/V+

MAX16956AUBF/V+

Fixed 5V

10

Off

On

Fixed 3.3V

Adjustable

Fixed 5V

Fixed 3.3V

Adjustable

Package Information

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 TYPE

PACKAGE CODE

OUTLINE NO.

21-0109

LAND PATTERN NO.

90-0148

10 µMAX

U10E+3

Maxim Integrated

│ 15

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MAX16956

36V, 300mA, Mini Buck Converter with

1.1µA I

Q

Revision History

REVISION REVISION

PAGES

CHANGED

DESCRIPTION

NUMBER

DATE

0

6/13

Initial release

—

8, 11, 15

15

Changed PGND to AGND for pin 8 in the Pin Description section, removed C1

from Figure 1, and added nonautomotive OPNs for MAX16956A, MAX16956B, and

MAX16956C versions

1

2

2/14

3/14

Removed future product references

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

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.

2014 Maxim Integrated Products, Inc.

│ 16


型号：	MAX16956AUBA+
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Switching Regulator, Current-mode, 0.575A, 2250kHz Switching Freq-Max, PDSO10, 3 X 3 MM, ROHS COMPLIANT, UMAX-10 开关光电二极管
文件：	总16页 (文件大小：1769K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

MAX16956AUBA+ [MAXIM]

相关型号：

MAX16956AUBA+T

MAX16956AUBA/V+

MAX16956AUBB+

MAX16956AUBB/V+

MAX16956AUBB/V+T

MAX16956AUBC+

MAX16956AUBD/V+

MAX16956AUBE/V+

MAX16956AUBF/V+

MAX16961RATEA/V+

MAX16961RAUEA/V+

MAX16961SATEA/V+