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EN5335QI

3A PowerSoC Voltage Mode Synchronous Buck PWM DC-DC Converter with Integrated Inductor 3-Pin Programmable Output

Altera Corporation 

EN5335QI

Theory of Operation

Table 1: Output Voltage Select Table:

Synchronous Buck Converter

The EN5335QI is a synchronous, pin

programmable power supply with integrated

power MOSFET switches and integrated

inductor. The nominal input voltage range is 2.4-

5.0V. The output can be set to common pre-set

voltages by connecting appropriate combinations

of 3 voltage selection pins to ground. The

feedback control loop is a type III voltage-mode

and the part uses a low-noise PWM topology. Up

to 3A of output current can be drawn from this

converter. The 5MHz operating frequency

enables the use of small-size output capacitors.

The power supply has the following protection

features:

 Over-current protection (to protect the IC

from excessive load current)

 Thermal shutdown with hysteresis

 Over-voltage protection

 Under-voltage lockout circuit to disable the

converter output when the input voltage is

less than approximately 2.2V

VS2*

0

0

0

0

1

1

1

1

VS1*

0

0

1

1

0

0

1

1

VS0* Output Voltage

0

3.3V

1

2.5V

0

1.8V

1

1.5V

0

1.25V

1

1.2V

0

0.8V

1

Reserved

Input Capacitor Selection

The EN5335QI requires about 20uF of input

capacitance. Low-cost, low-ESR ceramic

capacitors should be used as input capacitors for

this converter. The dielectric must be X5R or

X7R rated. In some applications, lower value

capacitors are needed in parallel with the larger,

capacitors in order to provide high frequency

decoupling. It is recommended to use 10V rated

MLCC capacitors.

Table 2. Recommended input capacitors.

Additional features include:

 Soft-start circuit, limiting the in-rush

current when the converter is powered up

 Power good circuit indicating whether the

output voltage is within 90% - 120% of the

programmed voltage

Output Voltage Programming

The EN5335QI output voltage is programmed

using a 3-pin voltage-ID or VID selector. Three

binary VID pins allow the user to choose one of

seven pre-set voltages. Refer to Table 1 for the

proper VID pin settings to choose VOUT.

Description

10uF, 10V, 10%

X7R, 1206

(2 capacitors needed)

22uF, 10V, 10%

X7R, 1210

(1 capacitor needed)

MFG

Murata

P/N

GRM31CR71A106KA01L

Taiyo Yuden LMK316B7106KL-T

Murata

GRM32ER71A226KE20L

Taiyo Yuden LMK325B7226KM-T

Output Capacitor Selection

The EN5335QI has been optimized for use with

approximately 50μF of output capacitance. Low

ESR ceramic capacitors are required with X5R or

X7R rated dielectric formulation. Y5V or

equivalent dielectric formulations must not be

used as these lose capacitance with frequency,

temperature and bias voltage.

The voltage select pins, VS0, VS1, and VS2, are

pulled-up internally and so will default to a logic

high, or “1”, if left “open”. Connecting the voltage

select pin to ground will result in a logic “0”.

Output ripple voltage is determined by the

aggregate output capacitor impedance. Output

impedance, denoted as Z, is comprised of

effective series resistance, ESR, and effective

series inductance, ESL:

00846

Z = ESR + ESL.

8

October 11, 2013

www.altera.com/enpirion

Rev J

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