TDA9115 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TDA9115' PDF : 45 Pages View PDF
TDA9115
certain delay (tBTrigDel / TH) after middle of H-fly-
back. The output is set On at the end of a short
pulse generated by the monostable trigger.
Timing of reset of the R-S flip-flop affects duty cy-
cle of the output square signal and so the energy
transferred from DC/DC converter input to its out-
put. A reset edge is provided by comparator C2 if
the voltage on pin BISense exceeds the internal
threshold VThrBIsCurr. This represents current limi-
tation if a voltage proportional to the current
through the power component or deflection stage
is available on pin BISense. This threshold is af-
fected by the voltage on pin HPosF, which rises at
soft start and descends at soft stop. This ensures
self-contained soft control of duty cycle of the out-
put signal on pin BOut. Refer to Figure 10. Another
condition for the reset of the R-S flip-flop, OR-ed
with the one described before, is that the voltage
on pin BISense exceeds the voltage VC1, which
depends on the voltage applied on input BISense
of the error amplifier O1. The two voltages are
compared, and the reset signal generated by the
comparator C1. The error amplifier amplifies (with
a factor defined by external components) the dif-
ference between the input voltage proportional to
DC/DC convertor output voltage and internal refer-
ence VBReg.
Both step-up (DC/DC converter output voltage
higher than its input voltage) and step-down (out-
put voltage lower than input) are possible.
DC/DC controller Off-to-On edge timing
BOutPh BOHEdge
Timing of Off-to-O n transition
(Sad07/ (Sad17/
on BOut outpu t
D7)
D3)
0
don’t care Middle of H-flyback plus tBTrigDel
1
0
Falling edge of H-drive signal
1
1
Rising edge of H-drive signal
Figure 14. DC/DC converter controller block diagram
BOHEdge
(I2C)
BOutPh
(I2C)
H-drive edge
Monostable
~500ns
H-flyback
(+delay)
I1
VCC
VBReg
Feedback
+
-O1
BRegIn
BComp
VThrBIsCurr
2R R VC1 -
C1
+
-
C2
+
Soft start
I2
N type
S
Q
R
P type
I3
BOutPol
(I2C)
HBOutEn
XRayAlarm
(I2C)
BOut
HPosF
BIsense
32/45
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