ZXSC100X8 and ZXSC100N8 OBSOLETE - No Alternative

Document overview

  • Manufacturer or author: Diodes Incorporated
  • PDF pages: 13

Technical content

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)

Applications

  • Cordless Telephones
  • MP3 Players
  • PDAs
  • Pagers
  • Battery Backup Supplies
  • Electronic Toothbrush
  • GPS Receivers
  • Digital Camera
  • Palmtop Computers
  • Handheld Instruments
  • Portable Medical Equipment
  • Solar-Powered Equipment Typical Application Circuit ZXSC100 Document number: DS33613 Rev. 7 - 4 1 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Pin Descriptions Pin No. Name Description 1 EM Emitter of internal drive transistor. Connect to RE in lower power applications. Must be unconnected in higher power applications. 2 BAS Only used if increased drive current to the main external NPN switching transistor is required. (Note 2) 3 RE Drive current sense input. Internal threshold voltage set 25mV below VCC. Connected external sense resistor. (Note 2) 4 VCC Supply voltage, generally NiMH, NiCd single cell. 5 ISENSE Inductor current sense input. Internal threshold voltage set to 25mV. Connect external sense resistor. 6 FB Feedback sense. Internal threshold set to 730mV. Connect external resistive divider to output voltage.

7 GND Ground

8 VDRIVE Drive output for external switching transistor. Connect to base of external bipolar transistor. For increased drive current, see Note 2 Note: 2. In higher load current applications an additional PNP can be used to increase the drive current of the main external NPN switching transistor. The PNP base should be connected to BAS pin, its emitter to the RE pin and its collector connected to V DRIVE pin. Functional Block Diagram Absolute Maximum Ratings Description Rating Unit Supply Voltage 0.3 to 3.5 V Maximum Voltage Other Pins 0.3 to VCC +0.3 V Power Dissipation (25°C) SO-8 780 mW Operating Temperature 0 to 70 °C Storage Temperature -55 to +150 °C Junction Temperature 150 °C ZXSC100 Document number: DS33613 Rev. 7 - 4 2 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Operating Conditions Symbol Parameter Min Typ. Max Unit FOSC Recommended operating frequency (Note 3) — — 200 kHz Note: 3. Operating frequency is application circuit dependent. See application section. Electrical Characteristics (TA = 25°C, VCC = 1.2V; unless otherwise specified) Symbol Parameter Conditions Min Typ Max Units ICC Quiescent current Not switching — 150 200 µA IDRIVE Base drive current VRE = VCC 5 — 10 mA VDRIVE VDRIVE o/p voltage VRE = VCC, IDRIVE = 5mA VCC – 0.17 — — V VFB Feedback voltage — 708 730 752 mV VISENSE Output current reference voltage — 12 17.5 24 mV TCVISENSE ISENSE voltage temp co. — — 0.4 — %/°C VDREF Drive current reference voltage Measured with respect to VCC 20 30 40 mV TCVDREF VDREF temp co. — — 1 — %/°C VCC(SRT) Startup voltage Any output load 1.01 1.06 1.1 V VCC(MIN) Minimum operating input voltage — 0.926 0.98 1 V VCC(HYS) Supply start up to shutdown hysteresis — — 80 — mV IFB Feedback input current — — 100 200 nA ISENSE ISENSE input current VISENSE = 0V 3 4 5.5 µA VO(MIN) Minimum output voltage — VCC — — V VO(MAX) Maximum output voltage FMMT617 as pass element (Note 4) — — 20 V TOFF Discharge pulse width — 1.7 3 µs Note: 4. Depends on breakdown voltage of pass device. Se e FMMT617 datasheet. ZXSC100 Document number: DS33613 Rev. 7 - 4 3 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Typical Characteristics ZXSC100 Document number: DS33613 Rev. 7 - 4 4 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Device Description The ZXSC100 is non -synchronous PFM, DC-DC controller IC, which enables the production of a high -efficiency boost converter for use in single-cell applications when combined with a high-performance external transistor. A block diagram is shown for the ZXSC100 on page 2. A shutdown circuit turns the device on or off at V CC = 1V with a hysteresis of typically 80mV. At start up, comparator Comp1 turns the driver circuit and there by 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 I SENSE 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 outpu t ensures that the switching tr ansistor always remains on until the I SENSE 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 tran sistor 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 V CC. 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 informati on on this circuit configuration can be found in the applications section. ZXSC100 Document number: DS33613 Rev. 7 - 4 5 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED

