SAA8200HL Datasheet, PDF (49/71 Pages) NXP Semiconductors – Ensation Base integrated wireless audio baseband

Philips Semiconductors
SAA8200HL
Ensation Base integrated wireless audio baseband
See Figure 18 for a coil current cycle in ramp-up mode. The controller enters this mode
when there is an increased demand for energy (voltage falls to below the lower limit). By a
one-time increase of t1 the coil current is increased to a higher average.
I_L
(A)
t1
t2
t1
t2
t1
t (s)
t2
t1
t2
t1
t2
001aac006
Fig 18. Coil current cycle in ramp-up mode
See Figure 19 for a coil current cycle in discontinuous mode. In this mode the coil current
does not flow continuously. Dependent on energy demand a cycle is generated. So
instead of changing the duty cycle as in continuous mode the frequency is changed. This
mode is intended for low power operation. During the first phase the battery ramps up the
current from zero and during the second phase it is ramped down to zero by the load. The
coil current is made to decrease to zero by opening both switches shortly before the
current reaches zero. The moment when the switches are to be closed is learned from the
behavior of the DC-to-DC converter in continuous mode.
I_L
(A)
t1
t2
Fig 19. Coil current cycle in discontinuous mode
t (s)
t1
t2
001aac007
SAA8200HL_2
Preliminary data sheet
Rev. 02 — 17 October 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
49 of 71