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EP5388QI

800mA Synchronous Buck Regulator

With Integrated Inductor

3mm x 3mm x 1.1mm Package

July 2008

RoHS Compliant

Halogen Free

Product Overview

The EP5388QI is a synchronous buck

converter with integrated Inductor, PWM

controller, MOSFETS, and Compensation

providing the smallest possible solution size.

The EP5388QI requires only two small MLCC

capacitors to make a complete solution.

Integration of the inductor greatly simplifies

design, contains noise, reduces part count, and

reduces solution footprint. Low output ripple

ensures compatibility with RF systems.

The EP5388QI operates at a switching

frequency of 4 MHz, enabling this

unprecedented level of integration and small

external components. Type III voltage mode

control is used to provide high noise immunity

and wide control loop bandwidth.

The small footprint makes this part ideal for

space constrained portable applications.

Shutdown current of <1uA extends battery life

Output voltage level is programmed via a 3-pin

VID selector providing seven pre-programmed

output voltages along with an option for

external resistor divider.

Applications

• Noise Sensitive RF Applications

• Area Constrained Applications

• Wireless Data Applications

• Portable Gaming Devices

• Personal Media Players

• Advanced Mobile Processors, DSP, IO,

Memory, Video, Multimedia Engines

Ordering Information

Part Number Temp Rating (°C) Package

EP5388QI-T -40 to +85 16-pin QFN T&R

EP5388QI-E EP5388QI Evaluation Board

Product Highlights

Featuring Integrated Inductor Technology

• 3mm x 3mm x 1.1mm QFN package

• Only two low cost MLCC caps required

• 4 MHz switching frequency

• High efficiency, up to 94%

• Up to 800mA continuous output current

• Wide 2.4V to 5.5V input range

• VOUT range 0.6V to VIN – 0.5V

• 3-Pin VID output voltage programming

• 100% duty cycle capable

• Less than 1 µA standby current

• Low VOUT ripple for RF compatibility

• Short circuit and over current protection

• UVLO and thermal protection

• RoHS compliant; MSL 3 260°C reflow

Typical Application Circuit

VIN

VSense

Vin

VS1

VS2

VS0

EP5388QI 47uF

1206

4.7µF

0603

VOUT

Vout

GND

ENABLE

VFB

Voltage

Select

Figure 1. Typical application circuit.

July 2008 EP5388QI

Pin Description

Figure 2. EP5388QI Package Pin-out.

PIN NAME FUNCTION

1, 15, 16 NC(SW)

No Connect. These pins are internally connected to the common switch

node of the internal MOSFETs. NC(SW) pins are not to be electrically

connected to any external signal, ground, or voltage. However, they

must be soldered to the PCB. Failure to follow this guideline may result

in part malfunction or damage.

2,3 PGND Power Ground.

4 VFB

Feed back pin for external divider option. When using the external

divider option (VS2=VS1=VS0= high) connect this pin to the center of

the external divider. Set the divider such that VFB = 0.603V. The

“ground” side of the external divider should be connected to AGND.

5 VSENSE Sense pin for preset output voltages. Connect at the output capacitor.

6 AGND Analog ground. This is the quiet ground for the internal control circuitry

7,8 VOUT

Regulated Output Voltage. Refer to application section for proper layout

and decoupling.

9 NC

No Connect. This pin should not be electrically connected to any

external signal, voltage, or ground.. This pin must be soldered to the

PCB.

10, 11,

12 VS2,VS1,VS0

Output voltage select. VS2=pin10 VS1=pin11, VS0=pin12. Selects one

of seven preset output voltages or choose external divider by connecting

pins to logic high or low. (refer to section on output voltage select for

more detail).

13 ENABLE Output enable. Enable = logic high, disable = logic low.

14 VIN Input voltage pin.

July 2008 EP5388QI

Functional Block Diagram

Voltage

Select

DAC

Switch

VREF

(+)

(-)

Error

Amp

VSENSE

VFB

VOUT

VS0 VS1 VS2

Package Boundry

P-Drive

N-Drive

UVLO

Thermal Limit

Current Limit

Soft Start

Sawtooth

Generator

(+)

(-)

PWM

Comp

VIN

ENABLE

PGND

Logic

Compensation

Network

NC(SW)

AGND

Figure 3. EP5388QI Functional block diagram.

