Si9121 Vishay Siliconix High-Voltage, Non-Isolated Buck-Boost Converter for ISDN Digital Phones FEATURES D Fixed +5-V or +3.3-V Output D Integrated Floating Feedback Amplifier D On-Chip 70-V, 1.5-W N-Channel MOSFET Switch D Integrated High Voltage Start-Up Circuit, with VCC Regulator D D D D D −10-V to −60-V Input Voltage Range 95-kHz PWM Operation Integrated Soft-Start and Oscillator High Efficiency Over Full Load Range Under Voltage Lockout D Current Mode Control D Hiccup Mode Short Circuit Protection D Thermal Shutdown D SOIC-8 Narrow-Body Package DESCRIPTION The Si9121 simplifies the −48-V to +5-V or +3.3-V converter design for ISDN application by integrating the floating feedback error amplifier providing direct output voltage regulation. This approach eliminates the need for an external shunt regulator. The Si9121 also integrates a high voltage depletion mode MOSFET which allows the converter to be powered directly from the high input bus voltage without requiring an external start-up circuit. Combined with simple magnetic design due to its non-isolated topology, the Si9121 provides a one-chip solution for complete ISDN power supply. In order to reduce external component count, the Si9121 has a fully integrated 95-kHz oscillator and soft-start circuit. The Si9121 is available in both standard and lead (Pb)-free SOIC-8 pin packages, and is offered in either +5-V or +3.3-V fixed output options (Si9121DY-5 or Si9121DY-3, respectively). In order to satisfy the stringent ambient temperature requirements in many applications, the Si9121 is rated to the industrial temperature range of −40_C to 85_C. FUNCTIONAL BLOCK DIAGRAM GND VCC Regulator VCC Reference Generator VOUT BYPASS LX Control COMP VNEG VOUT +5 V/400 mA or +3.3 V/400 mA CS VNEG −48 V Document Number: 71112 S-40708—Rev. C, 19-Apr-04 www.vishay.com 1 Si9121 Vishay Siliconix ABSOLUTE MAXIMUM RATINGS (ALL VOLTAGES REFERENCED TO GND = 0 V) VNEG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −63 V VCS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VNEG −0.3 V to VCC + 0.3 V VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VNEG + 13.2 V ILX (peak current ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 A VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V Bypass, CS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VNEG −0.3 V to VCC +0.3 V (VLX − VCS ) internal power MOSFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 V Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −65 to 150_C Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150_C Power Dissipation (Package)a 8-Pin SOIC (Y Suffix)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25 W Thermal Impedance (QJA)a 8-Pin SOIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 _C/W Notes a. Device mounted with all leads soldered or welded to PC board. b. Derate 10 mW/_C above 25_C. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. RECOMMENDED OPERATING RANGE (ALL VOLTAGES REFERENCED TO GND = 0 V) VNEG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −10 V to −60 V VCC (externally supplied) . . . . . . . . . . . . . . . . VNEG + 9.5 V to VNEG + 12.0 V VCC (internally regulated) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VNEG + 8.5 V Digital Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V to VCC RECOMMENDED EXTERNAL COMPONENTS ( SEE TYPICAL APPLICATIONS CIRCUIT ) L = 68 mH, COUT = 220 mF // 0.1 mF, CIN = 33 mF, CBYPASS = 0.1 mF, CVCC = 1 mF, RSENSE = 0.25 W, 0.5 W SPECIFICATIONSa (All Voltages Are With Respect To VNEG Unless Otherwise Specified) Limits Test Conditions (Internally Regulated) Unless Otherwise Specified p Parameter Symbol VNEG = −10 to −60 V −40 to 85_C Tempb Minc Typd Maxc Full 4.80 5.00 5.20 Full 3.17 3.30 3.43 Unit Output Voltage (with respect to GND = 0 V) +5-V Converter +3.3-V Converter VOUT 10 mA <ILOAD < 250 mA V Line Regulation (with respect to GND = 0 V) Line Regulation −60 V v VNEG v −40 V Full 1 % V VCC (Internal Regulator) VCC Bias Voltage VCC Full 7.5 8.5 9.5 Full 6.6 7.6 8.7 UVLO Under Voltage Lockout Hysteresis VCC − VNEG Turn-On DV Room 0.6 Room 10 V Soft-Start Error Amplifier Start-Up Current ISS VOUT = 0 V mA Oscillator Switching Frequency fOSC Room 80 95 110 kHz Room 10 15 20 umho Error Amplifier Transconductance Clamp Voltage gm VCL Internal Error Amplifier Output Clamp Voltage Room 3.5 V Current Limit Threshold Voltage VCS Full rDS(on) Room 0.57 0.67 0.77 V 1.5 2.5 W MOSFET Switch N-Channel MOSFET www.vishay.com 2 Document Number: 71112 S-40708—Rev. C, 19-Apr-04 Si9121 Vishay Siliconix SPECIFICATIONSa (All Voltages Are With Respect To VNEG Unless Otherwise Specified) Limits Test Conditions (Internally Regulated) Unless Otherwise Specified p −40 to 85_C Symbol VNEG = −10 to −60 V Tempb IGND GND to VNEG Supply Current (External VCC Applied) ICC VOUT supply Current Parameter Minc Typd Maxc Full 1.2 1.5 VCC to VNEG +10 V; VNEG >−20 V Full 1.5 2.0 IOUT VOUT to VNEG Full 0.2 0.3 ISTART VCC = 0 V Full 5 30 Unit Supply Supply Current (Internally Regulater) Start-Up Current mA Thermal Shutdown Thermal Shutdown Temperature TOTP 170 Thermal Hysteresis THYS 25 _C Efficiency Efficiency 400 mA Output 400-mA Output, VNEG = −48 48 V +5 V Room 77 +3.3 V Room 73 % Notes a. Refer to PROCESS OPTION FLOWCHART for additional information. b. Room = 25_C, Full = as determined by the operating temperature suffix. c. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum. d. Typical values are for DESIGN AID ONLY, not guaranteed nor subject to production testing. DETAILED BLOCK DIAGRAM VOUT 4 5 10 mA R1* GND 6 R2* + − VCC − GM + 3.5 V + − H VREF 1.25 V 1.5 V − + L VNEG Soft Start Hiccup Discharge Mode OSC VCC COMP 2 mA OTP 7 8 0.6 V − + − Low Side Error Amp LX 50% Max. PWM Duty Cycle + R Q −VIN S BYPASS 3 OCL Bias/ Reference Circuit + 0.67 V − 1 − + − + 2 VNEG Document Number: 71112 S-40708—Rev. C, 19-Apr-04 8.5 V + − CS 0.6-V Hysteresis *R1 and R2 are internal voltage setting resistors used to set output voltage to fixed 3.3 V or 5 V. www.vishay.com 3 Si9121 Vishay Siliconix TYPICAL CHARACTERISTICS (INTERNALLY REGULATED, 25_C UNLESS NOTED) 5-V VOUT vs. Temperature 5.10 3.40 5.05 3.35 5.00 3.30 4.95 3.25 4.90 3.20 4.85 −40 −20 0 20 40 60 3.3-V VOUT vs. Temperature 3.45 V OUT (V) V OUT (V) 5.15 80 3.15 −40 100 −20 0 Temperature (_C) rDS(on) vs. Temperature 60 80 100 80 100 Frequency vs. Temperature 2.0 100 1.5 1.0 0.5 −40 40 105 Frequency (kHz) r DS(on) − On-Resistance ( W ) 2.5 20 Temperature (_C) 95 90 −20 0 20 40 60 80 85 −40 100 −20 0 Temperature (_C) 40 60 Supply Current vs. VNEG 1.4 Supply Current (I GND ) 20 Temperature (_C) 1.3 25_C 1.2 85_C −40_C 1.1 1.0 −60 −50 −40 −30 −20 −10 VNEG − (V) www.vishay.com 4 Document Number: 71112 S-40708—Rev. C, 19-Apr-04 Si9121 Vishay Siliconix TYPICAL CHARACTERISTICS (INTERNALLY REGULATED, 25_C UNLESS NOTED) Output Load vs. Efficiency (Si9121DY-3) No VCC Winding 90 90 80 VIN = 10 V 70 70 60 60 Efficiency (%) Efficiency (%) 80 VIN = 48 V 50 Output Load vs. Efficiency (Si9121DY-5) No VCC Winding VIN = 60 V 40 10 VIN 48 VIN 50 40 30 30 20 20 10 10 0 0 10 100 10 1000 100 IOUT (mA) Output Load vs. Efficiency (Si9121DY-5) With VCC Winding 90 VNEG = −10 V 80 1000 IOUT (mA) Output Load vs. Efficiency (Si9121DY-3) With VCC Winding 90 48 VIN 80 10 VIN 70 60 Efficiency (%) 70 Efficiency (%) 60 VIN VNEG = −48 V 50 40 VNEG = −60 V 60 VIN 60 50 40 30 30 20 20 10 10 0 0 10 100 IOUT (mA) Document Number: 71112 S-40708—Rev. C, 19-Apr-04 1000 10 100 1000 IOUT (mA) www.vishay.com 5 Si9121 Vishay Siliconix PIN CONFIGURATION AND ORDERING INFORMATION ORDERING INFORMATION SOIC-8 CS 1 VNEG 2 BYPASS COMP Part Number 8 LX 7 VCC 3 6 GND 4 5 VOUT Si9121 Temperature Range Package Si9121DY-5-T1 Si9121DY-5-T1—E3 Tape and Reel Si9121DY-3-T1 −40 40 to 85_C Si9121DY-3-T1—E3 Si9121DY-5 Top View Bulk Si9121DY-3 Eval Kit Temperature Range Board Type −10 10 to 70_C Surface Mount and Thru-Hole Si9121DB-5 Si9121DB-3 PIN DESCRIPTION Pin Number Name Function 1 CS 2 VNEG Current sense pin to detect the inductor current for current mode control and over current protection 3 BYPASS 4 COMP Compensation node to stabilize the converter 5 VOUT Output voltage feedback connected to the PWM summing comparator 6 GND Low impedance system ground 7 VCC Internally generated supply voltage for the internal circuit and MOSFET drive circuit. Decouple with an external bypass capacitor. 