Application Information

The following section is a design guide for optimum converter performance. Switching Transistor Selection The choice of switching transistor has a maj or impact on the DC-DC converter efficiency. For optimum performance, a bipolar transistor with low VCE(SAT) and high gain is required. The majority of losses in the transistor are on- state and can be calculated by using the following formula: From the calculations above the impact on converter efficiency can be seen. External Drive Transistor Selection For higher-power applications an external transistor is required to provide the additional base drive current to the main switching tran sistor. For this, any small signal PNP transistor is sufficient. See reference designs for recommended part numbers. Schottky Diode Selection As with the switching transistor the Schottky rectifier diode has a major impact on the DC -DC converter efficiency. A Schottky diode with a low forward voltage and fast recovery time must be used for this application. The majority of losses in the diode are on -state and can be calculated by using the formula: The diode must be selected, so the maximum forward current is greater or equal to the maximum peak current in the inductor, and the maximum reverse voltage is greater or equal to the output voltage. The Diodes ZHCS1000 meets these requirements . A datasheet for the ZHCS1000 is available on the Diodes website. Outline information is included in the characteristics section of this datasheet. The inductor value must be chosen to satisfy performance, cost , and size requirements of the overall solution. For the reference designs we recommend an inductor value of 22μH with a core saturation current rating greater than the converter peak current value. Inductor selection has a significant impact on the converter efficiency. For applications where efficiency is critical, a 5% improvement can be achieved with a high-performance inductor. This should be selected with a core saturation current rating much higher than the peak current of the converter— say three times greater. The resultant reduction in core losses brings about the efficiency improvement. Peak Current Definition The peak current rating is a design parameter with a value dependent upon the overall application. For the reference designs, a peak current of 1.2A was chosen to ensure that the converter could provide the required output power. In general, the I PK value must be c hosen to ensure that the switching transistor, Q1, is in full saturation with maximum output power conditions, which assumes worse-case input voltage and transistor gain under all operating temperature extremes. Once IPK is decided the value of R SENSE can be determined by: ZXSC100 Document number: DS33613 Rev. 7 - 4 6 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Application Information (continued) Output Power Definition By making the above assumptions for the inductor and IPK, the output power can be determined by: Note: VOUT = output voltage + rectifier diode VF Figure 1 shows the discontinuous inductor current and the relationship between output power, TON, TDIS, and TOFF. Fig. 1 Discontinuous Inductor Current Output Capacitors Output capacitors are a critical choice in the overall performance of the solution. They are required t o filter the output and supply load transient currents. There are three parameters that are paramount in the selection of the output capacitors their capacitance value, IRIPPLE, and ESR. The capacitance value is selected to meet the load transient requirem ents. The capacitors IRIPPLE rating must meet or exceed the current ripple of the solution. The ESR of the output capacitor can also affect loop stability and transient performance. The capacitors selected for the solution and indicated in the reference designs are optimized to provide the best overall performance. Input Capacitors The input capacitor is chosen for its voltage and RMS current rating. The use of low-ESR electrolytic or tantalum capacitors is recommended. Capacitor values for optimum performance are suggested in the reference design section. Also note that the ESR of the input capacitor is effectively in series with the input and contributes to efficiency losses in the order of I RMS 2 × ESR. ZXSC100 Document number: DS33613 Rev. 7 - 4 7 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Application Information (cont.) Output Voltage Adjustment The ZXSC100 is an adjustable converter that allows the end user the maximum flexibility in output voltage selection. For adjustable operation a potential divider network is connected as indicated in the diagram. The output voltage is determined by the following equation: VOUT = VFB (1 + RA / RB) Where VFB = 730mV The resistor values, RA and RB, must be maximized to improve efficiency and decrease battery drain. Optimisation can be achieved by providing a minimum current of IFB(MAX) = 200nA t o the V BATT pin. The output is adjustable from V FB to the (BR)V CEO of the switching transistor, Q1. Note: For the reference designs, RA is assigned the label R3 and RB the label R4. External Transistor Base Drive Selection Optimization of the external switching transistor base drive can be necessary for improved efficiency in low -power applications. This can be achieved by introducing an external resistor between the supply and the RE pin of the ZXSC100. The resistor value can be determined by: Layout Issues Layout is critical for the circuit to function optimally in terms of electrical efficiency, thermal considerations, and noise. For step- up converters there are four main current loops: the input loop, power -switch loop, rectifier loop , and output loop. The supply charging the input capacitor forms the input loop. The power -switch loop is defined when Q1 is on, current flows from the input through the inductor, Q1, R SENSE, and to ground. When Q1 is off , the energy stored in the inductor is transferred to the output capacitor and loaded through D1, which forms the rectifier loop. The output loop is formed by the output capacitor supplying the load when Q1 is switched back off. To optimize for best performance each of these loops must be kept separ ate from each other and interconnections made with short, thick traces thus minimizing parasitic inductance, capacitance, and resistance. Also the sense resistor R2 must be connected, with minimum trace length, between emitter lead of Q1 and ground—again m inimizing stray parasitics. ZXSC100 Document number: DS33613 Rev. 7 - 4 8 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Designing with the ZXSC100 Introduction This section refers to the ZXSC100, 3.3V/100mA output reference design and demonstrates the dynamic performance of the solution. Fig. 2 ZXSC100 Low-Power Solution, 3.3V/100mA Output Efficiency Efficiency is often quoted as one of the key parameters of a DC-DC converter. Not only does it give an instantaneous idea of heat dissipation but also an idea as to the extent battery life can be extended. Figure 3 shows the efficiency of the ZXSC100 low-power solution. Efficiency vs output current is shown for a 3.3V output at various input voltages. Fig. 3 ZXSC100 Efficiency vs Output Current ZXSC100 Document number: DS33613 Rev. 7 - 4 9 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Designing with the ZXSC100 (continued) Main Switching Waveforms Steady-state operation under constant load gives an excellent indication of ZXSC100 performance. The main switching waveform, measured at the collector of Q1, indicates the transistor on-state and the diode energy transfer to the output (as shown in Figure 4). Fig. 4 Switching Waveform Fig. 5 ISENSE Threshold The peak switching current is derived from the threshold of the I SENSE pin and the sense resistor value (see applications se ction for calculations). Figure 5. shows the switching waveform associated with the ISENSE pin. Figure 6 shows the discontinuous inductor current. The ramp- up current stores energy in the inductor. The switching transistor,Q1, is on during this time and has an equivalent current ramp -up, shown in Figure 7. The ramp- down current is associated with the energy being delivered to the output from the Schottky diode, D1. The diode current is equivalent to this ramp-down current and is shown in Figure 8. Fig. 6 Inductor Current (200mA/div) Fig. 7 Transistor Current (200mA/div) ZXSC100 Document number: DS33613 Rev. 7 - 4 10 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED Designing with the ZXSC100 (cont.) Main Switching Waveforms (continued) 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 is 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 criti cal 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 ten low-ESR 1000µF capacitors were placed in parallel at the input of the converter. All the dynamic performance measurements were taken using this technique. ZXSC100 Document number: DS33613 Rev. 7 - 4 11 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED

