MPM3680GRE_技术文档

MPM3680

18V 6A Step-Down Power Module

in 12x12x4mm QFN

The Future of Analog IC Technology

DESCRIPTION

FEATURES

The MPM3680 is an easy-to-use fully integrated

6A step-down DC/DC power module. It

integrates the DC/DC converter, power inductor,

input/output capacitors and the necessary



Complete 6A DC-to-DC Solution

Wide Input Voltage Range from 2.5V:

-- 2.5V to 18V with External 5V Bias

-- 4.5V to 18V with Internal Bias

1% Reference Voltage Over 0˚C to 70˚C

Junction Temperature Range

Adaptive COT Control for Ultrafast

Transient Response

Programmable Switching Frequency from

200KHz to 1MHz

Support Pre-Bias Start Up

Programmable Soft-Start Time with Default

3ms

Non-latch OCP, OVP and Thermal

Shutdown

resistors/capacitors in

a

compact QFN



12mmX12mmX4mm package. This total power

solution needs as few as two external

components (one resistor and one capacitor) to

work. MPM3680 can deliver 6A output current

over a wide input supply voltage range with

excellent load and line regulation.



The MPM3680 uses Constant-On-Time (COT)

control to provide fast transient response and

ease the loop stabilization.



The default under voltage lockout threshold is

internally set around 4.1V, but a resistor

network on the enable pin can increase this

threshold. The MPM3680 has an internal LDO

to power the control circuits and the integrated

power devices. This LDO can be disabled by an

external 5V to boost the efficiency.



Output Adjustable from 0.65V to 5V

QFN-57 (12mm x 12mm x 4mm) package

APPLICATIONS



Telecom and Networking Systems

Base Stations

Servers

Personal Video Recorders

Flat Panel Television and Monitors

Distributed Power Systems

The MPM3680 has an internal about 3ms soft

start (SS) timer. It can be increased with an

extra SS capacitor. An open drain power good

signal indicates that the output voltage is within

nominal voltage range.

All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive.

For MPS green status, please visit the MPS website under Quality

Assurance.

The MPM3680 has fully integrated protection

features that include over-current protection,

over-voltage protection and thermal shutdown.

“MPS” and “The Future of Analog IC Technology” are registered trademarks of

Monolithic Power Systems, Inc.

MPM3680 Rev. 1.02

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1

MPM3680 – 18V 6A STEP-DOWN POWER MODULE

TYPICAL APPLICATION

MPM3680 Rev. 1.02

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

ORDERING INFORMATION

Part Number*

Package

Top Marking

MPM3680GRE

QFN-57 (12mmx12mmx4mm)

See Below

TOP MARKING

MP3680: product code of MPM3680GRE;

MPS: MPS prefix;

YY: year code;

WW: week code:

LLL: lot number;

M: module;

PACKAGE REFERENCE

TOP VIEW

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

ABSOLUTE MAXIMUM RATINGS ⁽¹⁾

Recommended Operating Conditions ⁽³⁾

Supply Voltage V_IN........................... 4.5V to 18V

Output Voltage V_OUT........................ 0.65V to 5V

Enable Current I_EN……………………..…....1mA

Ambient Temperature................–40C to +85C

Junction Temperature..............–40C to +125C

Supply Voltage V_INto GND .............-0.3V to 21V

V

_SW(DC)to GND .......................... –1V to V_IN+0.3V

V_{SW5 (30ns)}to GND............. –3 V to V_IN+3V or 24V

_BST.......................................... –0.3 V to V_IN+6V

V

All Other Pins to AGND..................–0.3V to +6V

(2)

Continuous Power Dissipation (T_A=+25)

Thermal Resistance ⁽⁴⁾

θ_JA

θ_JC

QFN-65 (12mmx12mmx4mm)...................... 50W

Continuous Output Current........................... 8A

Junction Temperature...............................150C

Lead Temperature ....................................260C

Storage Temperature.............. –55C to +150C

QFN-57 (12mmx12mmx4mm)..16.2 ....6.3.. C/W

Notes:

1) Exceeding these ratings may damage the device.