8 LX Negative supply voltage (−10 V to −60 V) +1.5-V bandgap reference. Decouple with 0.1 mF capacitor. Inductor connection node DETAILED DESCRIPTION Start-Up The UVLO circuit prevents the internal circuits from turning on if VCC is less than 7.6 V (typical) above the negative supply voltage at VNEG pin. With a typical hysteresis of 0.6 V, the controller is continuously powered on until the VCC voltage drops below 7.0 V. This hysteresis prevents the converter from oscillating during the start-up phase and unintentionally locking up the system. Once (VCC − VNEG) exceeds the UVLO threshold the internal reference, oscillator, and soft-start circuits are enabled. Soft-Start The Si9121 has an on-chip soft-start circuit which utilizes the error amplifier external compensation network to ramp the output NMOS transistor current limit which, in turn, allows the output voltage to rise gradually without excessive overshoot. The soft-start circuit is enable once the VCC voltage exceeds www.vishay.com 6 the UVLO threshold. For the recommended frequency compensation components (see Typical Application Circuit) the soft-start time is approximately 10 ms. Oscillator The oscillator is designed to operate at a nominal frequency of 95 kHz with no external components. The 95-kHz operating frequency allows the converter to operate in PWM mode during the full load condition even though the duty cycle is very low. The 95kHz switching frequency also allows the converter to operate at optimal efficiency without a large output inductor and capacitor. PWM Mode and Current Limit The Si9121 is a current-mode converter designed to operate in PWM mode. It features pulse-by-pulse peak current limiting such that when the peak current sensed voltage on the CS pin is greater than 0.67 V the switch is turned off for the remainder of the clock cycle. Document Number: 71112 S-40708—Rev. C, 19-Apr-04 Si9121 Vishay Siliconix DETAILED DESCRIPTION Bypass The bypass voltage of the Si9121 is set at a particular positive reference relative to the VNEG pin. The bypass voltage is used to set an accurate voltage and bias current for the on-chip oscillator and soft-start circuits. The 0.1-mF ceramic decoupling capacitor is recommended between the bypass and VNEG. No other components should be connected to this pin. dissipation the regulator’s thermal circuit will continue to pulse the regulator on and off. This is called thermal cycling. Hiccup Mode Short Circuit Protection In addition to the thermal shutdown and the cycle-by-cycle current limiting features already described, the Si9121 has a built-in hiccup mode timer to handle a continuous output short-circuit and to automatically restart the device when the short-circuit is removed. Error Amplifier With a −48-V bus voltage, the converter is referenced to the −48-V (VNEG) node as its system ground. However, the +5-V or +3.3-V output is referenced to the GND pin, which is normally connected to 0 V. To regulate this output voltage, the Si9121 has an on-chip error amplifier which continuously monitors the output voltage and compares it to a reference voltage. This difference signal is level-shifted to the low side circuit to control the power switch duty-cycle and hence the regulation of the output voltage. Frequency compensation for the error amplifier is achieved by connecting an external network between the COMP pin and the VNEG pin. VCC Regulator VCC is an internally generated bias supply voltage which should be externally