Absolute Maximum Ratings

CAUTION: Absolute Maximum ratings are stress ratings only. Functional operation beyond

recommended operating conditions is not implied. Stress beyond absolute maximum ratings may

cause permanent damage to the device. Exposure to absolute maximum rated conditions for

extended periods may affect device reliability.

PARAMETER SYMBOL MIN MAX UNITS

Input Supply Voltage VIN -0.3 7.0 V

Voltages on: ENABLE, VSENSE, VS0-VS2 -0.3 VIN + 0.3 V

Voltage on: VFB -0.3 2.7 V

Storage Temperature Range TSTG -65 150 °C

Reflow Temp, 10 Sec, MSL3 JEDEC J-STD-020C 260 °C

ESD Rating (based on Human Body Model) 2000 V

July 2008 EP5388QI

Recommended Operating Conditions

PARAMETER SYMBOL MIN MAX UNITS

Input Voltage Range VIN 2.4 5.5 V

Output Voltage Range VOUT 0.603 VIN – 0.5 V

Output Current IOUT 0 800 mA

Operating Ambient Temperature TA -40 +85 °C

Operating Junction Temperature TJ -40 +125 °C

Thermal Characteristics

PARAMETER SYMBOL TYP UNITS

Thermal Resistance: Junction to Ambient (0 LFM)* θJA 100 °C/W

Thermal Shutdown Trip Point TJ-TP +150 °C

Thermal Shutdown Trip Point Hysteresis 15 °C

* Based on a 2 oz. copper board and proper thermal design in line with JEDEC EIJ-JESD51 standards.

Electrical Characteristics

NOTE: VIN = 3.6V, CIN = 4.7µF 0603 MLCC, COUT = 47uF 1206 MLCC. TA = -40°C to +85°C unless otherwise noted.

Typical values are at TA = 25°C.

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS

Under-Voltage Lockout VUVLO V

IN going low to high 2.2 2.3 V

UVLO Hysteresis 0.145 V

VOUT Initial Accuracy ∆VOUT_Initl T

A = 25C, 2.4V ≤ VIN ≤ 5.5V -2 +2 %

Line Regulation ∆VOUT_linel 2.4V ≤ VIN ≤ 5.5V 0.06 %/V

Load Regulation ∆VOUT_load 0A ≤ ILOAD ≤ 800mA 0.0003

%/mA

Temperature Variation ∆VOUT_templ -40°C ≤ TA ≤ +85°C 0.008 %/°C

Overall VOUT Accuracy

(Line, Load, and

Temperature combined)

∆VOUT_All

2.4V ≤ VIN ≤ 5.5V

-40°C ≤ TA ≤ +85°C

0A ≤ ILOAD ≤ 800mA

-3 +3 %

Dynamic Voltage Slew

Rate† Vslew 1.125 1.5 1.875 V/mS

Continuous Output

Current IOUT -20°C ≤ TA ≤ +85°C

-40°C ≤ TA ≤ +85°C

800

750 mA

Shut-Down Current ISD Enable = Low 0.75 µA

PFET OCP Threshold ILIM 1000 mA

Feedback Pin Voltage VFB

2.4V ≤ VIN ≤ 5.5V

-20°C ≤ TA ≤ +85°C

0A ≤ ILOAD ≤ 800mA

0.585 0.603 0.621 V

Feedback Pin Input

Current IFB 10 nA

VS2-VS0 Threshold VSX_TH Pin = Low

Pin = High

0.0

1.4 0.4

VIN V

VS2-VS0 Pin Input

Current IVSX 1 nA

Enable Pin Voltage

Thresholds VEN_TH Pin = Low

Pin = High

0.0

1.4 0.2

VIN V

Enable Pin Input Current IEN ENABLE = Vin = 3.6V 2 µA

Operating Frequency FOSC 4 MHz

PFET On Resistance RDS(ON) 340 mΩ

NFET On Resistance RDS(ON) 270 mΩ

Dropout Resistance RDROPOUT 450 mΩ

July 2008 EP5388QI

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS

Soft-Start Operation

Soft-Start Slew Rate† V

ss 1.125 1.5 1.875 V/mS

Time to 90% Vout Tss Vout = 3.3V 2 mS

† Parameter guaranteed by design.