2) The maximum allowable power dissipation is a function of the

maximum junction temperature T_J(MAX), the junction-to-

ambient thermal resistance θ_JA, and the ambient temperature

T_A. The maximum allowable continuous power dissipation at

any ambient temperature is calculated by P_D(MAX) = (T_J

(MAX)-T_A)/θ_JA. Exceeding the maximum allowable power

dissipation will cause excessive die temperature.

3) The device is not guaranteed to function outside of its

operating conditions.

(5)

MSL ................................................... Level 3

ESD (HBM)................................................. 2kV

ESD (CDM)............................................... 500V

4) Measured on JESD51-7, 4-layer PCB.

5) Need to get some test data from 1st sample for calibration

and evaluation for MSL Level 2.

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

ELECTRICAL CHARACTERISTICS

V_IN= 12V, V_OUT= 1.2V, R_trim=10kΩ, C_trim=560pF, T_J= 25C, unless otherwise noted.

Parameters

Symbol

Condition

Min

Typ

Max

Units

Input Voltage Range

5V External VCC

2.5

4.5

18

V

Input Voltage Range

V_IN

Output Voltage

Output Voltage Range ⁽⁶⁾

V_{OUT RANGE}

V_{OUT_DC_Load}

0.65

5

V

Output Voltage Accuracy

(Load Regulation) ⁽⁶⁾

C_OUT=5X47μF Ceramic,

I_OUT=0A to 6A

±0.5

±0.4

%Vout

Output Voltage Accuracy (Line

Regulation) ⁽⁶⁾

C_OUT=5X47μF Ceramic,

V_IN=4.5V to 18V, I_OUT=5A

V_{OUT_DC_Line}

%Vout

Quiescent Current

Current Limit

I_IN

V_EN=2V, V_FB=0.65V

700

12

860

15

1000

19

uA

A

Output Current Limit

Switching Frequency⁽⁶⁾

Switching Frequency

I_LIM

f_SW

I_OUT=5A

400

500

600

kHz

Over-voltage and Under-voltage Protection

V_{OVP_NON-}

OVP Non-latch Threshold ⁽⁷⁾

LATCH

With negative current limit

No negative current limit

117% 120% 123%

127% 130% 133%

V_FB

OVP Threshold ⁽⁶⁾

V_{OVP TH}

V_UVP

V_FB

UVP Threshold ⁽⁶⁾

47%

50%

53%

Reference And Soft Start

608

605

602

2

611

2.8

614

617

620

3.6

mV

ms

T_J= 0C to +70C

T_J= 0C to +120C

T_J= -40C to +125C

Reference Voltage ⁽⁸⁾

V_REF

t_SS

Soft Start Time

Timer ⁽⁶⁾

Minimum ON Time

Minimum OFF Time

T_{ON MIN}

20

30

40

ns

T_{OFF MIN}

200

360

420

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5

MPM3680 – 18V 6A STEP-DOWN POWER MODULE

ELECTRICAL CHARACTERISTICS

V_IN= 12V, V_OUT= 1.2V, R_trim=10kΩ, C_trim=560pF, T_J= 25C, unless otherwise noted.

Parameters

Symbol Condition

Min

Typ

Max

Units

Power Good

Power Good Rising Threshold ⁽⁷⁾

Power Good Falling Threshold ⁽⁷⁾

Power Good Low to High Delay ⁽⁷⁾

PG_Vth-Hi

PG_Vth-Lo

PG_Td

87%

91%

80%

2.5

94%

V_FB

ms

Power Good Sink Current

I_OL

I_{PG LEAK}V_PG=3.3V

V_IN=0V, Pull PGood up to

V_OL=600mV

12

mA

uA

Capability ⁽⁷⁾

Power Good Leakage Current ⁽⁷⁾

PG Low-Level Output Voltage

0.01

550

V_{OL_100}3.3V through a 100KΩ

500

600

700

mV

resistor.

V_IN=0V, Pull PGood up to

V_{OL_10}3.3V through a 10KΩ

resistor.