bypassed with a 0.1-mF capacitor connected to the negative supply voltage, VNEG. No load current should be drawn from the VCC pin. VCC may be supplied from an external source of 9.5-V to 12-V referenced to VNEG. In this configuration, the internal VCC regulator is disabled when the VCC receives 9.5-V, or greater, above VNEG. Thermal Shutdown The Si9121 also includes thermal shutdown which shuts down the device when junction temperature exceeds 170_C due to over heating. In thermal shutdown once the die temperature cools to below 145_C the regulator is enabled. If the die temperature is excessive due to high package power Document Number: 71112 S-40708—Rev. C, 19-Apr-04 If an output short-circuit occurs, the device immediately enters a cycle-by-cycle current limiting mode. As long as the thermal shutdown is not activated then the Si9121 automatically determines whether the internal hiccup timer should be started by monitoring the COMP pin. If VCOMP exceeds an upper threshold voltage (approximately 3.5 V) the timer is started and the external network at the COMP pin is discharged by an internal 2-mA current sink until VCOMP reaches approximately 1.5 V. (Note: all voltages are with respect to VNEG). At this point, the circuit reverts to the normal soft-start mode, whereby the COMP network is charged by its internal soft-start 10-mA current source and the circuit will attempt to start up in the normal manner. However, if the output short circuit is still present, the converter will again enter the cycle-by-cycle current limiting mode until the COMP pin voltage reaches 3.5 V, whereupon this cycle repeats until the short circuit is removed. The duty cycle imposed by the hiccup timer allows the Si9121 to handle continuous short-circuit without damage as long as the recommended component values shown in the Typical Application Circuit are used. MOSFET Switch The low-side n-channel MOSFET switch is integrated to provide optimum performance and to minimize the overall converter size. The typical 1.5-W rDS(on) of the MOSFET allows the converter to deliver up to 2 W of output power. www.vishay.com 7 Si9121 Vishay Siliconix TYPICAL APPLICATION CIRCUIT GND L1 68 mH + 6 3 7 2 + 33 mF 80 V C4 0.1 mF C5* 0.1 mF C1 1 mF C6 GND BYPASS VCC LX VOUT COMP CS VNEG 220 mF C2 0.1 mF* C3 VOUT +5 V/400 mA or +3.3 V/400 mA 8 5 10MQ100N 4 1 R1 0.25 W 1/ W 2 Si9121DY-5 or Si9121DY-3 R2 75 kW (27 kW for Si9121DY-3) 180 pF C7 + 0.1 mF C8 VNEG −10 to −60 V *Optional FIGURE 1. Typical Applications Circuit Silk Screen T1 GND C1 33 mF 80 V 68 mH Np + C2* 0.1 mF 2 3 4 C3 0.1 mF Ns D2 BAS21 1 R1 0.25 1/ W 2 GND C4 180 pF C5 0.1 mF CS VNEG COIL VCC BYPASS GND COMP VOUT Si9121DY-5 8 7 C7 220 mF 10 V + C8* 0.1 mF D1 10MQ100N +VOUT +5 V @ 400 mA 6 5 C6 1 mF R2 75 kW (27 kW for Si9121DY-3) *Optional −VIN −10 to −60 V www.vishay.com 8 FIGURE 2. Si9121 Application with External Vcc Through Winding Document Number: 71112 S-40708—Rev. C, 19-Apr-04 Legal Disclaimer Notice Vishay Notice Specifications of the products displayed herein are subject to change without notice. Vishay Intertechnology, Inc., or anyone on its behalf, assumes no responsibility or liability for any errors or inaccuracies. Information contained herein is intended to provide a product description only. No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted by this document. Except as provided in Vishay's terms and conditions of sale for such products, Vishay assumes no liability whatsoever, and disclaims any express or implied warranty, relating to sale and/or use of Vishay products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright, or other intellectual property right. The products shown herein are not designed for use in medical, life-saving, or life-sustaining applications. Customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Vishay for any damages resulting from such improper use or sale. Document Number: 91000 Revision: 08-Apr-05 www.vishay.com 1