Datasheet

LTC2970/LTC2970-1
33
29701fc
APPLICATIO S I FOR ATIO
WUU
U
4. Solve for R30B and R31B.
RB
RAVVmV
V
RR
FB
FB
30
40 236 0 8 10
1
10
1
0
0
≤
•−−−
()
•+
μ .
220
10 5 236 0 8 0 8 10
08
⎛
⎝
⎜
⎞
⎠
⎟
=
• −−−(. . . )
.
k AVVmV
V
Ωμ
••+
⎛
⎝
⎜
⎞
⎠
⎟
=
1
4 750
1
5 970
2 870
,,
,
ΩΩ
Ω
RB
RAVVmV
V
RR
FB
FB
31
41 236 0 8 10
1
11
1
1
1
≤
•−−−
()
•+
μ .
221
10 5 236 0 8 0 8 10
08
⎛
⎝
⎜
⎞
⎠
⎟
=
• −−−(. . . )
.
k AVVmV
V
Ωμ
••+
⎛
⎝
⎜
⎞
⎠
⎟
=
1
3 880
1
8 250
2 863
,,
,
ΩΩ
Ω
For coincident tracking to occur Equation 17 also must
be satisfi ed:
RB
R
RB
R
30
20
31
21
=
→=•= • =RB
RB
R
R30
31
21
20
2 863
8 250
5 970 2 078
,
,
,,
Ω
Ω
ΩΩΩ
→= •= • =RB
RB
R
R31
30
20
21
2 870
5 970
8 250 3 957
,
,
,,
Ω
Ω
ΩΩΩ
Let R30B = 2,100Ω and R31B = 2,890Ω.
5. Solve for R30A and R31A.
Referring to Equation 18:
RA
R
R
R
VV
V
DC MAX DC NOM
DC
30
20
1
20
10
00
≤
+
⎛
⎝
⎜
⎞
⎠
⎟
•
−
,,
00
30
5 970
1
5 970
4 750
,
,
,
,
NOM
RB
⎛
⎝
⎜
⎞
⎠
⎟
−=
+
⎛
⎝
⎜
⎞
⎠
Ω
Ω
Ω
⎟⎟
•
−
⎛
⎝
⎜
⎞
⎠
⎟
−=
105 1
1
2 100 50 806
.
,,ΩΩ
RA
R
R
R
VV
V
DC MAX DC NOM
DC
31
21
1
21
11
11
≤
+
⎛
⎝
⎜
⎞
⎠
⎟
•
−
,,
11
31
8 250
1
8 250
3 880
,
,
,
,
NOM
RB
⎛
⎝
⎜
⎞
⎠
⎟
−=
+
⎛
⎝
⎜
⎞
⎠
Ω
Ω
Ω
⎟⎟
•
−
⎛
⎝
⎜
⎞
⎠
⎟
−=
105 1
1
2 890 49 888
.
,,ΩΩ
Let R30A = 49.9kΩ and R31A = 48.7kΩ.
6. Solve for Channel 1’s tracking counter delay relative to
Channel 0, CH1_A_DELAY_TRACK().
First, recalculate the values of V
DCn,NOM
based on the fi nal
values of R1n and R2n:
VV
R
R
IR
V
DC NOM FB FB0
1
20
10
20
08 1
,
.
′
=•+
⎛
⎝
⎜
⎞
⎠
⎟
+• =
• ++
⎛
⎝
⎜
⎞
⎠
⎟
+=
5 970
4 750
0 1 805
,
,
.
Ω
Ω
V
VV
DC NOM1
08 1
8 250
3 880
0 2 501
,
.
,
,
.
′
=•+
⎛
⎝
⎜
⎞
⎠
⎟
+=
Ω
Ω
VV
Next, apply Equation 19:
CH A DELAY TRACK
VV
R
DC NOM DC NOM
1
10
__ _ ()
,,
=
′
−
′
()
•
331
21
141
2 501 1 805
2 890
B
R
A count R
VV
μ /
..
,
•
=
−
()
•
Ω
88 250
1105
23
,
/.
Ω
ΩμA count k
counts
•
=
7. Solve for the IDAC0 and IDAC1 terminal tracking codes,
Chn_a_idac_track[7:0].
Ch a idac Ch a idac
V
A
070170
255
08
1
__ [:] __ [:]
.
==
−
μ
//.LSB k•
=
10 5
179
Ω