Texas Instruments TPS65135 SIMO Converter Evaluation Module TPS65135EVM-265 TPS65135EVM-265 데이터 시트
제품 코드
TPS65135EVM-265
SLVS704A – NOVEMBER 2011 – REVISED NOVEMBER 2011
DETAILED DESCRIPTION
The TPS65135 operates with a four-switch buck-boost converter topology, generating a negative and a positive
output voltage with a single inductor. The device uses the SIMO regulator technology featuring best-in-class line-
transient regulation, buck-boost mode for the positive and negative outputs, and highest efficiency over the entire
load-current range. High efficiency over the entire load-current range is implemented by reducing the converter
switching frequency. Out-of-audio mode avoids the switching frequency going below 20 kHz.
output voltage with a single inductor. The device uses the SIMO regulator technology featuring best-in-class line-
transient regulation, buck-boost mode for the positive and negative outputs, and highest efficiency over the entire
load-current range. High efficiency over the entire load-current range is implemented by reducing the converter
switching frequency. Out-of-audio mode avoids the switching frequency going below 20 kHz.
As illustrated in the
, the converter operates with two control loops. One error
amplifier sets the output voltage for the positive output OUTP. The ground error amplifier regulates FBG to
typically 0 V. Using the external feedback divider allows setting both output voltages, OUTP and OUTN. In
principle the converter topology operates just like any other buck-boost converter topology with the difference
that the output voltage across the inductor is the sum of the positive and negative output voltage. With this
consideration all calculations of the buck-boost converter apply for this topology as well. During the first switch
cycle M1 and M2 are closed, connecting the inductor from VIN to GND. During the second switch cycle the
inductor discharges to the positive and negative outputs by closing switches M4 and M3. Because the inductor is
discharged to both of the outputs simultaneously, the output voltages can be higher or lower than the input
voltage. Because of this the converter operates best when the current out of OUTP is equal to the current flowing
into OUTN. This is for example the case when driving an AMOLED panel. Asymmetries in load current can be
canceled out by the used topology. However this is only possible for current asymmetries of up to 50%. During
light load the converter operates in discontinuous conduction mode. The converter operates in peak-current-
mode control with the switching cycle given by an internal voltage-controlled oscillator (VCO). As the load current
increases the converter operates in continuous-conduction mode. In this mode, the converter moves to peak-
current control with the switch cycle given by the fixed off-time. The SIMO regulator topology has excellent line
transient regulation when operating in discontinuous conduction mode. As the load current increases, entering
continuous conduction mode, the line transient performance is linearly decreased.
typically 0 V. Using the external feedback divider allows setting both output voltages, OUTP and OUTN. In
principle the converter topology operates just like any other buck-boost converter topology with the difference
that the output voltage across the inductor is the sum of the positive and negative output voltage. With this
consideration all calculations of the buck-boost converter apply for this topology as well. During the first switch
cycle M1 and M2 are closed, connecting the inductor from VIN to GND. During the second switch cycle the
inductor discharges to the positive and negative outputs by closing switches M4 and M3. Because the inductor is
discharged to both of the outputs simultaneously, the output voltages can be higher or lower than the input
voltage. Because of this the converter operates best when the current out of OUTP is equal to the current flowing
into OUTN. This is for example the case when driving an AMOLED panel. Asymmetries in load current can be
canceled out by the used topology. However this is only possible for current asymmetries of up to 50%. During
light load the converter operates in discontinuous conduction mode. The converter operates in peak-current-
mode control with the switching cycle given by an internal voltage-controlled oscillator (VCO). As the load current
increases the converter operates in continuous-conduction mode. In this mode, the converter moves to peak-
current control with the switch cycle given by the fixed off-time. The SIMO regulator topology has excellent line
transient regulation when operating in discontinuous conduction mode. As the load current increases, entering
continuous conduction mode, the line transient performance is linearly decreased.
Advanced Power-Save Mode for Light-Load Efficiency
In order to maintain high efficiency over the entire load-current range, the converter reduces its switching
frequency as the load current decreases. The advanced power-save mode controls the switching frequency
using a voltage-controlled oscillator (VCO). The VCO frequency is proportional to the inductor peak current, with
a lower frequency limit of 20 kHz in typical applications the frequency does not go below 100 kHz. This avoids
disturbance of the audio band and minimizes audible noise coming from the ceramic input and output capacitors.
By maintaining a controlled switching frequency, possible EMI is minimized. This is especially important when
using the device in mobile phones. See
frequency as the load current decreases. The advanced power-save mode controls the switching frequency
using a voltage-controlled oscillator (VCO). The VCO frequency is proportional to the inductor peak current, with
a lower frequency limit of 20 kHz in typical applications the frequency does not go below 100 kHz. This avoids
disturbance of the audio band and minimizes audible noise coming from the ceramic input and output capacitors.
By maintaining a controlled switching frequency, possible EMI is minimized. This is especially important when
using the device in mobile phones. See
for typical switching frequency versus load current. For zero
load an internal shunt regulator ensures stable output voltage regulation.
Buck-Boost Mode Operation
Buck-boost mode operation allows the input voltage to be higher or lower than the output voltage. This mode
allows the use of batteries and supply voltages that are above the output voltage of OUTP.
allows the use of batteries and supply voltages that are above the output voltage of OUTP.
Inherent Excellent Line-Transient Regulation
The SIMO regulator achieves inherent superior line-transient regulation when operating in discontinuous
conduction mode, shown in
conduction mode, shown in
and
. In discontinuous conduction mode the current delivered to the
output is given by the inductor peak current and falling slope of the inductor current. This is shown in
,
where the output current, given by the area A, is the same for different input voltages. Because the converter
uses peak-current-mode control, the peak current is fixed as long as the load current is fixed. The falling slope of
the inductor current is given by the sum of the output voltage and inductor value. This is also a fixed value and
independent of the input voltage. Because of this, any change in input voltage changes the converter duty cycle
but does not change the inductor peak current or the falling slope of the inductor current. Therefore the output
current, given by the area A (
uses peak-current-mode control, the peak current is fixed as long as the load current is fixed. The falling slope of
the inductor current is given by the sum of the output voltage and inductor value. This is also a fixed value and
independent of the input voltage. Because of this, any change in input voltage changes the converter duty cycle
but does not change the inductor peak current or the falling slope of the inductor current. Therefore the output
current, given by the area A (
), remains constant over any input voltage variation. Because the area A
is constant, the converter has an inherently perfect line regulation when operating in discontinuous conduction
mode. Entering continuous conduction mode (CCM) linearly decreases the line-transient performance. However
the line-transient response in CCM is still as good as for any standard current-mode-controlled switching
converter. The following formulas detail the relations of the TPS65135 converter topology operating in CCM.
mode. Entering continuous conduction mode (CCM) linearly decreases the line-transient performance. However
the line-transient response in CCM is still as good as for any standard current-mode-controlled switching
converter. The following formulas detail the relations of the TPS65135 converter topology operating in CCM.
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