PT8120 Series 30-A 12-V Input Programmable Integrated Switching Regulator SLTS158B (Revised 6/6/2002) Features • • • • Single Device: 30ADC +12V-Input High Efficiency: 92% @3.3V Programmable Output: (VRM Compatible 5-bit Codes) • Multiphase Topology • Output Remote Sense • Over-Current Protection Description • • • • Thermal Shutdown Standby On/Off Control Space-Saving Package Solderable Copper Case Ordering Information The PT8120 Excalibur™ power modules are a family of high-output, high-efficiency, fully integrated switching regulators (ISRs), housed in a solderable 31-pin space-saving copper package. These modules operate from a nominal input voltage of +12V to provide up to 30A of output current at output voltages as low as 0.8V. The output voltage is programmable via a 5-bit input code. The PT8120 family incorporates a state-of-the-art, 2-phase, multiple power path topology. This extends the output current range while providing superior transient response and input current ripple performance. The PT8120 family is designed to power high-end computing and signal processing applications, all of which demand high output currents at low supply voltages. The modules have a number of features to facilitate system integration. These include over-current protection, thermal shutdown, an on/off standby control, and an output remote sense to compensate for voltage drop between the regulator and the load. In addition, the voltage programming codes for the PT8121, PT8122, & PT8124 are compatible with Intel’s® VRM specifications. PT8121H PT8122H PT8123H PT8124H PT8125H = = = = = 1.3V 1.075V 0.8V 1.05V 4.5V to 3.5V to 1.85V to 1.575V to 1.825V to 7.6V PT Series Suffix (PT1234 x ) Case/Pin Configuration Vertical Horizontal SMD Order Suffix N A C Package Code (EKH) (EKF) (EKG) (Reference the applicable package code drawing for the dimensions and PC board layout) PT812x Standard Application (See page 4 for PT8124 application schematic) PROGRAMMING PINS VID0 VID1 VID2 VID3 VID4 REMOTE SENSE VID Common 11 Lin VIN 12–16 5 4 3 2 1 PT8120 Series 31 VOUT 23–30 (Except PT8124) 1µH + CIN 6 17–22 GND STBY* For technical support and more information, see inside back cover or visit www.ti.com L O A D + COUT GND Cin = Required 1500µF electrolytic Cout = Required 660µF low ESR OS-Con®, or 1,200µF aluminum electrolytic L in = Optional 1µH input choke PT8120 Series 30-A 12-V Input Programmable Integrated Switching Regulator Pin-Out Information (Except PT8124 †) Pin Function Pin Function Pin Function 1 VID 0 12 Vin 22 GND 2 VID 1 13 Vin 23 Vout 3 VID 2 14 Vin 24 Vout 4 VID 3 15 Vin 25 Vout 5 VID 4 16 Vin 26 Vout 6 STBY * 17 GND 27 Vout 7 Do Not Connect 18 GND 28 Vout 8 Do Not Connect 19 GND 29 Vout 9 Do Not Connect 20 GND 30 Vout 10 Do Not Connect 21 GND 31 Remote Sense 11 VID Common * For STBY pin: Open =Output Enabled Ground =Output Disabled † See page 4 for PT8124 pin-out Output Voltage Programming Information (Except PT8124) PT8122 (VRM 9.0) PT8121 (VRM 8.3/8.4) VID 3 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 VID 2 VID 1 VID 0 1 1 1 1 1 0 1 0 1 1 0 0 0 1 1 0 1 0 0 0 1 0 0 0 1 1 1 1 1 0 1 0 1 1 0 0 0 1 1 0 1 0 0 0 1 0 0 0 VID 4=1 Vout 2.00V 2.10V 2.20V 2.30V 2.40V 2.50V 2.60V 2.70V 2.80V 2.90V 3.00V 3.10V 3.20V 3.30V 3.40V 3.50V VID 4=0 Vout 1.30V 1.35V 1.40V 1.45V 1.50V 1.55V 1.60V 1.65V 1.70V 1.75V 1.80V 1.85V 1.90V 1.95V 2.00V 2.05V VID 4=1 Vout 1.075V 1.100V 1.125V 1.150V 1.175V 1.200V 1.225V 1.250V 1.275V 1.300V 1.325V 1.350V 1.375V 1.400V 1.425V 1.450V VID 4=0 Vout 1.475V 1.500V 1.525V 1.550V 1.575V 1.600V 1.625V 1.650V 1.675V 1.700V 1.725V 1.750V 1.775V 1.800V 1.825V 1.850V PT8123 (Custom Code) VID 4=1 Vout 0.800V 0.825V 0.850V 0.875V 0.900V 0.925V 0.950V 0.975V 1.000V 1.025V 1.050V 1.075V 1.100V 1.125V 1.150V 1.175V VID 4=0 Vout 1.200V 1.225V 1.250V 1.275V 1.300V 1.325V 1.350V 1.375V 1.400V 1.425V 1.450V 1.475V 1.500V 1.525V 1.550V 1.575V PT8125 (Custom Code) VID 4=1 Vout 4.5V 4.6V 4.7V 4.8V 4.9V 5.0V 5.1V 5.2V 5.3V 5.4V 5.5V 5.6V 5.7V 