Typical Performance Characteristics

Typical performance characteristics are measured using the application circuit in Figure 1. All

measurements made at 25ºC.

0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80

Load Current (A)

Efficiency (%)

Efficiency, VIN = 3.3V, VOUT = 2.5V,1.8V,1.5V, 1.2V, Efficiency, VIN = 3.7V, VOUT = 2.5V,1.8V,1.5V, 1.2V,

top to bottom. top to bottom.

0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80

Load Current (A)

Efficiency (%)

Efficiency, VIN = 5V, VOUT = 3.3V, 2.5V,1.8V,1.5V, 1.2V, Output Ripple, VIN = 5V, VOUT = 1.2V; Load = 500mA.

top to bottom.

0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80

Load Curr ent (A)

Efficiency (%)

July 2008 EP5388QI

Output Ripple, VIN = 5V, VOUT = 3.3V; Load = 500mA. Output Ripple, VIN = 3.3V, VOUT = 1.2V; Load = 500mA.

Output Ripple, VIN = 3.3V, VOUT = 1.8V; Load = 500mA. Output Ripple, VIN = 3.3V, VOUT = 2.5V; Load = 500mA.

Transient, VIN = 5.0V, VOUT = 1.2V, Load = 0-800mA. Transient, VIN = 5.0V, VOUT = 3.3V, Load = 0-800mA.

July 2008 EP5388QI

Transient, VIN =3.3V, VOUT = 1.2V, Load = 0-800mA. Transient, VIN = 3.3V, VOUT = 1.8V, Load = 0-800mA.

Startup, VIN = 3.6V, VOUT = 1.5V, Load = 500mA. Shutdown, VIN = 3.6V, VOUT = 1.5V, Load = 500mA.

Enable in light blue; VOUT in Dark blue. Enable in light blue; VOUT in Dark blue.

Detailed Description

Functional Overview

The EP5388QI is a complete DCDC converter

solution requiring only two low cost MLCC

capacitors. MOSFET switches, PWM

controller, Gate-drive, compensation, and

inductor are integrated into the tiny 3mm x

3mm x 1.1mm package to provide the smallest

footprint possible while maintaining high

efficiency, low ripple, and high performance.

The converter uses voltage mode control to

provide the simplest implementation and high

noise immunity. The device operates at a

4MHz switching frequency. The high switching

frequency allows for a wide control loop

bandwidth providing excellent transient

performance. The high switching frequency

further enables the use of very small

components making possible this

unprecedented level of integration.

Enpirion’s proprietary power MOSFET

technology provides very low switching loss at

frequencies of 4 MHz and higher, allowing for

the use of very small internal components, and

high performance. Integration of the magnetics

virtually eliminates the design/layout issues

normally associated with switch-mode DCDC

converters. All of this enables much easier

and faster incorporation into various

applications to meet demanding requirements.

July 2008 EP5388QI

Output voltage is chosen from seven preset

values via a three pin VID voltage select

scheme. An external divider option enables

the selection of any voltage in 0.603V to

VIN-0.5V range. This reduces the number of

components that must be qualified and

reduces inventory burden. The VID pins can

be toggled on the fly to implement glitch free

dynamic voltage scaling between any two of

the seven preset VID voltage levels.

Protection features include under-voltage lock-

out (UVLO), over-current protection (OCP),

short circuit protection, and thermal overload

protection.

Integrated Inductor

Enpirion has introduced the world’s first

product family featuring integrated inductors.

The EP5388QI utilizes a proprietary low loss

integrated inductor. The use of an internal

inductor localizes the noises associated with

the output loop currents. The inherent shielding

and compact construction of the integrated

inductor reduces the radiated noise that

couples into the traces of the circuit board.

