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LT3498

3498f

APPLICATIONS INFORMATION— OLED DRIVER

Inductor Selection

Several recommended inductors that work well with the

OLED driver of the LT3498 are listed in Table 5, although

there are many other manufacturers and devices that can

be used. Consult each manufacturer for more detailed

information and for their entire selection of related parts.

Many different sizes and shapes are available. Use the

equations and recommendations in the next few sections

to ﬁnd the correct inductance value for your design.

Table 5: Recommended Inductors

PART

(µH)

MAX

DCR

(Ω)

CURRENT

RATING

(mA)

VENDOR

LQH32CN100K53

LQH2MCN100K02

LQH32CN150K53

LQH2MCN150K02

0.3

1.2

0.58

1.6

450

225

300

200

Murata

www.murata.com

SD3110-100

SD3110-150

0.505

0.764

470

380

Cooper

www.cooperet.com

Inductor Selection—Boost Regulator

The formula below calculates the appropriate inductor

value to be used for the low noise boost regulator of

the LT3498 (or at least provides a good starting point).

This value provides a good tradeoff in inductor size and

system performance. Pick a standard inductor close to

this value. A larger value can be used to slightly increase

the available output current, but limit it to around twice

the value calculated below, as too large of an inductance

will decrease the output voltage ripple without providing

much additional output current. A smaller value can be

used (especially for systems with output voltages greater

than 12V) to give a smaller physical size. Inductance can

be calculated as:

OUT

IN MIN

=−

) • .

(

)

()

066

where VOUT2 is the desired output voltage and VIN(MIN) is

the minimum input voltage. Generally, a 10µH or 15µH

inductor is a good choice.

Capacitor Selection

The small size and low ESR of ceramic capacitors makes

them suitable for most OLED Driver applications. X5R and

X7R types are recommended because they retain their ca-

pacitance over wider voltage and temperature ranges than

other types such as Y5V or Z5U. A 4.7µF input capacitor

and a 10µF output capacitor are sufﬁcient for most appli-

cations for the OLED Driver. Always use a capacitor with

a sufﬁcient voltage rating. Many capacitors rated at 10µF,

particularly 0805 or 0603 case sizes, have greatly reduced

capacitance when bias voltages are applied. Be sure to check

actual capacitance at the desired output voltage. Generally

a 1206 size capacitor will be adequate. A 0.47µF capaci-

tor placed on the CAP node is recommended to ﬁlter the

inductor current while the larger 10µF placed on the VOUT

node will give excellent transient response and stability.

Table 6 shows a list of several capacitor manufacturers.

Consult the manufacturers for more detailed information

and for their entire selection of related parts.

Table 6. Recommended Ceramic Capacitor Manufacturers

MANUFACTURER

PHONE

URL

Taiyo Yuden

408-573-4150

www.t-yuden.com

AVX

843-448-9411

www.avxcorp.com

Murata

814-237-1431

www.murata.com

Kemet

408-986-0424

www.kemet.com

Setting Output Voltage and the Auxiliary

Reference Input

The OLED driver of the LT3498 is equipped with both an

internal 1.215V reference and an auxiliary reference input.

This allows the user to select between using the built-in

reference, and supplying an external reference voltage.

The voltage at the CTRL2 pin can be adjusted while the

chip is operating to alter the output voltage of the LT3498

for purposes such as display dimming or contrast adjust-

ment. To use the internal 1.215V reference, the CTRL2 pin

must be held higher than 1.5V. When the CTRL2 pin is

held between 0V and 1.5V the OLED driver will regulate

the output such that the FB2 pin voltage is nearly equal to

the CTRL2 pin voltage. At CTRL2 voltages close to 1.215V,

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