LT1029A_15 Datasheet, PDF (3/4 Pages) Linear Technology – 5V Bandgap Reference

LT1029/LT1029A
TYPICAL PERFOR A CE CHARACTERISTICS
Reverse Characteristics
1.0
0.9
0.8
0.7
0.6
0.5
0.4
T_J = 25°C
0.3
T_J = 125°C
0.2
0.1
T_J = – 55°C
0
01 2 34 56 7 8
OUTPUT TO GROUND VOLTAGE (V)
LT1029 • TPC01
APPLICATIO S I FOR ATIO
Output Trimming
Output voltage trimming on the LT1029 is nominally
accomplished with a potentiometer connected from
output to ground with the wiper tied to the trim pin. The
LT1029 was made compatible with existing references, so
the trim range is large; 5%, – 13%. This large trim range
makes precision trimming rather difficult. One solution is
to insert resistors in series with both ends of the
potentiometer. This has the disadvantage of potentially
poor tracking between the fixed resistors and the
potentiometer. A second method of reducing trim range is
to insert a resistor in series with the wiper of the
potentiometer. This works well only for a very small trim
range because of the mismatch in TCs between the series
resistor and the internal thin film resistors. These film
resistors can have a TC as high as 500ppm/°C. That same
TC is then transferred to the change in output voltage;
a 1% shift in output voltage causes a (500ppm) (1%) =
5ppm/°C change in output voltage drift. The worst case
error in initial output voltage for the LT1029A is 0.2% and
the LT1029 is 1%, so a series resistor is satisfactory if the
output is simply trimmed to nominal value. 1ppm/°C TC
shift would be the maximum expected for the LT1029A
and 5ppm/°C for the LT1029.
Shunt Capacitance
transient in operating current. A 1µF solid tantalum
capacitor is suggested for most situations where
bypassing is desirable.
Wide Trim Range (5%, – 13%)
V⁺
I ≥ 900µA
V_REF
25k
LT1029 • AI01
Narrow Trim Range
V⁺
I ≥ 800µA
V_REF = 5.000V
R1*
100k
TRIM RANGE
0.4% – LT1029A, R1 = 750k
LT1029 • TA02
1.2% – LT1029, R1 = 250k
Trimming Output to 5.120V
V⁺
I ≥ 800µA
V_REF = 5.120V
R1
41.2k
R2
5k
The LT1029 is stable with all values of shunt capacitance,
but values between 300pF and 0.01µF are not recom-
mended because they cause longer settling following a
R3
4.02k
LT1029 • AI03
1029afa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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