ADP1882-1.0-EVALZ Analog Devices Inc, ADP1882-1.0-EVALZ Datasheet - Page 21

• Manufacturer Part Number: ADP1882-1.0-EVALZ
• Description: 1 MHz Synchronous Current-Mode Buck Controller Eval. Board
• Manufacturer: Analog Devices Inc

Specifications of ADP1882-1.0-EVALZ

• Silicon Manufacturer: Analog Devices
• Application Sub Type: PWM Buck Controller
• Kit Application Type: Power Management - Voltage Regulator
• Silicon Core Number: ADP1882
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Although the ADP1882/ADP1883 have only four discrete current-
sense gain settings for a given R
outline several available options for the valley current setpoint
based on various R
Table 6. Valley Current Limit Program
R
(mΩ)
1.5
2
2.5
3
3.5
4.5
5
5.5
10
15
18
1
Refer to Figure 71 for more information and a graphical representation.
ON
Figure 71. Valley Current-Limit Value vs. R
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
47 kΩ
A
30.769
25.641
9
7
5
3
CS
1
= 3.4 V/V
A
RES = OPEN
2
CS
= 26.7V/V
3
for Each Programming Resistor (RES)
4
ON
5
values.
22 kΩ
A
23.08
15.38
12.82
6
CS
= 6.6 V/V
Valley Current Level
7
A
RES = 100kΩ
8
CS
ON
R
CURRENT
ON
= 13.4V/V
9 10 11 12 13 14 15 16 17 18
variable, Table 6 and Figure 71
ZERO
(mΩ)
CLIM
HS
Open
A
38.46
32.97
25.64
23.08
20.98
11.54
7.692
6.41
ON
CS
of the Lower-Side MOSFET
= 26.7 V/V
Figure 73. Idle Mode Entry Sequence Due to Current-Limit Violations
1
REPEATED CURRENT-LIMIT
VIOLATION DETECTED
A
RES = 22kΩ
CS
A
RES = 47kΩ
CS
= 3.4V/V
= 6.6V/V
100 kΩ
A
38.5
28.8
23.1
19.2
16.5
12.8
11.5
10.5
5.77
3.85
3.21
CS
= 13.4 V/V
Rev. 0 | Page 21
A PREDE
OF PULS
ALLO
TO
of 40
The valley current limit is programmed as outlined in Table 6
and Figure 71. The inductor chosen must be rated to handle the
peak current, which is equal to the valley current from Table 6
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).
HICCUP MODE DURING SHORT CIRCUIT
A current-limit violation occurs when the current across
the source and drain of the lower-side MOSFET exceeds the
current-limit setpoint. When 32 current-limit violations are
detected, the controller enters the idle mode and turns off the
MOSFETs for 6 ms, allowing the converter to cool down. Then,
the controller reestablishes soft start and begins to cause the
output to ramp up again (see Figure 73). While the output
ramps up, COMP is monitored to determine if the violation is
still present. If it is still present, the idle event occurs again,
followed by the full-chip power-down sequence. This cycle
continues until the violation no longer exists. If the violation
disappears, the converter is allowed to switch normally,
maintaining regulation.
TERMINED NUMBER
W THE CONVERTER
Figure 72. Valley Current-Limit Threshold in Relation to Inductor Ripple Current
COOL DOWN
INDUCTOR
ES IS COUNTED TO
CURRENT
0A
ΔI = 33%
OF 30A
VALLEY CURRENT-LIMIT
THRESHOLD (SET FOR 25A)
35A
30A
REINITIALIZED TO
MONITOR IF THE
SOFT START IS
STILL EXISTS
VIOLATION
MAXIMUM DC LOAD
OF 32.25A
ΔI = 45%
CURRENT
39.5A
32.25A
ADP1882/ADP1883
ΔI = 65%
OF 37A
49A
37A
OUTPUT
SWING
COMP
OUTPUT
COMP
2.4V
0.9V