L6920DTR ,1V HIGH EFFICIENCY SYNCHRONOUS STEP UP CONVERTERFeatures■ 0.6 TO 5.5V OPERATING INPUT VOLTAGE■ 1V START UP INPUT VOLTAGE■ INTERNAL SYNCHRONOUS RECT ..
L6924D013TR ,Single Cell Li Ion battery ChargerFeatures■ Fully integrated solution, with a power MOSFET, reverse blocking diode, sense resistor, a ..
L6926 ,HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS STEP DOWN REGULATORAbsolute Maximum RatingsSymbol Parameter Value UnitV Input voltage -0.3 to 6 V6V Output switching v ..
L6926D1013TR ,HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS STEP DOWN REGULATORElectrical Characteristics (T = 25°C, V = 3.6V unless otherwise specified)j CCSymbol Parameter Test ..
L6926D1013TR ,HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS STEP DOWN REGULATORFEATURES■ 2V TO 5.5V BATTERY INPUT RANGE■ HIGH EFFICIENCY: UP TO 95%■ INTERNAL SYNCHRONOUS SWITCHVF ..
L6928 ,High efficiency monolithic synchronous step down regulatorfeatures and protections . . . 105.1 DROPOUT operation 105.2 PGOOD (Power Good output) ..
LC4128B-10TN100I , 3.3V/2.5V/1.8V In-System Programmable SuperFAST High Density PLDs
LC4128B-75T128C , 3.3V/2.5V/1.8V In-System Programmable SuperFAST High Density PLDs
LC4128B-75TN100C , 3.3V/2.5V/1.8V In-System Programmable SuperFAST High Density PLDs
LC4128C-75T100C , 3.3V/2.5V/1.8V In-System Programmable SuperFAST High Density PLDs
LC4128C-75T100C , 3.3V/2.5V/1.8V In-System Programmable SuperFAST High Density PLDs
LC4128C-75T100I , 3.3V/2.5V/1.8V In-System Programmable SuperFAST High Density PLDs
L6920-L6920DTR
1V HIGH EFFICIENCY SYNCHRONOUS STEP UP CONVERTER
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L6920February 2005
Features 0.6 TO 5.5V OPERATING INPUT VOLTAGE 1V START UP INPUT VOLTAGE INTERNAL SYNCHRONOUS RECTIFIER ZERO SHUT DOWN CURRENT 3.3V AND 5V FIXED OR ADJUSTABLE
OUTPUT VOLTAGE (2V UP TO 5.2V) 120mΩ INTERNAL ACTIVE SWITCH LOW BATTERY VOLTAGE DETECTION REVERSE BATTERY PROTECTION
1.1 Applications ONE TO THREE CELL BATTERY DEVICES PDA AND HAND HELD INSTRUMENTS CELLULAR PHONES - DIGITAL CORDLESS
PHONE PAGERS GPS DIGITAL CAMERAS
DescriptionThe L6920 is a high efficiency step-up controller re-
quiring only three external components to realize the
conversion from the battery voltage to the selected
output voltage.
The start up is guaranteed at 1V and the device is op-
erating down to 0.6V.
Internal synchronous rectifier is implemented with a
120mΩ P-channel MOSFET and, in order to improve
the efficiency, a variable frequency control is imple-
mented.
1V HIGH EFFICIENCY SYNCRONOUS STEP UP CONVERTER
Figure 1. Application CircuitRev. 2
L6920
Table 1. Pin Description
Figure 2. Pin Connection (Top view)
Table 2. Absolute Maximum Ratings
Table 3. Thermal Data
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L6920
Table 4. Electrical Characteristcs (Vin = 2V, FB = GND, Tamb = -40°C to 85°C and Tj < 125°C unless otherwise specified)
L6920
Figure 3. Efficiency vs. Output Current
Figure 4. Efficiency vs. Output Current
Figure 5. Startup Voltage vs Output Current
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L6920 Detailed DescriptionThe L6920 is a high efficiency, low voltage step-up DC/DC converter particularly suitable for 1 to 3 cells (Li-Ion/
polymer, NiMH respectively) battery up conversion.
