Datasheet MP2161GJ Datasheet (MPS)

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MP2161

Synchronous Step Down Switcher

The Future of Analog IC Technology

2A, 6V, 1.5MHz, 17μA IQ, COT

In 8-pin TSOT23

DESCRIPTION

The MP2161 is a monolithic step-down switch mode converter with built-in internal power MOSFETs. It achieves 2A continuous output current from a 2.5V to 6V input voltage with excellent load and line regulation. The output voltage can be regulated as low as 0.6V.

The Constant-On-Time control scheme provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown.

The MP2161 is available in the small TSOT23-8 package and requires a minimum number of readily available standard external components.

The MP2161 is ideal for a wide range of applications including High Performance DSPs, FPGAs, PDAs, and portable instruments.

FEATURES

• Very Low I

• Default 1.5MHz Switching Frequency

• EN and Power Good for Power Sequencing

• Wide 2.5V to 6V Operating Input Range

Output Adjustable from 0.6V

• Up to 2A Output Current

• 100% Duty Cycle in Dropout

• 100m and 60m Internal Power MOSFET

Switches

• Cycle-by-Cycle Over Current Protection

• Short Circuit Protect with Hiccup Mode

• Stable with Low ESR Output Ceramic

Capacitors

• Available in a TSOT23-8 Package

: 17A

APPLICATIONS

• Wireless/Networking Cards

• Portable Instruments

• Battery Powered Devices

• Low Voltage I/O System Power

All MPS parts are lead-free and adhere to the RoHS directive. For MPS green status, please visit MPS website under Products, Quality Assurance page.

“MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc.

TYPICAL APPLICATION

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

ORDERING INFORMATION

Part Number* Package Top Marking

MP2161GJ TSOT23-8 AEB

* For Tape & Reel, add suffix –Z (e.g. MP2161GJ–Z);

PACKAGE REFERENCE

TOP VIEW

VIN

PGND

TSOT23-8

ABSOLUTE MAXIMUM RATINGS

(1)

Supply Voltage VIN...................................... 6.5V

......................................................................

-0.3V (-1.5V for <10ns) to 6.5V (7V for <10ns)

All Other Pins................................-0.3V to 6.5 V

Junction Temperature...............................150°C

Lead Temperature ....................................260°C

Continuous Power Dissipation (T

= +25°C)

(2)

……….….. ............................................... 1.25W

Storage Temperature............... -65°C to +150°C

Recommended Operating Conditions

(3)

Supply Voltage VIN.............................2.5V to 6V

Operating Junction Temp. (T

). -40°C to +125°C

AGND

OUT

Thermal Resistance

(4)

θJC

TSOT23-8.............................. 100 ..... 55... °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 ambient thermal resistance 

. The maximum allowable continuous power dissipation at

any ambient temperature is calculated by P (MAX)-TA)/JA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage.

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

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

(MAX), the junction-to-

, and the ambient temperature

(MAX) = (T

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

ELECTRICAL CHARACTERISTICS

(5)

VIN = 5V, TA = +25°C, unless otherwise noted.

Parameter Symbol Condition Min Typ Max Units

Feedback Voltage VFB

Feedback Current IFB V

PFET Switch On Resistance R

NFET Switch On Resistance R

DSON_P

DSON_N

Switch Leakage

PFET Current Limit 2.7 3.2 4.0 A

ON Time TON

Switching frequency Fs

Minimum Off Time T

Soft-Start Time T

MIN-OFF

SS-ON

Power Good Upper Trip Threshold PGH

Power Good Lower Trip Threshold PGL -10 %

Power Good Delay PGD 50 s

Power Good Sink Current Capability

Power Good Logic High Voltage V

Power Good Internal Pull Up Resistor

Under Voltage Lockout Threshold Rising

Under Voltage Lockout Threshold Hysteresis

PG-L

PG-H

2.15 2.3 2.45 V

260 mV

EN Input Logic Low Voltage 0.4 V

EN Input Logic High Voltage 1.2 V

EN Input Current

Supply Current (Shutdown) VEN=0V, VIN=3V 20 100 nA

Supply Current (Quiescent) VEN=2V, VFB=0.63V, VIN=5V 17 20 A

Thermal Shutdown

Thermal Hysteresis

Notes:

5) Guaranteed by design.

6) Guaranteed by characterization test.

(5)

150

(5)

2.5V  VIN  6V -3% 0.600 +3%

TA=-40oC to +85oC

= 0.6V 10 50 nA

(6)

-3.5% +3.5%

V/%

100 m

60 m

= 0V, V

= 0V and 6V

VIN=5V, V

=3.6V, V

=1.2V -20% 1500 +20% kHz/%

OUT

=-40oC to +85oC

= 6V

=1.2V 185

OUT

=1.2V 245

OUT

(6)

-25% 1500 +25% kHz/%

0 1 A

60 ns

1.5 ms

FB voltage respect to the regulation

+10 %

Sink 1mA 0.4 V

VIN=5V, VFB=0.6V 4.9 V

550 k

VEN=2V 1.5 A

=0V 0 A

°C °C

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

TYPICAL PERFORMANCE CHARACTERISTICS

VIN = 5V, V

= 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted.