Further, the package layout is optimized to

reduce the electrical path length for the AC

ripple currents that are a major source of

radiated emissions from DCDC converters.

The integrated inductor significantly reduces

parasitic effects that can harm loop stability,

and makes layout very simple.

Stable Over Wide Range of Operating

Conditions

The EP5388QI utilizes an internal type III

compensation network and is designed to

provide a high degree of stability over a wide

range of operating conditions. The device

operates over the entire input and output

voltage range with no external modifications

required. The very high switching frequency

allows for a very wide control loop bandwidth.

Soft Start

Internal soft start circuits limit in-rush current

when the device starts up from a power down

condition or when the “ENABLE” pin is

asserted “high”. Digital control circuitry limits

the VOUT ramp rate to levels that are safe for

the Power MOSFETS and the integrated

inductor. The soft start ramp rate is nominally

1.5V/mS.

Over Current/Short Circuit Pr ote ction

When an over current condition occurs, VOUT is

pulled low. This condition is maintained for a

period of approximately 1.2 ms and then a

normal soft start cycle is initiated. If the over

current condition still persists, this cycle will

repeat.

Under Voltage Lockout

During initial power up an under voltage

lockout circuit will hold-off the switching

circuitry until the input voltage reaches a

sufficient level to insure proper operation. If

the voltage drops below the UVLO threshold

the lockout circuitry will again disable the

switching. Hysteresis is included to prevent

chattering between states.

Enable

The ENABLE pin provides a means to shut

down the converter or enable normal

operation. Transitioning from low to high will

cause the converter to go through a soft start

cycle. Transitioning from high to a low will

cause the device to discharge the output and

then shutdown. In shutdown mode, the device

quiescent current will be less than 1 uA.

NOTE: This pin must not be left floating.

July 2008 EP5388QI

Thermal Shutdown

When excessive power is dissipated in the

chip, the junction temperature rises. Once the

junction temperature exceeds the thermal

shutdown temperature the thermal shutdown

circuit turns off the converter thus allowing the

device to cool. When the junction temperature

decreases by 15°C, the device will go through

the normal startup process.

Application Information

Output Voltage Select

To provide the highest degree of flexibility in

choosing output voltage, the EP5388QI uses a

3 pin VID, or Voltage ID, output voltage select

arrangement. This allows the designer to

choose one of seven preset voltages, or to use

an external voltage divider. Internally, the

output of the VID multiplexer sets the value for

the voltage reference DAC, which in turn is

connected to the non-inverting input of the

error amplifier. This allows the use of a single

feedback divider with constant loop gain and

optimum compensation, independent of the

output voltage selected.

Table 1 shows the various VS2-VS0 pin logic

states and the associated output voltage

levels. A logic “1” indicates a connection to VIN

or to a “high” logic voltage level. A logic “0”

indicates a connection to ground or to a “low”

logic voltage level. These pins can be either

hardwired to VIN or GND or alternatively can be

driven by standard logic levels. Logic low is

defined as VSX ≤ 0.4V. Logic high is defined as

1.4V ≤ VSX ≤ VIN. Any level between these two

values is indeterminate. These pins must not

be left floating.

External Voltage Divider

As described above, the external voltage

divider option is chosen by connecting the

VS0, VS1, and VS2 pins to VIN or logic high.

The EP5388QI uses a separate feedback pin,

VFB, when using the external divider. VSENSE

must be connected to VOUT as indicated in

Figure 4.

VIN

VSense

Vin

VS1

VS2

VS0

EP5388QI 47µF

1206

4.7uF

0603

VOUT

Vout

GND

ENABLE

VFB

Figure 4. External Divider application circuit.

The output voltage is nominally selected by the

following formula:

(

)

10.603V

OUT

Then Rb is given as:

Ω

−

=603.0

603.0

OUT

Ra must be chosen as nominally 200KΩ to

maintain loop gain. VOUT can be programmed

over the range of 0.603V to VIN-0.5V.