650

Enable ⁽⁷⁾

Enable Input Low Voltage

Enable Hysteresis

Enable Input Current

VIL_EN

1.1

1.3

250

0

1.5

V

V_EN-HYS

I_EN

mV

μA

V_EN= 2V

VCC Regulator ⁽⁷⁾

VCC Under Voltage Lockout

Threshold Rising

VCC_Vth

3.8

V

VCC Under Voltage Lockout

Threshold Hysteresis

VCC_HYS

V_CC

500

mV

VCC Regulator

4.8

0.5

V

VCC Load Regulation

Thermal Protection ⁽⁶⁾

Thermal Shutdown

I_CC=5mA

%

T_SD

150

°C

Thermal Shutdown Hysteresis

25

Notes:

6) Guaranteed by design

7) 100% tested for internal IC prior to module assembly

8) Guaranteed by production test and/or characterization for internal IC prior to module assembly

MPM3680 Rev. 1.02

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

PIN FUNCTIONS

Pin #

Name

Description

1, 2, 47, 50,

52

AGND

Analog/Signal Ground. It needs to be connected to GND on PCB layout.

Output Voltage DC Trimming. Connect this pin to pin DC_trim> first, and then to the

3

>DC_trim output voltage sense point through a resistor. The resistor value can be chosen

based on equation 1.

4, 6, 20, 26,

27, 37

N/C

Not connected. Keep these pins floating.

Output Voltage AC Trimming. Connect these pins to the output through a capacitor.

The capacitor value can be chosen based on equation 2.

5

AC_trim

7- 19, 53, 54

21-25, 55

SW

Switch Output. Keep them floating.

Module voltage output node.

VOUT

System Power Ground. Reference ground of the regulated output voltage. PCB

layout requires extra care. Connect using wide PCB traces.

28- 36, 56

GND

VIN

Supply Voltage. Supply power to the internal MOSFET and regulator. The MPM3680

operates from a +2.5V to +18V input rail with 5V external bias and from a +4.5V to

+18V input rail with internal bias. It requires input decoupling capacitors. Connect

using wide PCB traces and multiple vias.

38-41, 57

Frequency Set In. An internal 430K frequency set resistor is used if connecting this

pin to Pin FREQ<. Keep this pin floating if values other than 300K are needed.

42

43

>FREQ

EN

Enable. Digital input that turns the regulator on or off. Drive EN high to turn on the

regulator, drive it low to turn it off. Connect EN to IN through a pull-up resistor or a

resistive voltage divider for automatic startup. Do not float this pin.

Frequency Set Out. An internal 430K frequency set resistor is used if connecting this

44

FREQ> pin to Pin FREQ>. If values other than 430K are needed, connect the resistor

between this pin and pin VIN.

Output Voltage DC Trimming. Connect this pin to pin >DC_trim first, and then to the

DC_trim> output voltage sense point through a resistor. The resistor value can be chosen

based on equation 1.

45

46

48

Soft Start. Floating this pin has the default 3ms SS time. The SS time can be

extended by connecting an external capacitor between SS and AGND pins.

SS

Power Good. The output is an open drain signal. Require a pull-up resistor to a DC

PG

voltage to indicate high if the output voltage exceeds 91% of the nominal voltage.

There is a 2.5ms delay from FB ≥ 91% to PG goes high.

Internal 4.8V LDO Output. Power the driver and control circuits. Keep this pin floating.

Applying a 5V external bias can disable the internal LDO to boost the efficiency.

49

51

VCC

BST

Bootstrap. Keep this pin floating.

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7

MPM3680 – 18V 6A STEP-DOWN POWER MODULE

TYPICAL CHARACTERISTICS

V_IN=12V, V_OUT=1.2V, T_A=25˚C, unless otherwise noted.

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

TYPICAL CHARACTERISTICS (continued)

V_IN=12V, V_OUT=1.2V, T_A=25˚C, unless otherwise noted.

Load Transient Response

Power Up Through EN

0A

6A

V

EN

5V/div.

V

/AC

OUT

50mV/div.

V

OUT

500mV/div.

V

PG

5V/div.

I

OUT

2.5A/div.

5A/div.

10A/div.

Power Up Through Input

Output Ripple

0A

6A

0A

V

IN

V

IN

5V/div.

V

OUT

V

/AC

OUT

500mV/div.

20mV/div.

