ISL6237 Datasheet, PDF (20/35 Pages) Intersil Corporation – High-Efficiency, Quad-Output, Main Power Supply Controllers for Notebook Computers

ISL6237
.
TABLE 2. APPROXIMATE K-FACTOR ERRORS
SMPS
SWITCHING
APPROXIMATE
FREQUENCY K-FACTOR K-FACTOR
(kHz)
(µs)
ERROR (%)
(t_ON = GND, REF,
400
2.5
±10
or OPEN), VOUT1
(t_ON = GND),
VOUT2
500
2.0
±10
(t_ON = VCC),
VOUT1
200
5.0
±10
(t_ON = VCC, REF,
300
3.3
±10
or OPEN), VOUT2
For loads above the critical conduction point, the actual
switching frequency is:
f
=
-----^V----^O-----^U----^T-----+-----^V----^D----^R----^O-----^P----¹------
t_ON(V_IN + V_DROP2)
(EQ. 2)
where:
• V_DROP1 is the sum of the parasitic voltage drops in the
inductor discharge path, including synchronous rectifier,
inductor, and PC board resistances
• V_DROP2 is the sum of the parasitic voltage drops in the
charging path, including high-side switch, inductor, and PC
board resistances
• t_ON is the on-time calculated by the ISL6237
20
FN6418.4
March 18, 2008