5.8V 5.9V 6.0V VID 4=0 Vout 6.1V 6.2V 6.3V 6.4V 6.5V 6.6V 6.7V 6.8V 6.9V 7.0V 7.1V 7.2V 7.3V 7.4V 7.5V 7.6V Notes: i) Logic 0 = Connect to VID Common ii) Logic 1 = Open circuit (no pull-up resistors) iii) VID3 and VID4 may not be changed while the unit is operating. iv) See page 4 for PT8124 (VRM 8.5) programming information. For technical support and more information, see inside back cover or visit www.ti.com PT8120 Series 30-A 12-V Input Programmable Integrated Switching Regulator PT8121 /2 /3 /5 Specifications (Unless otherwise stated T a =25°C, C in =1,500µF, Cout =660µF, V in =12V, & Io = Iomax ) PT8121 /2 /3 /5 Only Characteristics Symbols Output Current Io Conditions Natural convection or 60°C with 200LFM airflow Min Vo ≤3.5V Vo ≥4.5V 0.1 0.1 (1) (1) Typ Max Units — — 30 28 A V Input Voltage Range Vin Over Io Range 10.8 — 13.2 Set-Point Voltage Tolerance Vo tol Over Vo range — ±1 ±2 %V Line Regulation ∆Reg line Over Vin range — ±10 — mV Load Regulation ∆Regload Over Io range — ±10 — mV Temperature Variation ∆Reg temp –40°C ≤T a ≤85°C — ±0.5 — %Vo Total Output Voltage Variation ∆Votot Includes set-point, line load, –40°C ≤Ta ≤ 85°C — — ±3 %V Efficiency η Io =15A Vo =5.0V Vo =3.3V Vo =2.5V Vo =1.8V Vo =1.5V Vo =1.2V — — — — — — 94 92 90 86 84 81 — — — — — — % =5.0V =3.3V =2.5V =1.8V =1.5V =1.2V — — — — — — 93 91 88 84 82 78 — — — — — — % mV Io =I omax Vo Vo Vo Vo Vo Vo Vo Ripple (pk-pk) Vr 20MHz bandwidth — 20 — Transient Response ttr 1A/µs load step, 50% to 100% Iomax — 50 — µSec ∆Vtr Vo over/undershoot — 100 — mV Over-Current Threshold I TRIP Reset followed by auto-recovery — — 40 45 — — A Switching Frequency ƒs Over load range 300 350 400 kHz — — 0.5 Open (2) 0.8 — 35 — mA — 30,000 µF — — µF — +85 (5) °C Vo ≥4.5V Vo ≤3.5V Standby Control (pin 6) Input High Voltage Input Low Voltage Input Low Current Referenced to GND (pins 17–22) VIH VIL I IL Pin 6 to GND — -0.2 — Standby Input Current Iin standby Pin 6 to GND — External Output Capacitance Cout See PT812x application schematic 660 External Input Capacitance C in See PT812x application schematic 1,500 Operating Temperature Range Ta Over Vin Range –40 Storage Temperature Ts — -40 — +125 °C Mechanical Shock Per Mil-STD-883D, Method 2002.3 1 msec, Half Sine, mounted to a fixture — 500 — G’s Mechanical Vibration Mil-STD-883D, Method 2007.2 20-2000 Hz, soldered in PCB — 20 (6) — G’s — 55 — grams Weight — Vertical/Horizontal Flammability — Materials meet UL 94V-0 (3) (4) V mA Notes: (1) ISR-will operate down to no load with reduced specifications. (2) The Standby input (pin 6) has an internal pull-up. If it is left open-circuit the PT812x will operate when input power is applied. A low-leakage MOSFET is recommended to control this input. The open-circuit voltage is nominally 5V. See application notes for interface considerations. (3) The PT8120 regulators require a minimum of 660µF, low ESR ouput capacitance (1,200µF for standard aluminum electrolytic) for proper operation. (4) For operation below 0°C, Cout must have stable characteristics. Use either low ESR tantalum or Oscon® capacitors. (5) See safe Operating Area curves or consult factory for the appropriate derating. (6) The case pins on the through-hole package types (suffixes N & A) must be soldered. For more information see the applicable package outline drawing. Input Filter: An input filter inductor is optional for most applications. The inductor must be rated to handle the projected input current. A rating of 10ADC for Vout ≤3.3V, and 15ADC for V out ≥4.5V is recommended. The input capacitance must be rated for a minimum of 1.6Arms of ripple current. For transient or dynamic load applications, additional capacitance may be required. For more information consult the application note on capacitor selection. For technical support and more information, see inside back cover or visit www.ti.com PT8120 Series 30-A 12-V Input Programmable Integrated Switching Regulator PT8124 Voltage Programming Information PT8124 Pin-Out