TPS82690_15 Datasheet, PDF (15/26 Pages) Texas Instruments – 500-mA, HIGH-EFFICIENCY MicroSiP™ STEP-DOWN CONVERTER (PROFILE <1mm)

www.ti.com
TPS82690
TPS82695
TPS82697
SLVSA66B – JUNE 2011 – REVISED FEBRUARY 2012
DETAILED DESCRIPTION
OPERATION
The TPS8269xSIP is a standalone synchronous step-down converter operating at a regulated 4-MHz frequency
pulse width modulation (PWM) at moderate to heavy load currents (up to 500mA output current). At light load
currents, the TPS8269xSIP's converter operates in power-save mode with pulse frequency modulation (PFM).
The converter uses a unique frequency locked ring oscillating modulator to achieve best-in-class load and line
response. One key advantage of the non-linear architecture is that there is no traditional feed-back loop. The
loop response to change in V_O is essentially instantaneous, which explains the transient response. Although this
type of operation normally results in a switching frequency that varies with input voltage and load current, an
internal frequency lock loop (FLL) holds the switching frequency constant over a large range of operating
conditions.
Combined with best in class load and line transient response characteristics, the low quiescent current of the
device (ca. 24μA) allows to maintain high efficiency at light load, while preserving fast transient response for
applications requiring tight output regulation.
The TPS8269xSIP integrates an input current limit to protect the device against heavy load or short circuits and
features an undervoltage lockout circuit to prevent the device from misoperation at low input voltages.
POWER-SAVE MODE
If the load current decreases, the converter will enter Power Save Mode operation automatically. During
power-save mode the converter operates in discontinuous current (DCM) with a minimum of one pulse, which
produces low output ripple compared with other PFM architectures.
When in power-save mode, the converter resumes its operation when the output voltage trips below the nominal
voltage. It ramps up the output voltage with a minimum of one pulse and goes into power-save mode when the
output voltage is within its regulation limits again.
PFM mode is left and PWM operation is entered as the output current can no longer be supported in PFM mode.
As a consequence, the DC output voltage is typically positioned ca. 1.5% above the nominal output voltage and
the transition between PFM and PWM is seamless.
PFM Mode at Light Load
PFM Ripple
Nominal DC Output Voltage
PWM Mode at Heavy Load
Figure 33. Operation in PFM Mode and Transfer to PWM Mode
Copyright © 2011–2012, Texas Instruments Incorporated
Submit Documentation Feedback
15
Product Folder Link(s): TPS82690 TPS82695 TPS82697