V

PG

V

PG

5V/div.

I

OUT

I

OUT

10A/div.

5A/div.

Output Ripple

Over Current Protection

Recovery

6A

OCP

V

PG

2V/div.

V

/AC

OUT

20mV/div.

V

OUT

500mV/div.

I

OUT

10A/div.

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

BLOCK DIAGRAM

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

OPERATION

Power Module Operation

At the beginning of each cycle, the high-side

MOSFET (HS-FET) turns ON when the feedback

voltage (V_FB) drops below the reference voltage

(V_REF), which indicates an insufficient output

voltage. The input voltage and the frequency-set

resistor determine the ON period as follows:

The MPM3680 is a high performance single

output synchronous switching mode DC-to-DC

power supply. It can deliver 6A continuous output

current. The MPM3680 can provide an output

voltage from 0.65V to 5V over a 4.5V to 18V (or

2.5V to 18V with 5V external VCC bias) wide

input voltage range.

6.1R_FREQ(k)

T_ON(ns) 

V (V)  0.4

IN

(1)

The MPM3680 is a complete power solution. It

integrates a constant-on-time (COT) control DC-

to-DC regulator, power devices, an inductor,

input/output capacitors and some other

supporting resistors and small capacitors. It only

needs as few as one external resistor and one

external small capacitor to operate.

After the ON period elapses, the HS-FET turns

off. It turns ON again when V_FBdrops below V_REF

.

By repeating this operation, the converter

regulates the output voltage to the desired level.

The integrated low-side MOSFET (LS-FET) turns

on when the HS-FET is OFF to minimize the

conduction loss. There is a dead short (or shoot-

through) between input and GND if both HS-FET

and LS-FET turn on at the same time. A dead-

time (DT) internally generated between HS-FET

OFF and LS-FETON, or LS-FET OFF and HS-

FET ON avoids shoot-through.

The MPM3680 is controlled by both the VCC

voltage and the EN signal. It can only be turned

on when both voltages are higher than the

thresholds.

The switching frequency is determined by a

frequency set resistor. The default switching

frequency with the integrated resistor is shown in

table 1. The default switching frequency

increases with the output voltage. The switching

frequency can also be programmed externally in

the range of 200KHz to 1000KHz. The details

can be found in the section of “SWITCHING

FREQUENCY SETTING” on Page 12.

Heavy-Load Operation

The MPM3680 utilizes constant-on-time control.

It has sufficient stability margin with simple loop

compensation. And it provides very good

transient response with a wide range of output

capacitors, even with all ceramic output

capacitors.

Figure 2—Heavy Load Operation

When the output current is high and the inductor

current is always above zero amps, it is called

continuous-conduction-mode (CCM). Figure 2

shows the CCM operation. When V_FBis below

The MPM3680 has a variable soft start timer to

smooth-out the output voltage during start-up.

The default (with SS pin floating) soft start timer

is about 3ms. The soft-start time can be

extended by adding a capacitor between SS pin

and AGND pin.

V

_REF, HS-FET turns on for a fixed interval

determined by the one-shot on-timer as per

equation 1. When the HS-FET turns off, the LS-

FET turns on until the next period.

PWM Operation

In CCM operation, the switching frequency is

fairly constant and is also called PWM mode.

The MPM3680 uses Constant-on-time (COT)

control to provide a fast transient response and

ease loop stabilization.

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

Light-Load Operation

The IC turns into PWM mode once the output

current exceeds the critical level. After that, the

switching frequency stays fairly constant over the

output current range.

As the load decreases, the inductor current

decreases too. When the inductor current

touches zero, the operation is transited from

continuous-conduction-mode

discontinuous-conduction-mode (DCM).

(CCM)

to

Switching Frequency

Selecting the switching frequency requires

trading off between efficiency and component

size. Low frequency operation increases

efficiency by reducing MOSFET switching losses,

but requires larger inductor and capacitor values

to minimize the output voltage ripple.