Ordering Information

Device Package Part Marking Status 7” Tape and Reel Quantity Part Number Suffix ZXSC100N8TA SO-8 ZXSC100 Obsolete 500/Tape & Reel TA ZXSC100X8TA MSOP-8 ZXSC100 Obsolete 1000/Tape & Reel TA Package Outline Dimensions (All Dimensions in mm) Please see http://www.diodes.com/package-outlines.html for the latest version. SO-8 b e E A 9° ( All sides) 4°±3° c Q h 45° R 0.1 D L Seating Plane Gauge Plane SO-8 Dim Min Max Typ A 1.40 1.50 1.45 A1 0.10 0.20 0.15 b 0.30 0.50 0.40 c 0.15 0.25 0.20 D 4.85 4.95 4.90 E 5.90 6.10 6.00 E1 3.80 3.90 3.85 E0 3.85 3.95 3.90 e -- -- 1.27 h - -- 0.35 L 0.62 0.82 0.72 Q 0.60 0.70 0.65 All Dimensions in mm ZXSC100 Document number: DS33613 Rev. 7 - 4 12 of 13 www.diodes.com October 2018 © Diodes Incorporated

ZXSC100X8 and ZXSC100N8 OBSOLETE – NO ALTERNATIVE ZXSC100 OBSOLETE – PART DISCONTINUED IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website, harmless against all damages. Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sal es channel. Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arisin g out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. Products described herein may be covered by one or more United States, international or foreign patents pending. Product nam es and markings noted herein may also be covered by one or more United States, international or foreign trademarks. This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the final and determinative format released by Diodes Incorporated. LIFE SUPPORT Diodes Incorporated produ cts are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein: A. Life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided i n the labeling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety -related requirements concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems- related information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes Incorporated products in such safety -critical, life support devices or systems. Copyright © 2018, Diodes Incorporated www.diodes.com ZXSC100 Document number: DS33613 Rev. 7 - 4 13 of 13 www.diodes.com October 2018 © Diodes Incorporated