Datasheet

  
   
 
SLOS019E − SEPTEMBER 1988 − REVISED FEBRUARY 2005
21
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
†
Figure 31
−50 −25
50°
48°
46°
44°
42°
40°
T
A
− Free-Air Temperature − °C
−75 0 50
PHASE MARGIN
vs
FREE-AIR TEMPERATURE
100 12525 75
V
DD±
= ±5 V
R
L
= 10 kΩ
C
L
= 100 pF
om − Phase Margin
φ
m
Figure 32
0 200 400 600
PHASE MARGIN
vs
LOAD CAPACITANCE
800 1000
V
DD±
= ±5 V
R
L
= 10 kΩ
T
A
= 25°C
C
L
− Load Capacitance − pF
om − Phase Margin
φ
m
60°
50°
40°
30°
20°
10°
0°
†
Data at high and low temperatures are applicable only within the rated operating free-air temperature ranges of the various devices.
APPLICATION INFORMATION
capacitor selection and placement
The two important factors to consider when selecting external capacitors C
XA
and C
XB
are leakage and
dielectric absorption. Both factors can cause system degradation, negating the performance advantages
realized by using the TLC2652.
Degradation from capacitor leakage becomes more apparent with the increasing temperatures. Low-leakage
capacitors and standoffs are recommended for operation at T
A
= 125°C. In addition, guard bands are
recommended around the capacitor connections on both sides of the printed circuit board to alleviate problems
caused by surface leakage on circuit boards.
Capacitors with high dielectric absorption tend to take several seconds to settle upon application of power, which
directly affects input offset voltage. In applications where fast settling of input offset voltage is needed, it is
recommended that high-quality film capacitors, such as mylar, polystyrene, or polypropylene, be used. In other
applications, however, a ceramic or other low-grade capacitor can suffice.
Unlike many choppers available today, the TLC2652 is designed to function with values of C
XA
and C
XB
in the
range of 0.1 µF to 1 µF without degradation to input offset voltage or input noise voltage. These capacitors
should be located as close as possible to the C
XA
and C
XB
pins and returned to either V
DD−
or C RETURN. On
many choppers, connecting these capacitors to V
DD−
causes degradation in noise performance. This problem
is eliminated on the TLC2652.