FAN53168MTC FAIRCHILD [Fairchild Semiconductor], FAN53168MTC Datasheet - Page 23

• Manufacturer Part Number: FAN53168MTC
• Description: 6-Bit VID Controlled 2-4 Phase DC-DC Controller
• Manufacturer: FAIRCHILD [Fairchild Semiconductor]

PRODUCT SPECIFICATION
I
To reduce the input-current di/dt to below the recommended
maximum of 0.1A/µs, an additional small inductor (L > 1µH
@ 15A) should be inserted between the converter and the
supply bus. That inductor also acts as a filter between the
converter and the primary power source.
TUNING PROCEDURE FOR THE FAN53168
1. Build circuit based on compensation values computed
2. Hook up dc load to circuit, turn on and verify opera-
DC Loadline Setting
3. Measure output voltage at no-load (V
Figure 7. Efficiency vs. Output Current (Circuit of Figure 1)
REV. 1.0.0 6/9/03
I
R
CRMS
CRMS
CS2 NEW
from design spreadsheet.
tion.Also check for jitter at no-load and full-load.
within tolerance.
100
(
80
60
40
20
=
=
0
0
D I
0.125 65A
)
×
=
O
R
×
×
10
CS2 OLD
------------- 1
n D
(
×
1
OUTPUT CURRENT – A
×
20
)
–
----------------------- - 1
3 0.125
×
×
(
---------------------------------------------
(
V
1
V
NL
NL
30
µ
–
–
V
–
V
FLCOLD
FLHOT
40
=
NL
10.5A
)
)
). Verify it is
50
60
4.
5.
6.
7.
8.
9.
10. Measure output ripple at no-load and full-load with
AC Loadline Setting
11. Remove dc load from circuit and hook up dynamic load.
12.
13. Set dynamic load for a transient step of about 40A at
14. Measure output waveform (may have to use dc offset on
15. You will see a waveform that looks something like
R
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ -
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -
R
Measure output voltage at full-load cold (V
Let board soak for ~10 minutes at full-load and measure
output (V
couple of millivolts, adjust R
Equations 35 and 37.
Repeat Step 4 until cold and hot voltage measurements
remain the same.
Measure output voltage from no-load to full-load using
5A steps. Compute the loadline slope for each change
and then average to get overall loadline slope (R
If R
the following to adjust the R
Repeat Steps 6 and 7 to check loadline and repeat
adjustments if necessary.
Once complete with dc loadline adjustment, do not
change R
scope and make sure it is within spec.
CS NEW
CS1 OLD
1kHz with 50% duty cycle.
scope to see waveform). Try to use vertical scale of 100
mV/div or finer.
Figure 8. Use the horizontal cursors to measure V
and V
UNDERSHOOT OR OVERSHOOT THAT HAPPENS
IMMEDIATELY AFTER THE STEP.
R
(
PH NEW
(
OMEAS
(
)
)
=
×
DCDRP
R
TH 25°C
PH
FLHOT
)
(
=
is off from R
, R
)
as shown. DO NOT MEASURE THE
R
+
CS1
(
PH OLD
R
). If there is a change of more than a
CS2 OLD
R
CS OLD
(
, R
(
(
CS2
)
)
µ
–
)
+
R
×
R
O
, or R
CS2 NEW
TH 25°C
R
----------------------
by more than 0.05 mW, use
(
(
1
OMEAS
PH
R
CS1
)
TH
)
O
)
×
values:
(
and R
R
for rest of procedure.
CS1 OLD
(
CS2
)
–
R
TH 25°C
using
FLCOLD
(
FAN53168
)
OMEAS
)
–
ACDRP
------------------------
R
TH 25°C
).
(37)
(
1
23
).
)