8

LT1019

The worst-case error in initial output voltage for the

LT1019 is 0.2%, so a series resistor is satisfactory if the

output is simply trimmed to nominal value. The maximum

TC shift expected would be 1ppm/

°C.

Using the Temp Pin

The LT1019 has a TEMP pin like several other bandgap

references. The voltage on this pin is directly propor-

tional to absolute temperature (PTAT) with a slope of

approximately 2.1mV/

°C.Roomtemperaturevoltageis

therefore approximately (295

°K)(2.1mV/°C) = 620mV.

This voltage varies with process parameters and should

not be used to measure absolute temperature, but

rather relative temperature changes. Previous bandgap

references have been very sensitive to any loading on

the TEMP pin because it is an integral part of the

reference “core” itself. The LT1019 “taps” the core at a

special point which has much less effect on the refer-

ence. The relationship between TEMP pin loading and

a change in reference output voltage is less than

0.05%/

µA, about ten times improvement over previous

references.

Output Bypassing

The LT1019 is designed to be stable with a wide range of

load currents and output capacitors. The 4.5V, 5V, and

10V devices do not oscillate under any combination of

capacitance and load. The 2.5V device can oscillate when

sinking currents between 1mA and 6mA for load capaci-

tance between 400pF and 2

µF (see Figure 1).

If output bypassing is desired to reduce high frequency

output impedance, keep in mind that loop phase margin is

significantly reduced for output capacitors between 500pF

and 1

µF if the capacitor has low ESR (Effective Series

Resistance). This can make the output “ring” with tran-

Figure 1. Output Bypassing

sient loads. The best transient load response is obtained

by deliberately adding a resistor to increase ESR as shown

in Figure 1.

Use configuration (a) if DC voltage error cannot be com-

promised as load current changes. Use (b) if absolute

minimum peak perturbation at the load is needed. For best

transient response, the output can be loaded with

≥1mA

DC current.

APPLICATIO S I FOR ATIO

TYPICAL APPLICATIO S

Wide Range Trim

≥ ±5%

Narrow Trim Range (

±0.2%)

2

Ω TO 5Ω

LT1019

1019 F01

2

µF

TANTALUM

LT1019

2

µF TO 10µF

TANTALUM

2

Ω TO 5Ω

(a)

(b)

+

+

R1

25k

OUT

IN

LT1019

TRIM

GND

1019 TA03

R1

100k

OUT

IN

LT1019

TRIM

GND

1019 TA05

R2*

1.5M

*INCREASE TO 4.7M FOR LT1019A (

±0.05%)