Philips Semiconductors
Product specification
I2C-bus autosync deflection controller for
PC monitors
TDA4856
Start-up procedure
VCC < 8.3 V:
START
• As long as the supply voltage is too low for correct
operation, the IC will give no acknowledge due to
internal Power-on reset (POR)
Power-down mode (XXXX XXXX)
L1
L2
no acknowledge is given by IC
all register contents are random
• Supply current is 9 mA or less.
V
> 8.3 V
VCC > 8.3 V:
CC
• The internal POR has ended and the IC is in standby
Standby mode (XXXX XX01)
mode
STDBY = 1
SOFTST = 0
• Control bits STDBY and SOFTST are reset to their start
all other register contents are random
values
• All other register contents are random
• Pin HUNLOCK is at HIGH-level.
Setting control bit STDBY = 0:
S
8CH
A
1AH
A
00H
A P
Protection mode (XXXX XX00)
• Enables internal power supply
STDBY = 0
SOFTST = 0
all other register contents are random
• Supply current increases from 9 to 70 mA
• When VCC < 8.6 V register SOFTST cannot be set by
the I2C-bus
S
8CH
A
SAD
A
DATA A P
• Output stages are disabled, except the vertical output
• Pin HUNLOCK is at HIGH-level.
Protection mode (XXXX XX00)
Setting all registers to defined values:
STDBY = 0
SOFTST = 0
• Due to the hardware configuration of the IC
(no auto-increment) any register setting needs a
complete 3-byte I2C-bus data transfer as follows:
START - IC address - subaddress - data - STOP.
registers are pre-set
no
all registers defined?
yes
Setting control bit SOFTST = 1:
L3
S
8CH
A
1AH
A
02H
A P
• Before starting the soft-start sequence a delay of
minimum 80 ms is necessary to obtain correct function
of the horizontal drive
Soft-start sequence (XXXX XX10)
• HDRV duty cycle increases
• BDRV duty cycle increases
• PLL1 and PLL2 are enabled.
STDBY = 0
SOFTST = 1
Operating mode (XXXX XX10)
IC in full operation:
STDBY = 0
SOFTST = 1
• Pin HUNLOCK is at LOW-level when PLL1 is locked
• Any change of the register content will result in
immediate change of the output behaviour
no
no
change/refresh of data?
yes
SOFTST = 0?
yes
• Setting control bit SOFTST = 0 is the only way (except
power-down via pin VCC) to leave the operating mode.
(1)
L4
S
8CH
A
SAD
A
DATA A P
Soft-down sequence:
MGL791
• See L4 of Fig.19 for starting the soft-down sequence.
(1) See Fig.19.
Fig.18 I2C-bus flow for start-up.
1999 Jul 13
37
NXP [ NXP ]
