ST1CC40 Datasheet, PDF (13/37 Pages) STMicroelectronics – 3 A monolithic step-down current source with synchronous rectification

ST1CC40
Application notes
Equation 2
_Z = -_E----_S---_R------_-¹--_C-----_O----_U----_T-
Equation 3
_P = _R-----_L---_O----_A---_D---¹--_---_C-----_O----_U----_T- + ^m-----_L-^C----_-^--_C-^--¹-_O----–_U----_T^D----_-^--_f--–_S----_W⁰---^,--⁵--
where:
Equation 4
 ^mC

=
1 + ^SS-----^en-


S_e
=
V_pp  f_SW



S_n
=
-^V----^I-^N-----–---_L--^V----^O----^U----^T-  R_i
S_n represents the slope of the sensed inductor current, S_e the slope of the external ramp
(V_PP peak-to-peak amplitude) that implements the slope compensation to avoid sub-
harmonic oscillations at duty cycle over 50%.
The sampling effect contribution F_H(s) is:
Equation 5
F_Hs = -₁----+------_---------_{n--------s--}¹_{----Q----------P-----+-------s------2--n2--}
where:
Equation 6
_n =   f_SW
and
Equation 7
Q_P = _-----_---_---_m-----_C-----_---_--₁--¹---–-----_D----_----–----₀----_,-₅----_-
6.3
Error amplifier compensation network
The ST1CC40 device embeds the error amplifier (see Figure 6) and a pre-defined
compensation network which is effective in stabilizing the system in most of the application
conditions.
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