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PDF ZXSC100 Data sheet ( Hoja de datos )
| Número de pieza | ZXSC100 | |
| Descripción | SINGLE CELL DC-DC CONVERTER SOLUTION | |
| Fabricantes | Diodes | |
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ZXSC100X8 Obsolete
Closest Alternative is ZXSC100N8
ZXSC100
SINGLE CELL DC-DC CONVERTER SOLUTION
Description
The ZXSC100 series is designed for DC-DC applications
where step-up voltage conversion from very low input
voltages is required. These applications mainly operate from
single nickel cadmium or nickel metal hydride battery cells.
The circuit can start up under full load with regulation
maintained down to an input voltage of only 0.926 volts. The
solution configuration ensures optimum efficiency over a wide
range of load currents. Several circuit configurations are
possible with loads up to 2W. The step up output voltage is
easily programmed with external resistors. With its non-
synchronous architecture an output voltage down to the input
voltage level can be achieved. For best performance the
ZXSC100 quiescent current is a small 150μA ensuring
minimum battery drain in no load conditions.
The IC and discrete combination offers the ultimate cost vs.
performance solution for single cell DC-DC conversion.
Pin Assignments
SO-8
Features
• Efficiency maintained over a wide range of input
voltages and load currents 82% efficiency @ VBATT = 1V
• Startup under full load
• Minimum operating input voltage VBATT = 0.926V
• Adjustable output voltage down to VBATT
• Quiescent current typically 150μA referred to input
voltage
• SO-8 package in “Green” Molding Compound (No Br,
Sb) with lead Free Finish/RoHS Compliant (Note 1)
Notes:
1. EU Directive 2002/95/EC (RoHS). All applicable RoHS
exemptions applied. Please visit our website at:
http://www.diodes.com/products/lead_free.html
Typical Application Circuit
Applications
• Cordless telephones
• MP3 players
• PDA
• Pagers
• Battery backup supplies
• Electronic toothbrush
• GPS receivers
• Digital camera
• Palmtop computers
• Hand held instruments
• Portable medical equipment
• Solar powered equipment
ZXSC100
Document number: DS33613 Rev. 6 - 2
1 of 13
www.diodes.com
January 2012
© Diodes Incorporated
1 page  
ZXSC100X8 Obsolete
Closest Alternative is ZXSC100N8
ZXSC100
SINGLE CELL DC-DC CONVERTER SOLUTION
Device Description
The ZXSC100 is non-synchronous PFM, DC-DC controller IC which, when combined with a high performance external
transistor, enables the production of a high efficiency boost converter for use in single cell applications. A block diagram is
shown for the ZXSC100 on page 2.
A shutdown circuit turns the device on or off at VCC = 1V with a hysteresis of typically 80mV. At start up, comparator Comp1
turns the driver circuit and therefore the external switching transistor on. This circuit will remain active until the feedback
voltage at the pin FB rises above VREF, which is set to 730mV. An external resistive divider on the FB pin sets the output
voltage level.
Comparator Comp2 forces the driver circuit and the external switching transistor off, if the voltage at ISENSE exceeds 25mV.
The voltage at ISENSE is taken from a current sense resistor connected in series with the emitter of the switching transistor.
A monostable following the output of Comp2 extends the turn-off time of the output stage by a minimum of 2µs. This ensures
that there is sufficient time to discharge the inductor coil before the next on period. The AND gate between the monostable
and Comp1 output ensures that the switching transistor always remains on until the ISENSE threshold is reached and that the
minimum discharge period is always asserted. The pulse width is constant, the pulse frequency varies with the output load.
The driver circuit supplies the external switching transistor with a defined current, which is programmed by an external
resistor connected between the RE pin and VCC. The internal reference voltage for the circuit is 25mV below VCC. To
maximise efficiency the external transistor is switched quickly, typically being forced off within 20ns.
In higher power applications more current can be supplied to the switching transistor by using a further external component.
The driver transistor in the IC can be bypassed with the addition of a discrete PNP. More information on this circuit
configuration can be found in the applications section.
ZXSC100
Document number: DS33613 Rev. 6 - 2
5 of 13
www.diodes.com
January 2012
© Diodes Incorporated
5 Page 
ZXSC100X8 Obsolete
Closest Alternative is ZXSC100N8
ZXSC100
SINGLE CELL DC-DC CONVERTER SOLUTION
Designing with the ZXSC100 (cont.)
Main Switching Waveforms (cont.)
Fig. 8 Diode Current (200mA/div)
Fig. 9 Output Voltage Ripple for
3.3V/100mA output
Output Voltage Ripple
Output voltage ripple is shown in Figure 9. The circuit is operated with a 1.2V input voltage, 3.3V output voltage and 100mA
load current. Output voltage ripple will be dependent, to a large extent, on the output capacitor ESR. (see Applications section
for recommended capacitors).
Transient Response
Transient response to step changes in load is a critical feature in many converter circuits. The ZXSC100 operates a pulse by
pulse regulation scheme and therefore corrects for changes in the output every pulse cycle, giving excellent response
characteristic.
Measurement with a Power Supply
When measuring with a power supply it is important to realise that the impedance is much greater than that of a secondary
battery (NiCd or NiMH). To simulate the lower impedance of the battery x10 low ESR 1000µF capacitors where placed in
parallel at the input of the converter. All the dynamic performance measurements were taken using this technique.
ZXSC100
Document number: DS33613 Rev. 6 - 2
11 of 13
www.diodes.com
January 2012
© Diodes Incorporated
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet ZXSC100.PDF ] | |
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