OUT

Quiescent Current vs. Input Voltage

2 2.5 3 3 .5 4 4.5 5 5.5 6

INPUT VOLTAGE (V)

Shutdown Current vs. Input Voltage

0.003

0.0025

0.002

0.0015

0.001

0.0005

2 2.5 3 3.5 4 4.5 5 5.5 6

INPUT VOLTAGE (V)

Line Regulation Case Temp Rise

1.00

0.80

0.60

0.40

0.20

0.00

-0.20

-0.40

-0.60

-0.80

-1.00

Load=1A

Load=0A

23456

INPUT VOLTAGE (V)

Load=2A

VIN=3V, V

50 45

5 0

0 0.5 1 1.5 2 2.5

OUT

OUTPUT CURRE NT (A)

=1.2V

Load Regulation

2.00

1.50

1.00

0.50

0.00

-0.50

-1.00

-1.50

-2.00

VIN=5V

=6V

0 0.5 1 1.5 2 2.5

LOAD CURRENT (A)

Case Temp Rise

VIN=5V, V 50 45

5 0

0 0.5 1 1.5 2 2.5

=3.3V

OUT

OUTPUT CURRE NT (A)

Efficiency

100

VIN=3.3V

95 90

=5V

1 10 100 1000 10000

LOAD CURRENT(mA)

=6V

Efficiency

5/3.3VIN to 1.8V

100

VIN=5V VIN=3.3V

0 0.5 1 1.5 2 2.5

OUT

(A)

Efficiency

5VIN to 3.3V

100

0 0.5 1 1.5 2 2.5

OUT

(A)

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

VIN = 5V, V

= 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted.

OUT

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

VIN = 5V, V

= 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted

OUT

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

PIN FUNCTIONS

Pin # Name Description

Power Good Indicator. The output of this pin is an open drain with internal pull up resistor

1 PG

2 VIN

3 SW Switch Output

4 PGND Power ground

5 OUT Input sense pin for output voltage

6 AGND Analogy ground for internal control circuit

7 FB

8 EN On/Off Control

to IN. PGOOD is pulled up to IN when the FB voltage is within 10% of the regulation level, if FB voltage is out of that regulation range, it is LOW.

Supply Voltage. The MP2161 operates from a +2.5V to +6V unregulated input. C1 is needed to prevent large voltage spikes from appearing at the input.

Feedback pin. An external resistor divider from the output to GND, tapped to the FB pin, sets the output voltage.

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BLOCK DIAGRAM

VIN

Bias

Lo- Iq

Voltage

Refer ence

0.6 V

OUT

E.A.

Soft star t

Ramp

generator

MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

COMP

Lo-Iq

RST

PWM

Cons tant

On- Tim e

Pulse

FBCOMP

Lo-Iq

VOUT

Lo-Iq

PWM

Hi-Z

PDR V

Driver

NDRV

Main

Swit ch

(PCH)

Synchr onous

Rectifier (NCH)

FB for fix ed output

0. 66V

0. 54V

COMP

Figure 1: MP2161 Block Diagram

COMP

Lo-Iq

GND

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

OPERATION

MP2161 uses constant on-time control with input voltage feed forward to stabilize the switching frequency over full input range. At light load, MP2161 employs a proprietary control of low side switch and inductor current to eliminate ringing on switching node and improve efficiency.

Constant On-time Control

Compare to fixed frequency PWM control, constant on-time control offers the advantage of simpler control loop and faster transient response. By using input voltage feed forward, MP2161 maintains a nearly constant switching frequency across input and output voltage range. The ontime of the switching pulse can be estimated as:

T0.667s

OUT

=⋅μ

an internal 1Meg Ohm resistor from EN pin to ground.

Soft Start

MP2161 has built-in soft start that ramps up the output voltage in a controlled slew rate, avoiding overshoot at startup. The soft start time is about 1.5ms typical.

Power GOOD Indictor

MP2161 has an open drain with 550k pull-up resistor pin for power good indicator PGOOD. When FB pin is within +/-10% of regulation voltage, i.e. 0.6V, PGOOD pin is pulled up to IN by the internal resistor. If FB pin voltage is out of the +/-10% window, PGOOD pin is pulled down to ground by an internal MOS FET. The MOS FET has a maximum R

of less than

dson

100 Ohm.

To prevent inductor current run away during load transient, MP2161 fixes the minimum off time to be 60ns. However, this minimum off time limit will not affect operation of MP2161 in steady state in any way.

Light Load Operation

In light load condition, MP2161 uses a proprietary control scheme to save power and improve efficiency. The MP2161 will turn off the low side switch when inductor current starts to reverse. Then MP2161 works in discontinuous conduction mode (DCM) operation.

Enable

When input voltage is greater than the undervoltage lockout threshold (UVLO), typically 2.3V, MP2161 can be enabled by pulling EN pin to higher than 1.2V. Leaving EN pin float or pull down to ground will disable MP2161. There is

Current limit

MP2161 has a typical 3.2A current limit for the high side switch. When the high side switch hits current limit, MP2161 will touch the hiccup threshold until the current lower down. This will prevent inductor current from continuing to build up which will result in damage of the components.

