Datasheet

TPS53313
SLUSAS8 –DECEMBER 2011 www.ti.com
DETAILED DESCRIPTIONS
OVERVIEW
The TPS53313 is a high-efficiency switching regulator with two integrated N-channel MOSFETs and is capable
of delivering up to 6 A of load current. The TPS53316 provides output voltage from 0.6 V up to 0.7 × V
IN
from
4.5V to 16 V wide input voltage range. The output voltage accuracy is better than ±1% over load, line, and
temperature.
This device can operate in either forced continuous conduction mode (FCCM) or skip mode with selectable
soft-start time to fit various application needs. Skip mode operation provides reduced power loss and increases
the efficiency at light load. The unique, patented PWM modulator enables smooth light load to heavy load
transition while maintaining fast load transient.
OPERATION MODE
The TPS53313 has 6 operation modes determined by the MODE/SS pin connection as listed in Table 1. The
current limit thresholds and associated capacitance selections are shown in Table 2 .
Table 1. Operation Mode Selection
MODE/SS PIN OPERATION t
SS
SOFT-START
CONNECTION MODE TIME (ms)
10 kΩ to GND FCCM 6
20 kΩ to GND FCCM 3
39 kΩ to GND FCCM 1
82 kΩ to GND Skip Mode 6
160 kΩ to GND Skip Mode 3
Floating Skip Mode 1
Table 2. Capacitor Selection
CURRENT LIMIT
MODE/SS PIN SETTING (nF)
THRESHOLD (A)
No Capacitor 6
2.2 4.5
10 9
In forced continuous conduction mode (FCCM), the high-side FET is ON during the on-time and low-side FET is
ON during the off-time. The switching is synchronized to the internal clock thus the switching frequency is fixed.
In this mode, the switching frequency remains constant over the entire load range which is suitable for
applications that need tight control of switching frequency.
In skip mode, the high-side FET is on during the on-time and low-side FET is on during the off-time until the
inductor current reaches zero. An internal zero-crossing comparator detects the zero crossing of inductor current
from positive to negative. When the inductor current reaches zero, the comparator sends a signal to the logic
control and turns off the low-side FET. The on-pulse in skip mode is designed to be 25% higher than CCM to
provide hysteresis to avoid chattering between CCM and skip mode.
Also, the overcurrent protection threshold can be set to 4.5 A, 6 A or 9 A by changing the capacitor that is in
parallel with MODE/SS pin. Specifically, a 6-A current limit threshold is set without an external capacitor, the 4.5
A current limit threshold is set with a 2.2-nF capacitor, and the 9-A current limit threshold is set when a 10-nF
capacitor is in parallel with MODE/SS pin.
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