These performances are achieved via a strong reduction of quiescent current (10µA only) and adopting a syn-
chronous rectification, that implies also a reduced cost in the application (no external diode required).
Operation is based on maximum ON time - minimum OFF time control, tailored by a current limit set to 1A. A
simplified block diagram is shown here below.
Figure 6. Simplified Block Diagram Principle of OperationIn L6920 the control is based on a comparator that continuously checks the status of output voltage.
If the output voltage is lower than the expected value, the control function of the L6920 directs the energy stored
in the inductor to be transferred to the load. This is accomplished by alternating between two basic steps:
- TON phase: the energy is transferred from the battery to the inductor by shorting LX node to ground via the N-
channel power switch. The switch is turned off if the current flowing in the inductor reaches 1A or after a max-
imum on time set to 5µs.
- TOFF phase: the energy stored in the inductor is transferred to the load through the synchronous switch for at
least a minimum off time equal to 1µs. After this, the synchronous switch is turned off as soon as the output
voltage goes lower than the regulated voltage or the current flowing in the inductor goes down to zero.
So, in case of light load, the device works in PFM mode, as shown in figures 7 to 10.
L6920
Figure 7. PFM mode Condition: Vout = 5V; Vin =1.5V.
Trace1: Vout (50mV~/div) Trace 4: IL (100mA/div)
Time div.: 5µs/div
Figure 8. Heavier load - Train pulses overlapping.
Trace1: Vout (100mV~/div) Trace 4: IL (200mA/div)
Time div.: 10 µs/div
Figure 9. Heavy load - Inductor current ripples
below Ilim Trace1: Vout (100mV~/div) Trace 4: IL
(200mA/div) Time div.: 20 µs/div
Figure 10. Heavy load and High ESR. Regulation
falls in continuous mode of operation. Trace1:
Vout (100mV~/div) Trace 4: IL (200mA/div). Time
div.: 5 µs/divWhen Iload is heavier, the pulse trains are overlapped. Figures 7 - 8 show some possible behaviors.
Considering that current in the inductor is limited to 1A, the maximum load current is defined by the following
relationship:
eq. (1)
Where η is the efficiency and Ilim =1A.
Of course, if Iload is greater than Iload_lim the regulation is lost (figure 11). load_liminout
----------- IlimT off min– Vout Vin–⋅--------------------------⋅ ⎝⎠⎛⎞η⋅⋅=
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L6920
Figure 11. No regulation. Iload > Iload_lim
Trace1: Vout (100mV~/div) Trace 4: IL (200mA/div).
Time div.: 5 µs/div
4.1 Start-upOne of the key features of L6920 is the startup at sup-
ply voltage down to 1V (please see the diagram in
Figure 5. in case of heavy load).
The device leaves the startup mode of operation as
soon as VOUT goes over 1.4V. During startup, the
synchronous switch is off and the energy is trans-
ferred to the load through its intrinsic body diode.
The N-channel switches with a very low RDSon
thanks to an internal charge pump used to bias the
power mos gate. Because of this modified behavior,
TON/TOFF times are lengthened. Current limit and
zero crossing detection are still available.
4.2 ShutdownIn shutdown mode (SHDN pulled low) all internal cir-
cuitries are turned off, minimizing the current provid-
ed by the battery (ISHDN < 100 nA, in typical case).
Both switches are turned off, and the low battery
comparator output is forced in high impedance state.
The synchronous switch body diode causes a para-
sitic path between power supply and output that can't
be avoided also in shutdown.
4.3 Low battery detectionThe L6920 includes a low battery detector compara-
tor. Threshold is VREF voltage and a 1.3% hystere-
sis is added to avoid oscillations when input crosses
the threshold slowly. The LBO is an open drain out-
put so a pull up resistor is required for a proper use.
4.4 Reverse polarityA protection circuit has been implemented to avoid
that L6920 and the battery are destroyed in case of
wrong battery insertion.
In addition, this circuit has been designed so that the
current required by the battery is zero also in reverse
polarity.
Application Information
5.1 Output voltage selectionOutput voltage must be selected acting on FB pin.
Three choices are available: fixed 3.3V, 5V or adjust-
able output set via an external resistor divider.
Table 5. Output Voltage Selection