Dynamically Adjustable Output

The EP5388QI is designed to allow for

dynamic switching between the seven

predefined VID voltage levels. The inter-

VS2 VS1 VS0 VOUT

0 0 0 3.3V

0 0 1 2.5V

0 1 0 1.8V

0 1 1 1.5V

1 0 0 1.25V

1 0 1 1.2V

1 1 0 0.8V

1 1 1 User

Selectable

Table 2. VID voltage select settings.

July 2008 EP5388QI

voltage slew rate is optimized to prevent

excess undershoot or overshoot as the output

voltage levels transition. The slew rate is

identical to the soft-start slew rate of 1.5V/mS.

Dynamic transitioning between internal VID

settings and the external divider is not allowed.

Input and Output Capacitors

The input capacitance requirement is 4.7uF

0603 MLCC. Enpirion recommends that a low

ESR MLCC capacitor be used.

A variety of output capacitor configurations are

possible depending on footprint and ripple

requirements. For typical applications, it is

recommended to use a single 47uF 1206

MLCC capacitor. Ripple performance can be

improved by using 2 x 22uF 0805 MLCC

capacitors.

A single 10uF 0805 MLCC can be used if VOUT

programming is accomplished using an

external resistor divider, with the addition of a

10pF phase lead capacitor as shown in Figure

5. Note that in this configuration, VSENSE

should NOT be connected to VOUT. Ra and Rb

values are calculated as shown in the external

voltage divider section.

The Input and the output capacitor must use a

X5R or X7R or equivalent dielectric

formulation. Y5V or equivalent dielectric

formulations lose capacitance with frequency,

bias voltage, and temperature and are not

suitable for switch-mode DC-DC converter

output filter applications.

Contact Enpirion Applications for information

on other output capacitor usage.

VIN

VSense

Vin

VS1

VS2

VS0

EP5388QI

10µF

0805

4.7uF

0603

VOUT

Vout

GND

ENABLE

VFB

10pF

Figure 5. Applications circuit for COUT = 1 x 10uF 0805.

Layout Considerations*

*Optimized PCB layout file is downloadable from the Enpirion website to assure first pass design success.

Refer to figure 6 for the following layout recommendations.

Recommendation 1: The input and output filter capacitors should be placed as close to the

EP5388QI as possible to reduce EMI from input and output loop AC currents. This reduces the

physical area of these AC current loops.

Recommendation 2: The system ground plane should be the first layer immediately below the

surface layer (PCB layer 2). If it is not possible to make PCB layer 2 the system ground plane, a local

ground island should be created on PCB layer 2 under the Enpirion device and including the area

under the input and output filter capacitors. This ground plane, or ground island, should be

continuous and uninterrupted underneath the Enpirion device and the input and output filter

capacitors.

Recommendation 3: The surface layer ground pour should include a “slit” as shown in figure 6 to

separate the input and output AC loop currents. This will help reduce noise coupling from the input

current loop to the output current loop.

July 2008 EP5388QI

Recommendation 4: Multiple small vias (approximately 0.25mm finished diameter) should be used

to connect the ground terminals of the input and output capacitors, and the surface ground pour

under the device, to the system ground plane. If a local ground island is used on PCB layer 2, the

vias should connect to the ground island and continue down to the PCB system ground plane.

Recommendation 5: The AGND pin should be connected to the system ground plane using a via as

described in recommendation 4. AGND must NOT be connected to the surface layer ground pour.

Recommendation 6: As with any switch-mode DC-DC converter, do not run any sensitive signal or

control lines under the converter package.

Vias Slit

Figure 6. PCB layout recommendation.

Recommended PCB Footprint

July 2008 EP5388QI

Package Dimensions

July 2008 EP5388QI

Contact Information

Enpirion, Inc.

685 US Route 202/206 Suite 305

Bridgewater, NJ 08807

Phone: +1 908-575-7550

Fax: +1 908-575-0775

Enpirion reserves the right to make changes in circuit design and/or specifications at any time without notice. Information furnished by Enpirion is

believed to be accurate and reliable. Enpirion assumes no responsibility for its use or for infringement of patents or other third party rights, which may

result from its use. Enpirion products are not authorized for use in nuclear control systems, as critical components in life support systems or equipment

used in hazardous environment without the express written authority from Enpirion.