Datasheet

TPS62350, TPS62351
TPS62352, TPS62353
TPS62354, TPS62355, TPS62356
SLVS540E – MAY 2006 – REVISED APRIL 2008 .............................................................................................................................................................. www.ti.com
In multiple-step mode, PWROK is defined as low while the output voltage is ramping up or down. Under all other
operating conditions, PWROK is defined to be low when the output voltage is below -1.5% of the target value.
Voltage Ramp Control
The TPS6235x offers a voltage ramp rate control that can operate in two different modes:
• Multiple-Step Mode
• Single-Step Mode
The mode is selected via DEFSLEW control bits in the CONTROL2 register.
Single-Step Voltage Scaling Mode (default), DEFSLEW[2:0] = [111]
In single-step mode, the TPS6235x ramps the output voltage with maximum slew-rate when transitioning
between the floor and the roof voltages (switch to a higher voltage).
When switching between the roof and the floor voltages (transition to a lower voltage), the ramp rate control is
dependent on the mode selection (see CONTROL1 register) associated with the target register (Forced PWM,
Fast, or Light PFM).
Table 3 shows the ramp rate control when transitioning to a lower voltage with DEFSLEW set to immediate
transition.
Table 3. Ramp Rate Control vs. Target Mode
Mode Associated with HW_nSW Output Voltage Ramp Rate
Target Voltage
Forced PWM X Immediate
Fast PFM X Time to ramp down depends on output capacitance and load current
Light PFM X Time to ramp down depends on output capacitance and load current
For instance, when the output is programmed to transition to a lower voltage with Light or Fast PFM operation
enabled, the TPS6235x ramps down the output voltage without controlling the ramp rate or having intermediate
micro-steps. The required time to ramp down the voltage depends on the capacitance present at the output of
the TPS6235x and on the load current. From an overall system perspective, this is the most efficient way to
perform dynamic voltage scaling.
Multiple-Step Voltage Scaling Mode, DEFSLEW[2:0] = [000] to [110]
In multiple-step mode the TPS6235x controls the output voltage ramp rate regardless of the HW_nSW bit and of
the mode of operation (e.g. Forced PWM, Fast PFM, or Light PFM). The voltage ramp control is done by
adjusting the time between the voltage micro-steps.
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Product Folder Link(s): TPS62350, TPS62351 TPS62352, TPS62353 TPS62354, TPS62355, TPS62356