TDA9112A View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TDA9112A' PDF : 60 Pages View PDF
TDA9112A
internal reference and so the output voltage is I²C-
bus adjustable by means of BREF I²C-bus control.
Both step-up (DC/DC converter output voltage
higher than its input voltage) and step-down (out-
put voltage lower than input) can be built.
9.7.1 Synchronization of DC/DC controller
For sake of application flexibility, the output drive
signal on BOut pin can be synchronized with one of
four events in Table 9. For the first line case, the
synchronization instant is every second top of hor-
izontal VCO saw tooth. See Figure 7.
9.7.2 Soft-start and soft-stop on B-drive
The soft-start and soft-stop procedure is carried
out at each switch-on or switch-off of the B-drive
signal, either via HBOutEn I²C-bus bit or after re-
set of XRayAlarm I²C-bus flag, to protect external
power component. See Figure 10 and sub chapter
Safety functions on page 50.
The drive signal on BOut pin can be switched off
alone by means of BMute I²C-bus bit, without
switching off the drive signal on pin HOut. The
switch-off is quasi-immediate, without the soft-stop
procedure. At switching back on, the soft-start of
the DC/DC controller is performed, timed by an in-
ternal timing circuit, see Figure 18.
When BSafeEn I²C-bus bit is enabled, the drive
signal on BOut pin will go off as soon as the hori-
zontal PLL1 indicates unlocked state, without the
soft-stop. Resuming of locked state will initiate the
soft-start mechanism of the DC/DC controller,
timed by an internal timing circuit.
Table 9. IDC/DC controller Off-to-On edge timing
BOutPh
(Sad07h/D7)
BOHEdge
(Sad17h/D3)
Timing of Off-to-On transition on BOut output
0
1
VCO ramp top at Horizontal frequency divided by two
0
0
Middle of H-flyback plus tBTrigDel
1
0
Falling edge of H-drive signal
1
1
Rising edge of H-drive signal
Figure 18. DC/DC converter controller block diagram
H-drive edge
H-fly-back
(+delay)
0
1
BOHEdge
(I²C)
0
BOutPh
(I²C)
1
Monostable
~500ns
0
VCO
÷2
VBReg
Feedback
+
15 -O1
BRegIn
1
2R R
VC2
-
C1
+
14
BComp
VThrBIsCurr
Safety block Soft start
10
HPosF
-
C2
+
+
C3
-
16
BISense
timing
I1
VCC
I2
N type
S
Q
R
P type
I3
BOutPol
(I²C)
B-drive inhibition
(safety functions)
28
BOut
B-drive protection at H-unlock
(safety functions)
49/60
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