ADP1878ACPZ-0.6-R7(RevA) View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
ADP1878ACPZ-0.6-R7
(Rev.:RevA)
(Rev.:RevA)
Analog Devices
ADP1878ACPZ-0.6-R7 Datasheet PDF : 40 Pages
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ADP1878/ADP1879
When the desired valley current limit (ICLIM) has been determined,
the current sense gain can be calculated as follows:
1.4 V
where:
RON is the channel impedance of the low-side MOSFET.
ACS is the current sense gain multiplier (see Table 6 and Table 7).
Although the ADP1878/ADP1879 have only four discrete current
sense gain settings for a given RON variable, Table 7 and Figure 71
outline several available options for the valley current setpoint
based on various RON values.
Table 7. Valley Current Limit Program (See Figure 71)
Valley Current Level (A)1
RON
47 kΩ,
(mΩ) ACS = 3 V/V
22 kΩ,
ACS = 6 V/V
Open,
100 kΩ,
ACS = 12 V/V ACS = 24 V/V
1.5
38.9
2
29.2
2.5
23.3
3
39.0
19.5
3.5
33.4
16.7
4.5
26.0
13
5
23.4
11.7
5.5
21.25
10.6
10
23.3
11.7
5.83
15 31.0
15.5
7.75
7.5
18 26.0
13.0
6.5
3.25
1 Blank cells are not applicable.
39
37
35
33
RES = 47kΩ
31
ACS = 3V/V
29
27
25
23
21
19
RES = 22kΩ
17
RES = NO RES
ACS = 6V/V
15
ACS = 12V/V
13
11
9 RES = 100kΩ
7 ACS = 24V/V
5
3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
RON (mΩ)
Figure 71. Valley Current-Limit Value vs. RON of the Low-Side MOSFET
for Each Programming Resistor (RES)
Data Sheet
The valley current limit is programmed as listed in Table 7 and
shown in Figure 71. The inductor that is chosen must be rated
to handle the peak current, which is equal to the valley current
from Table 7 plus the peak-to-peak inductor ripple current (see
the Inductor Selection section). In addition, the peak current
value must be used to compute the worst-case power dissipation
in the MOSFETs (see Figure 72).
49A
MAXIMUM DC LOAD
CURRENT
INDUCTOR
CURRENT
35A
39.5A
∆I = 65%
OF 37A
37A
CURRENT
SENSE
AMPLIFIER
OUTPUT
∆I = 33%
OF 30A
30A
∆I = 45%
OF 32.25A
32.25A
2.4V
VALLEY CURRENT-LIMIT
THRESHOLD (SET FOR 25A)
CS AMP
OUTPUT
SWING
0A
1V
Figure 72. Valley Current-Limit Threshold in Relation to Inductor Ripple Current
Rev. A | Page 20 of 40
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