Figure 3 shows the light load operation. When

V_FBdrops below V_REF, HS-FET turns on for a

fixed interval determined by the one- shot on-

timer as per equation 1. When the HS-FET turns

off, the LS-FET turns on until the inductor current

reaches zero. In DCM operation, the V_FBdoes

not reach V_REFwhen the inductor current is

approaching zero. The LS-FET driver turns into

tri-state (high Z) whenever the inductor current

reaches zero. A current modulator takes over the

control of LS-FET and limits the inductor current

less than -1mA. Hence, the output capacitors

discharge slowly to GND through LS-FET. As a

result, this mode improves the efficiency greatly

at light load condition. At this condition, the HS-

FET does not turns ON as frequently as at heavy

load condition. This is called pulse skip mode.

The MPM3680 uses adaptive constant-on-time

(COT) control to generate a fairly constant

frequency at CCM condition, though the IC lacks

a dedicated oscillator. The ON time of HSFET

can be set by connecting a resistor between IN

pin and FREQ pin. It’s input voltage adaptive. So

for a fixed output voltage, the switching

frequency stays fairly constant. The switching

frequency can be set internally and externally.

Figure 4 shows that the switching frequency is

determined by the internal 430K resistor. The

430K resistor is connected to IN pin so that the

input voltage is feed-forwarded to the one-shot

ON-time timer. When operating in steady state at

CCM, the duty ratio stays at V_OUT/V_IN, so the

switching frequency is fairly constant over the

input voltage range. The switching frequency can

be determined by equation 3:

At light load or no load condition, the output

drops very slowly and the MPM3680 reduces the

switching frequency naturally and then achieves

high efficiency at light load.

Figure 3—Light Load Operation

As the output current increases from the light

load condition, the current modulator regulates

the operating period that becomes shorter. The

HS-FET turns ON more frequently. Hence, the

switching frequency increases correspondingly.

The output current reaches the critical level when

the current modulator time decreases to zero.

The critical output current level can be

determined as follows:

Figure 4

10⁶

(3)

F (kHz) 

SW

6.1 430(k) V (V)

IN



 T_DELAY(ns)

(V  V_OUT) V_OUT

V (V) 0.4 V_OUT(V)

IN

(2)

I_OUT



2LF_SW V

IN

Where T_DELAYis the comparator delay of about

5ns.

Where F_SWis the switching frequency.

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12

MPM3680 – 18V 6A STEP-DOWN POWER MODULE

resistor (R_DOWNfrom the EN pin to GND) to

determine the automatic start-up voltage:

Table 1 shows the switching frequency with

different common output voltages:

(R_UP R_DOWN

)

V

 1.5

(V)

(5)

Vo (V)

1

fs(KHz)

400

INSTART

R_DOWN

For example, for R_UP=100kΩ and R_DOWN=51kΩ,

the V_IN-STARTis set at 4.44V.

1.2

1.5

1.8

500

600

To reduce noise, add a 10nF ceramic capacitor

from EN to GND.

700

Table 1

An internal zener diode on the EN pin clamps the

EN pin voltage to prevent running away. The

maximum pull up current (assuming the worst

case 6V for the internal zener clamp) should be

limited to 1mA or less.

If a switching frequency other than those listed in

Table 1 is desired, an external frequency set

resistor can be connected as shown in figure 5:

Therefore, when driving EN with an external logic

signal, the driving voltage should be less than 6V.

When connecting EN to IN through a pull-up

resistor or a resistive voltage divider, select a

resistance that ensures a maximum pull-up

current of 1mA.

If using a resistive voltage divider and V_IN

exceeds 6V, then the minimum resistance for the

pull-up resistor R_UPshould meet:

Figure 5

V  6V

R_UP

6V

IN

(6)



 1m A

The switching frequency can be estimated

through equation (4) as follows:

R_DOWN

With only R_UP(the pull-down resistor, R_DOWN, is

not connected), then the VCC UVLO threshold

determines V_IN-START,so the minimum resistor

value is:

(4)

10⁶

F_SW(kHz) 

6.1R_FREQ(k)

V (V)  0.4

V (V)

IN



 T_DELAY(ns)

V_OUT(V)

IN

Where T_DELAYis the comparator delay of about

5ns.

V  6V

1m A

IN

(7)

R_UP



()

Typically, the MPM3680 is set to 200kHz to

1MHz applications. Thanks to its monolithic

structure, the MPM3680 is optimized to operate

at high switching frequencies at high efficiency.

