Datasheet LT1019 (Analog Devices) - 8

LT1019
U U W U APPLICATIO S I FOR ATIO
The worst-case error in initial output voltage for the capacitance and load. The 2.5V device can oscillate when LT1019 is 0.2%, so a series resistor is satisfactory if the sinking currents between 1mA and 6mA for load capaci- output is simply trimmed to nominal value. The maximum tance between 400pF and 2µF (see Figure 1). TC shift expected would be 1ppm/°C. If output bypassing is desired to reduce high frequency
Using the Temp Pin
output impedance, keep in mind that loop phase margin is significantly reduced for output capacitors between 500pF The LT1019 has a TEMP pin like several other bandgap and 1µF if the capacitor has low ESR (Effective Series references. The voltage on this pin is directly propor- Resistance). This can make the output “ring” with tran- tional to absolute temperature (PTAT) with a slope of approximately 2.1mV/°C. Room temperature voltage is VIN VIN therefore approximately (295°K)(2.1mV/°C) = 620mV. This voltage varies with process parameters and should 2Ω TO 5Ω not be used to measure absolute temperature, but LT1019 LT1019 rather relative temperature changes. Previous bandgap 2Ω TO 5Ω + 2µF TO 10µF references have been very sensitive to any loading on + 2µF TANTALUM the TEMP pin because it is an integral part of the TANTALUM reference “core” itself. The LT1019 “taps” the core at a 1019 F01 (a) (b) special point which has much less effect on the refer-
Figure 1. Output Bypassing
ence. The relationship between TEMP pin loading and a change in reference output voltage is less than sient loads. The best transient load response is obtained 0.05%/µA, about ten times improvement over previous by deliberately adding a resistor to increase ESR as shown references. in Figure 1.
Output Bypassing
Use configuration (a) if DC voltage error cannot be com- promised as load current changes. Use (b) if absolute The LT1019 is designed to be stable with a wide range of minimum peak perturbation at the load is needed. For best load currents and output capacitors. The 4.5V, 5V, and transient response, the output can be loaded with ≥ 1mA 10V devices do not oscillate under any combination of DC current.
U TYPICAL APPLICATIO S Wide Range Trim
≥ ±
5% Narrow Trim Range (
±
0.2%)
OUT VOUT OUT VOUT V IN IN V IN IN R2* LT1019 LT1019 R1 1.5M R1 TRIM 25k TRIM 100k GND GND 1019 TA03 *INCREASE TO 4.7M FOR LT1019A (±0.05%) 1019 TA05 1019fd 8