ST92196A STMicroelectronics, ST92196A Datasheet - Page 212

• Manufacturer Part Number: ST92196A
• Description: 8/16-bit Mcu For Tv Applications With Up To 96k Rom, On-screen-display And 1 Or 2 Data Slicers
• Manufacturer: STMicroelectronics

VOLTAGE SYNTHESIS (Cont’d)
BRM Generation
The BRM bits allow the addition of a pulse to wid-
en a standard PWM pulse for specific PWM cy-
cles. This has the effect of “fine-tuning” the PWM
Duty cycle (without modifying the base duty cycle),
thus, with the external filtering, providing additional
fine voltage steps.
The incremental pulses (with duration of T
4) are added to the beginning of the original PWM
pulse and thus cause the PWM high time to be ex-
tended by this time with a corresponding reduction
in the low time. The PWM intervals which are add-
ed to are specified in the lower 7 bits of the tuning
word and are encoded as shown in the following
table.
Figure 94. Simplified Filtered Voltage Output Schematic with BRM added
PWMOUT
VOLTAGE
OUTPUT
V
V
0V
0V
DD
DD
=
EXTENDED PULSE
BRM
- VOLTAGE SYNTHESIS TUNING CONVERTER (VS)
INTCLK
T
INTCLK
/
=
/4
Table 44. 7-Bit BRM Pulse Addition Positions
The BRM values shown may be combined togeth-
er to provide a summation of the incremental pulse
intervals specified.
The pulse increment corresponds to the PWM res-
olution.
Fine Tuning
0000001
0000010
0000100
0001000
0010000
0100000
1000000
=
No. of Pulses added at the
following Cycles
8, 24,... 104, 120
4, 12,... 116, 124
2, 6,... 122, 126
1, 3,... 125, 127
16, 48, 80, 112
32, 96
64
BRM = 1
BRM = 0
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