High switching frequencies allow for physically

smaller LC filter components to reduce the PCB

footprint.

A typical pull-up resistor is 100kΩ.

VCC Power Supply

The MPM3680 has an internal VCC LDO to

supply the power to the internal circuits and

drives the power devices. This VCC LDO is

derived from the input supply. To ensure proper

operation, the minimum input voltage should be

4.5V.

An external 5V VCC bias can disable the internal

LDO. In this case, Vin can be as low as 2.5V.

The efficiency can be higher with external 5V

VCC bias. Figure 6 shows the comparison.

Configuring the EN Control

The power module turns on when EN goes high;

conversely it turns off when EN goes low. Do not

float the pin.

For automatic start-up, pull the EN pin up to input

voltage through a resistive voltage divider.

Choose the values of the pull-up resistor (R_UP

from the IN pin to the EN pin) and the pull-down

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

on the soft-start capacitor exceeds the sensed

output voltage at the FB pin.

Power Good (PG)

The MPM3680 has a power-good (PG) output.

The PG pin is the open drain of a MOSFET.

Connect it to VCC or some other voltage source

that measures less than 5.5V through a pull-up

resistor (typically 100kꢀ). After applying the input

voltage, the MOSFET turns on so that the PG pin

is pulled to GND before the SS is ready. After the

FB voltage reaches 91% of the REF voltage, the

PG pin is pulled high after a 2.5ms delay.

Figure 6

When the FB voltage drops to 80% of the REF

voltage or exceeds 120% of the nominal REF

voltage, the PG pin is pulled low.

Soft Start

The MPM3680 employs a soft start (SS)

mechanism to ensure a smooth output during

power-up. When the EN pin goes high, an

internal current source (20μA) charges the SS

capacitor. The SS capacitor voltage takes over

the REF voltage to the PWM comparator. The

output voltage smoothly ramps up with the SS

voltage. Once the SS voltage reaches the REF

voltage, it continues ramping up while V_REFtakes

over the PWM comparator. At this point, soft start

finishes and the device enters steady state

operation.

If the input supply fails to power the MPM3680,

the PG pin is also pulled low even though this pin

is tied to an external DC source through a pull-up

resistor.

Over-Current Protection (OCP)

The MPM3680 features two current limit levels

for over-current conditions: low-side valley

current limit and low-side negative current limit.

Low-Side Valley Current Limit: The device

monitors the inductor current during the LS-FET

ON state. If the LS-FET sourcing current is

higher than the internal positive-valley-current

limit, the HS-FET remains OFF and the LS-FET

remains ON for the next ON time. When the LS-

FET sourcing current drops below the valley

current limit, then the LS-FET turns off and the

HS-FET turns on again.

An internal 100nF SS capacitor is used. So the

default (with SS pin floating) SS time can be

estimated as:

100(nF) V_REF(V)

(8)

T_SS(ms) 

I_SS(uA)

So the default SS time is about 3ms.

If longer SS time is needed, an external SS

capacitor can be added between SS pin and

AGND pin. The external capacitor value can be

determined as follows:

The MPM3680 enters OCP non-latch protection

mode if the LS-FET sourcing valley current keeps

exceeding the valley current limit for a certain

period of time. During OCP, the device tries to

recover from the over-current fault with hiccup

mode: the chip disables the output power stage,

discharges the soft-start capacitor and then

automatically retries soft-start. The device

repeats this operation cycle as long as the over-

current condition still exists. When the over-

current condition disappears, the MPM3680

initiates a new SS to rise back to regulation level.

T_SS(ms)I_SS(uA)

(9)

C_SS(nF) 

100(nF)

V_REF(V)

Pre-Bias Startup

The MPM3680 has been designed for monotonic

startup into pre-biased loads. If the output is pre-

biased to a certain voltage during startup, the IC

will disable switching for both high-side and low-

side switches until the voltage

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MPM3680 – 18V 6A STEP-DOWN POWER MODULE

Low-Side Negative Current Limit: If the sensed

LS-FET negative current exceeds the negative

current limit, the LS-FET turns off immediately

and stays OFF for the remainder of the OFF

period. In this situation, both MOSFETs are OFF

until the end of a fixed interval. The HS-FET body

diode conducts the inductor current for the fixed

time.

