Theory of operation

STHVDAC-253MTG

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DocID027917 Rev 4

3.1.2

DAC operation in turbo mode -- glide_enable = 0b, turbo_mode = 1b

A specific turbo mode is implemented in the STHVDAC-253MTG to ensure a fast system

settling time.

In this mode, the DAC voltage outputs are optimized to minimize the settling time on the

output capacitor reaches its final value within 55µs typical.

In turbo mode, STHVDAC-253MTG has been optimized to support up to 4 different output

RC loads, as defined in Table 6. The RC loads can be selected for each output

independently, by controlling PTIC_selection bits in registers#9 to 11.

Typical timing diagram in turbo mode is shown on Figure 4.

3.1.3

DAC operation in glide mode - glide_enable = 1b, turbo_mode = x

Glide mode has been implemented to smooth DAC output voltage transition, and to

minimize the impact of tunable capacitor changes on RF system performance (especially to

meet 3GPP phase discontinuity requirements).

In this mode, the DAC output voltage transitions from old to new voltage value, in a period of

time equal to the glide_delay defined as :

Glide_delay = glide_step_delay * 256 (programmable from 512 µs up to 16.84 ms)

glide_step_delay defined in registers#1 and 5 as per Table 11.

Typical timing diagram in glide mode is shown on Figure 4.

Table 6. Supported output RC loads (turbo mode only)

PTIC_selection bits

Rload

Cload

00

12 kΩ

2.7 nF

01

17 kΩ

2.7 nF

10

22 kΩ

2.7 nF

11

27 kΩ

2.7 nF