Short Circuit and Recovery

MP2161 enters short circuit protection mode also when the current limit is hit, and tries to recover from short circuit with hiccup mode. In short circuit protection, MP2161 will disable output power stage, discharge soft-start cap and then automatically try to soft-start again. If the short circuit condition still holds after softstart ends, MP2161 repeats this operation cycle till short circuit disappears and output rises back to regulation level.

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

APPLICATION INFORMATION

COMPONENT SELECTION

Setting the Output Voltage

The external resistor divider is used to set the output voltage (see Typical Application on page

1). The feedback resistor R1 can not be too large neither too small considering the trade-off for stability and dynamic. Choose R1 to be around 120k to 200k. R2 is then given by:

0.6

The feedback circuit is shown as Figure 2.

MP2161

Figure 2: Feedback Network

Table 1 lists the recommended resistors value for common output voltages.

Table 1—Resistor Selection for Common

Output Voltages

(V) R1 (kΩ) R2 (kΩ)

OUT

1.0 200(1%) 300(1%)

1.2 200(1%) 200(1%)

1.8 200(1%) 100(1%)

2.5 200(1%) 63.2(1%)

3.3 200(1%) 44.2(1%)

Selecting the Inductor

A 0.68µH to 2.2µH inductor is recommended for most applications. For highest efficiency, the inductor DC resistance should be less than 15m. For most designs, the inductance value can be derived from the following equation.

V(VV)

×−

OUT IN OUT

VIf

×Δ ×

IN L OSC

Where I

is the inductor ripple current.

out

−

Vout

Choose inductor current to be approximately 30% of the maximum load current. The maximum inductor peak current is:

LOAD)MAX(L

Selecting the Input Capacitor

The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the AC current to the step-down converter while maintaining the DC input voltage. Use low ESR capacitors for the best performance. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 10µF capacitor is sufficient. For higher output voltage, 47uF may be needed for more stable system.

Since the input capacitor absorbs the input switching current it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by:

⎛

OUT

⎜

−×=

LOAD1C

⎜

⎝

The worse case condition occurs at VIN = 2V

OUT

⎞ ⎟

⎟

⎠

OUT

where:

LOAD

For simplification, choose the input capacitor whose RMS current rating greater than half of the maximum load current.

The input capacitor can be electrolytic, tantalum or ceramic. When using electrolytic or tantalum capacitors, a small and high quality ceramic capacitor, i.e. 0.1F, should be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple caused by capacitance can be estimated by:

IV V

Δ= × ×−

LOAD OUT OUT

fC1V V

SIN

⎛⎞ ⎜⎟

⎝⎠

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

Selecting the Output Capacitor

The output capacitor (C2) is required to maintain the DC output voltage. Ceramic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by:

Δ= ×− × +

V1R

Where L

OUT ESR

fL V 8fC2

S1 IN S

is the inductor value and R

⎛⎞

OUT OUT

⎜⎟

×××

⎝⎠

⎛⎞ ⎜⎟

⎝⎠

is the

ESR

equivalent series resistance (ESR) value of the output capacitor.

Using ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by:

V1

=×−

OUT

8f L C2

OUT OUT

×××

⎛⎞ ⎜⎟ ⎝⎠

In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to:

PCB Layout

Proper layout of the switching power supplies is very important, and sometimes critical for proper function. For the high-frequency switching converter, poor layout design can result in poor line or load regulation and stability issues.

The high current paths (GND, IN and SW) should be placed very close to the device with short, direct and wide traces. The input capacitor needs to be as close as possible to the IN and GND pins. The external feedback resistors should be placed next to the FB pin. Keep the switching node SW short and away from the feedback network.

AGND

V1R

=×−×

OUT ESR

fL V

⎛⎞

OUT OUT

⎜⎟

⎝⎠

The characteristics of the output capacitor also affect the stability of the regulation system.

VIN

GND

OUT

Figure 3: PCB Layout Recommendation

Design Example

Below is a design example following the application guidelines for the specifications:

Table 2: Design Example

fSW

OUT

1.2V

1500kHz

The detailed application schematic is shown in Figure 4. The typical performance and circuit waveforms have been shown in the Typical Performance Characteristics section. For more device applications, please refer to the related Evaluation Board Datasheets.

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

TYPICAL APPLICATION CIRCUITS

Figure 4: Typical Application Circuit

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

PACKAGE INFORMATION

See note 7 EXAMPLE TOP MA R K

PIN 1 ID

IAAAA

TSOT23-8

TOP V IEW

FRONT VIEW

DET AIL ' 'A' '

RECOMMENDED LAND PATTERN

SEATING PLANE

SEE DETAIL '' A''

SIDE VIEW

NOTE:

1) ALL DIMENSIONS ARE IN MILLIMETERS.

2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURR.

3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION.

4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX.

5) JEDEC REFERENCE IS MO-193, VARIATION BA.

6) DRAWING IS NOT TO SCALE.

7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)

NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.

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.

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