ADP1823 Datasheet, PDF (27/32 Pages) Analog Devices – Dual, Interleaved, Step-Down DC-to-DC Controller with Tracking

Table 4. Compensation Equations
Equations
f_CO
=
f_SW
10
f_LC
=
1
2 π LC
f_ESR
=
1
2 π R _ESR
C _OUT
A_FILTER
=
−40
dB
×
log
⎜⎛
⎜⎝
f_ESR
f_LC
⎟⎞
⎟⎠
−
20
dB
×
log
⎜⎛
⎜⎝
f_CO
f _ESR
⎟⎞
⎟⎠
A_MOD
=
20
log
⎜⎛
⎜⎝
V_IN
V_RAMP
⎟⎞
⎟⎠
ϕ_ESR
=
45°
× log ^{10 × fCO}
f_ESR
ϕ_B = 150° − ϕ_ESR
If ϕ_ESR ≥ 70° , use Type II compensation.
If ϕ_ESR < 70° , use Type III compensation.
Type II Compensation
K = tan⎜⎛ ^φB + 45°⎟⎞
⎝2
⎠
f_Z
=
f_CO
K
f_P = f_CO K
Select RTOP between 1 kΩ and 10 kΩ. A good starting value is 2 kΩ.
R_BOT
= ^{VFB RTOP}
V_OUT − V_FB
A_COMP = 0 dB − A_MOD − A_FILTER
⎜⎛ ^ACOMP ⎟⎞
R_Z = R_TOP × 10 ^{⎝ 20 âŽ} 
C_I
=
1
2π R_Zf_Z
C _HF
=
1
2 π R_Zf_P
Calculations
(70)
(71)
(72)
(73)
(74)
(75)
(76)
Calculations
(77)
(78)
(79)
(80)
(81)
(82)
(83)
(84)
ADP1823
Rev. A | Page 27 of 32