IN

R_UP

EN Comparator

EN

R_DOWN

Over -Voltage Protection (OVP)

The MPM3680 monitors the output voltage using

the FB pin connected to the tap of a resistor

divider to detect over-voltage. It provides non-

latch OVP mode.

Figure 7—Adjustable UVLO Threshold

Thermal Shutdown

The MPM3680 has thermal shutdown. The IC

internally monitors the junction temperature. If

the junction temperature exceeds the threshold

value (minimum 150ºC), the converter shuts off.

This is a non-latch protection. There is about

25ºC hysteresis. Once the junction temperature

drops to about 125ºC, it initiates a soft startup.

If the FB voltage exceeds the nominal REF

voltage but remains lower than 120% of the REF

voltage (0.611V), both MOSFETs are off.

If the FB voltage exceeds 120% of the REF

voltage but remains below 130%, the LS-FET

turns on while the HS-FET remains off. The LS-

FET remains on until the FB voltage drops below

110% of the REF voltage or the low-side

negative current limit is hit.

If the FB voltage exceeds 130% of the REF

voltage, it enters a non-latch mode. The LS-FET

remains on until the FB voltage drops below

110% of the REF voltage, and the MPM3680

initiates a new SS to rise back to regulation level

and operates normally again.

UVLO protection

The MPM3680 has under-voltage lock-out

protection (UVLO). When the VCC voltage

exceeds the UVLO rising threshold, the

MPM3680 powers up. It shuts off when the VCC

voltage falls below the UVLO falling threshold

voltage. This is non-latch protection. The

MPM3680 is disabled when the VCC voltage falls

below 3.3 V. If an application requires a higher

UVLO threshold, use the two external resistors

connected to the EN pin as shown in Figure 9 to

adjust the startup input voltage. For best results,

use the enable resistors to set the input voltage

falling threshold (V_STOP) above 3.6 V. Set the

rising threshold (V_START) to provide enough

hysteresis to account for any input supply

variations.

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15

MPM3680 – 18V 6A STEP-DOWN POWER MODULE

APPLICATION INFORMATION

light load conditions. The Ctrim is still

recommended to boost the phase margin of the

system. A value between 100pF and 2.2nF is

recommended. The circuit connection can be

made as the following:

Setting the Output Voltage-Small ESR

Capacitors

When the output capacitors are all ceramic

capacitors or capacitors with small ESR, external

RAMP is injected through the R/C network

across the inductor. The circuit connection is as

follows:

MPM3680

L

VOUT

SW

R3

300K

402

Ctrim

Rtrim

R2

1K

Cout

402

AC_trim

DC_trim>

>DC_trim

FB

R1

10K

402

AGND

Figure 9

The Rtrim can be determined as follows to obtain

the desired output voltage:

Figure 8

V_OUT V_REF

Here is the procedure to find the values for Ctrim

and Rtrim:

(15)

R_TRIM(K) 

10

V_REF

a) Determine the Ton

Input Capacitor

5.3R_FREQ(K)

The input current to the step-down power module

is discontinuous, and therefore, it requires a

capacitor to supply the AC current to the step-

down power module while maintaining the DC

input voltage. Use ceramic capacitors for best

performance. During layout, Place the input

capacitors as close to the IN and GND pins as

possible.

(10)

T_ON(ns) 

V (V) 0.4

IN

b) Determine Ctrim. Choose a V_RAMParound

10mV-30mV for most of the applications.

V (V)  V_OUT(V)

R₃(K) V_RAMP(V)

IN

(11)

C_TRIM(pF) 

 T_ON(ns)

c) Find the average feedback voltage V_FB

The capacitance can vary significantly with

temperature. Use capacitors with X5R or X7R

ceramic dielectrics because they are fairly stable

over a wide temperature range.

