SI3200-X-FS SILABS [Silicon Laboratories], SI3200-X-FS Datasheet - Page 30

• Manufacturer Part Number: SI3200-X-FS
• Manufacturer: SILABS [Silicon Laboratories]

Si3220/25
3.2. Power Supply Sequencing
To ensure proper operation, the following power
sequencing guidelines should be followed:
The Si3200 features an ESD clamp protection circuit
connected between the V
clamp protects the Si3200 against ESD damage when
the device is being handled out-of-circuit during
manufacture. Precautions must be taken in the V
V
V
respective target values in a linear fashion and must not
exhibit fast transients or oscillations which could cause
the ESD clamp to be activated for an extended period of
time resulting in damage to the Si3200. The resistors
shown as R20 through R23 together with capacitors
C23, C24, C30 and C31 on Figure 12 and R23 through
R26 along with capacitors C24, C25, C32 and C33 in
Figure 13 provide some measure of protection against
in-circuit ESD clamp activation by forming a filter time
constant and by providing current limiting action in case
of momentary clamp activation during power-up. These
resistors and capacitors must be included in the
application circuit, while ensuring that the V
V
start-up behavior that is free of undesirable transients or
oscillations. Once the V
state final values, the ESD clamp has circuitry that
prevents it from being activated by transients slower
than 10 V/µs. In the steady powered-up state, the V
and V
resulting in a voltage slew rate greater than 10 V/µs.
3.3. DC Feed Characteristics
The Si3220 and Si3225 offer programmable constant-
voltage and constant-current operating regions as
illustrated in Figure 14. The constant voltage region
(defined
programmable from 0 to 63.3 V in 1 V steps. The
30
BATH
DD
BATH
V
voltage at least 20 ms before V
begin to ramp to its desired voltage.
Transients and oscillations with a dv/dt above 10 V/
µs on the V
avoided.
The ramp-up time for V
2 ms to 20 ms. The ramp-up time for V
be in the range of 10 ms to 150 ms. Slower ramp-up
times are not recommended.
V
V
up.
DD
BATL
BATH
and V
BATH
system power supply design. At power-up, the
system power supplies are designed to exhibit
should be allowed to reach its steady state
rail must never be more negative than the
rail during any part of the power supply ramp-
by
BATH
rails must therefore not exhibit transients
DD
the
rails must ramp-up from 0 V to their
and V
open-circuit
DD
BATH
DD
and V
DD
supplies should always be
should be in the range of
and V
BATH
BATH
voltage,
are in their steady
BATH
is allowed to
BATH
rails. This
V
should
DD
OC
DD
)
and
and
DD
Rev. 1.2
is
constant current region (defined by the loop current
limit, I
0.87 mA steps. The Si3220 and Si3225 exhibit a
characteristic dc impedance of 640 Ω or 320 Ω during
active mode. (See "3.4. Adaptive Linefeed" on page 33).
The TIP-RING voltage (V
programmable voltage (V
voltage headroom to the most positive terminal
(typically the TIP lead in normal polarity or the RING
lead in reverse polarity) for carrying audio signals. A
similar programmable voltage (V
between the most negative terminal and the battery
supply rail for carrying audio signals. (See Figure 14.)
The user-supplied battery voltage must have sufficient
amplitude under all operating states to ensure sufficient
headroom. The Si3200 may be powered by a lower
secondary battery supply (V
dissipation when driving short-loop lengths.
3.3.1. Calculating Overhead Voltages
The two programmable overhead voltages (V
V
V
normal operating conditions, these overhead voltages
are sufficiently low to maintain the desired TIP-RING
voltage (V
under which the user must exercise care in providing a
battery supply with enough amplitude to supply the
required TIP-RING voltage and enough margin to
accommodate these overhead voltages. The V
voltage is programmed for a given operating condition.
Therefore, the open-circuit voltage (V
according to the required overhead voltage (V
the supplied battery voltage (V
pay attention to the maximum V
be required for each operating state.
In the off-hook active state, sufficient V
maintained to correctly power the phone from the
battery supply that is provided. Because the battery
supply depends on the state of the input supply (i.e.,
CM
BAT
Figure 14. DC Linefeed Overhead Voltages
) represent one portion of the total voltage between
and ground as illustrated in Figure 14. Under
LIM
V
) is programmable from 18 to 45 mA in
OC
Secondary V
Constant I Region
V
BATL
). However, there are certain conditions
Selected
V
OV
(Forward State)
BAT
V
CM
OC
Constant V Region
CM
) is offset from ground by a
BATL
Loop Closure Threshold
V
) to provide sufficient
OV
BAT
OV
) to reduce total power
V
OC
). The user should
and V
OV
V
V
V
RING
) is an offset
BATH
TIP
R
LOOP
CM
OC
OC
that might
) varies
must be
OV
OV
) and
and
CM