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LT3012HFEPBF

250mA, 4V to 80V Low Dropout Micropower Linear Regulator

Linear Technology 

LT3012

APPLICATIONS INFORMATION

IN OUT

LT3012

VIN

ADJ

GND

VOUT

R2

+

R1

3012 F01

VOUT = 1.24V

1 + R2

R1

+ (IADJ)(R2)

VADJ = 1.24V

IADJ = 30nA AT 25°C

OUTPUT RANGE = 1.24V TO 60V

Figure 1. Adjustable Operation

The adjustable device is tested and specified with the

ADJ pin tied to the OUT pin and a 5μA DC load (unless

otherwise specified) for an output voltage of 1.24V. Speci-

fications for output voltages greater than 1.24V will be

proportional to the ratio of the desired output voltage to

1.24V; (VOUT/1.24V). For example, load regulation for an

output current change of 1mA to 250mA is –7mV typical at

VOUT = 1.24V. At VOUT = 12V, load regulation is:

(12V/1.24V) • (–7mV) = –68mV

Output Capacitance and Transient Response

The LT3012 is designed to be stable with a wide range of

output capacitors. The ESR of the output capacitor affects

stability, most notably with small capacitors. A minimum

output capacitor of 3.3μF with an ESR of 3Ω or less is

recommended to prevent oscillations. The LT3012 is a

micropower device and output transient response will be

a function of output capacitance. Larger values of output

capacitance decrease the peak deviations and provide

improved transient response for larger load current

changes. Bypass capacitors, used to decouple individual

components powered by the LT3012, will increase the

effective output capacitor value.

Extra consideration must be given to the use of ceramic

capacitors. Ceramic capacitors are manufactured with a

variety of dielectrics, each with different behavior across

temperature and applied voltage. The most common

dielectrics used are specified with EIA temperature char-

acteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and

Y5V dielectrics are good for providing high capacitances

in a small package, but they tend to have strong voltage

and temperature coefficients as shown in Figures 2 and 3.

When used with a 5V regulator, a 16V 10μF Y5V capacitor

can exhibit an effective value as low as 1μF to 2μF for the

DC bias voltage applied and over the operating tempera-

ture range. The X5R and X7R dielectrics result in more

stable characteristics and are more suitable for use as the

output capacitor. The X7R type has better stability across

temperature, while the X5R is less expensive and is avail-

able in higher values. Care still must be exercised when

using X5R and X7R capacitors; the X5R and X7R codes

only specify operating temperature range and maximum

capacitance change over temperature. Capacitance change

due to DC bias with X5R and X7R capacitors is better than

Y5V and Z5U capacitors, but can still be significant enough

to drop capacitor values below appropriate levels. Capaci-

tor DC bias characteristics tend to improve as component

case size increases, but expected capacitance at operating

voltage should be verified.

20

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10μF

0

X5R

–20

–40

–60

Y5V

–80

–100

0 2 4 6 8 10 12 14 16

DC BIAS VOLTAGE (V)

3012 F02

Figure 2. Ceramic Capacitor DC Bias Characteristics

40

20

0

X5R

–20

–40

Y5V

–60

–80

BOTH CAPACITORS ARE 16V,

–100 1210 CASE SIZE, 10μF

–50 –25 0 25 50 75

TEMPERATURE (°C)

100 125

3012 F03

Figure 3. Ceramic Capacitor Temperature Characteristics

3012fd

9

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