lt1029amh Linear Technology Corporation, lt1029amh Datasheet - Page 3

• Manufacturer Part Number: lt1029amh
• Description: 5v Bandgap Reference
• Manufacturer: Linear Technology Corporation

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
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
TYPICAL PERFOR A CE CHARACTERISTICS
U
U
W
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.
U
W
0.6
1.0
0.9
0.8
0.7
0.5
0.4
0.3
0.2
0.1
0
0
Reverse Characteristics
T
J
U
= 125°C
1
OUTPUT TO GROUND VOLTAGE (V)
2
T
J
= – 55°C
3
4
transient in operating current. A 1µF solid tantalum
capacitor is suggested for most situations where
bypassing is desirable.
5
T
J
= 25°C
6
LT1029 • TPC01
7
V
+
8
I ≥ 800µA
Wide Trim Range (5%, – 13%)
R1*
V
Trimming Output to 5.120V
+
LT1029 • TA02
V
I ≥ 800µA
+
Narrow Trim Range
I ≥ 900µA
100k
V
LT1029/LT1029A
REF
R1
41.2k
R2
5k
R3
4.02k
TRIM RANGE
0.4% – LT1029A, R1 = 750k
1.2% – LT1029, R1 = 250k
= 5.000V
25k
V
LT1029 • AI01
REF
V
= 5.120V
LT1029 • AI03
REF
1029afa
3