V_RAMP(V)

(12)

V_{FB _ AVG}(V)  V_REF(V) 

2

d) Calculate Rtrim to get the desired output

voltage:

The capacitors must also have a ripple current

rating that exceeds the converter’s maximum

input ripple current. Estimate the input ripple

current as follows:

V_OUT(V)

(13)

R_o(K)  (

1)10(K)

V_{FB_ AVG}(V)

V_OUT

R_O(K)300(K)

300(K)R_O(K)

(16)

I_CIN I_OUT



(1

)

(14)

R_TRIM(K) 

V

IN

The worst-case condition occurs at V_IN= 2V_OUT

where:

,

Setting the Output Voltage-Large ESR

Capacitors

I_OUT

I_CIN



(17)

If one or more piece of the output capacitors

have large ESR, then there is no need of external

RAMP. Otherwise, it’ll generate group pulses at

2

MPM3680 Rev. 1.02

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16

MPM3680 – 18V 6A STEP-DOWN POWER MODULE

PCB Layout Recommendations

For simplification, choose an input capacitor with

an RMS current rating that exceeds half the

maximum load current.

1. Place the input/output capacitors on the same

side of the MPM3680, and as close to the

MPM3680 package as possible.

The input capacitance value determines the

converter input voltage ripple. Select a capacitor

value that meets any input voltage ripple

requirements.

2. A solid system ground layer is required to be

placed immediately below the surface layer with

the MPM3680.

Estimate the input voltage ripple as follows:

3. Thermal VIAs (18 mil diameter and 8 mil hole

size) are required to be placed underneath the

GND, IN and VOUT pads, as well as the edges

of the MPM3680 and the input/output capacitors.

I_OUT

V_OUT

(18)

V





(1

)

IN

F_SW C_IN

V

IN

The worst-case condition occurs at V_IN= 2V_OUT

where:

,

4. Keep the DC_trim traces as short as possible.

I_OUT

4 F_SW C_IN

1

(19)

V 



IN

Ctrim

Rtrim

AGND

SW

BST

AGND

SW

VCC

PG

SW

AGND

SS

N/C

VOUT

DCtrim>

FREQ>

EN

VOUT

N/C

>FERQ

VIN

CIN1

COUT1

COUT2

CIN2

CIN3

COUT3

Figure 10

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17

MPM3680 – 18V 6A STEP-DOWN POWER MODULE

Typical Design Parameter Table

The following table (Table 2) includes the recommended component values for typical designs.

Ref

1

2

3

4

5

6

7

8

Vin (V) Vout (V) Rtrim (KΩ)

Ctrim (pF)

560

220

330

560

270

680

560

330

560

470

330

680

330

270

330

270

390

180

150

Rfreq (KΩ)

NS

fs (KHz)

400

600

1000

300

500

Cout (uF) Ripple (mV)

12

1

6.49

10

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

3X47

5X47

7X47

5X47

3X47

5X47

7X47

5X47

3X47

11.6

16.4

5.0

7.6

3.8

NS

300

178

649

NS

2.2

1.2

1.5

1.8

2.5

3.3

5

24.0

38.4

11.2

14.8

3.2

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

33

34

35

36

39

40

41

42

NS

500

200

806

NS

1000

300

600

10

15

4.6

32.8

46.0

8.4

11.6

5.8

15

NS

600

15.8

21

34

243

750

NS

1000

400

750

7.0

25.4

49.6

7.6

9.4

8.8

NS

750

301

1000

698

432

909

549

1350

909

1000

400

600

12.4

34.2

46.4

18.8

25.2

9.8

13.0

31.6

21.2

6.0

10.2

49.2

36.0

20.8

28.8

34

35.7

34

600

1000

600

34

49.9

90.9

600

1000

600

1000

5

Table 2: Typical Design Examples

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18

MPM3680 – 18V 6A STEP-DOWN POWER MODULE

PACKAGE INFORMATION

QFN-57 (12mmx12mmx4mm)

NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third

party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not

assume any legal responsibility for any said applications.

MPM3680 Rev. 1.02

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19


型号：	MPM3680GRE
厂家：	MONOLITHIC POWER SYSTEMS
描述：	Switching Regulator, 19A, 1000kHz Switching Freq-Max, QFN-57 开关输出元件
文件：	总19页 (文件大小：1009K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

MPM3680GRE [MPS]

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