Information (VRM 8.5) Pin Function Pin Function 1 VID 25mV 17 GND 2 VID 0 18 GND 3 VID 1 19 GND 4 VID 2 20 GND 5 VID 3 21 GND 6 STBY 22 GND 7 Do Not Connect 23 Vout 8 Do Not Connect 24 Vout 9 Do Not Connect 25 Vout 10 Do Not Connect 26 Vout 11 VID Common 27 Vout 12 Vin 28 Vout 13 Vin 29 Vout 14 Vin 30 Vout 15 Vin 31 Remote Sense 16 Vin VID 3 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 * For STBY pin: Open =Output Enabled Ground =Output Disabled VID 2 VID 1 VID 0 1 1 1 1 1 0 1 0 1 1 0 0 0 1 1 0 1 0 0 0 1 0 0 0 1 1 1 1 1 0 1 0 1 1 0 0 0 1 1 0 1 0 0 0 1 0 0 0 VID 25mV=0 Vout 1.300V 1.350V 1.400V 1.450V 1.500V 1.550V 1.600V 1.650V 1.700V 1.750V 1.800V 1.050V 1.100V 1.150V 1.200V 1.250V VID 25mV=1 Vout 1.325V 1.375V 1.425V 1.475V 1.525V 1.575V 1.625V 1.675V 1.725V 1.775V 1.825V 1.075V 1.125V 1.175V 1.225V 1.275V Notes: i) Logic 0 = Connect to VID Common ii) Logic 1 = Open circuit (no pull-up resistors) iii) VID2 and VID3 may not be changed while the unit is operating. PT8124 Standard Application PROGRAMMING PINS VID 25mV VID 0 VID 1 VID 2 VID 3 REMOTE SENSE VID Common 11 Lin VIN 3 2 1 31 VOUT 23–30 (Only) 1µH + STBY* 4 PT8124 12–16 CIN GND 5 6 17–22 L O A D + COUT GND Cin = Required 1500µF electrolytic Cout = Required 660µF low ESR OS-Con®, or 1,200µF aluminum electrolytic L in = Optional 1µH input choke For technical support and more information, see inside back cover or visit www.ti.com PT8120 Series 30-A 12-V Input Programmable Integrated Switching Regulator PT8124 Specifications (Unless otherwise stated T a =25°C, Cin =1,500µF, C out =660µF, Vin =12V, & I o = I omax ) PT8124 Only Characteristics Symbols Conditions Min Output Current Io Natural convection or 60°C with 200LFM airflow Typ Max Units 0.1 — 30 A Input Voltage Range Vin Over Io Range Set-Point Voltage Tolerance Vo tol Over Vo range, I o =0.5A 10.8 — 13.2 V — ±1 ±2 Line Regulation ∆Reg line Over Vin range %V — ±10 — mV Load Regulation (Droop) ∆Regload Over Io range — 2 — mV/A Temperature Variation ∆Reg temp –40°C ≤Ta ≤85°C, , Io =0.5A — ±0.5 — %Vo Total Output Voltage Variation ∆Votot Includes set-point, line, load –40°C ≤Ta ≤ 85°C — — 85 (2) mV Efficiency η Io =15A Vo =1.8V Vo =1.5V Vo =1.2V — — — 86 84 81 — — — % Io =I omax Vo =1.8V Vo =1.5V Vo =1.2V — — — 84 82 78 — — — % mV (1) Vo Ripple (pk-pk) Vr 20MHz bandwidth — 20 — Transient Response ttr 1A/µs load step, 50% to 100% Iomax — 50 — µSec ∆Vtr Vo over/undershoot — 50 — mV Over-Current Threshold I TRIP Reset followed by auto-recovery — 47 — A Switching Frequency ƒs Over load range 300 350 400 kHz Standby Control (pin 6) Input High Voltage Input Low Voltage Input Low Current VIH VIL I IL Pin 6 to GND — -0.2 — — — 0.5 Open (3) 0.8 — Standby Input Current Iin standby Pin 6 to GND — 35 — mA External Output Capacitance Cout See PT8124 application schematic 660 — 30,000 µF External Input Capacitance C in See PT8124 application schematic 1,500 — — µF Operating Temperature Range Ta Over Vin Range –40 — +85 (6) °C Storage Temperature Ts — -40 — +125 °C Mechanical Shock Per Mil-STD-883D, Method 2002.3 1 msec, Half Sine, mounted to a fixture — 500 — G’s Mechanical Vibration Mil-STD-883D, Method 2007.2 20-2000 Hz, soldered in PCB — 20 (7) — G’s — 55 — grams Referenced to GND (pins 17–22) Weight — Vertical/Horizontal Flammability — Materials meet UL 94V-0 (4) (5) V mA Notes: (1) ISR-will operate down to no load with reduced specifications. (2) Total output voltage variation includes load regulation droop, which is required for compliance with specification VRM 8.5-4 (3) The Standby input (pin 6) has an internal pull-up. If it is left open-circuit the PT812x will operate when input power is applied. A low-leakage MOSFET is recommended to control this input. The open-circuit voltage is nominally 5V. See application notes for interface considerations. (4) The PT8120 regulators require a minimum of 660µF, low ESR ouput capacitance (1,200µF for standard aluminum electrolytic) for proper operation. (5) For operation below 0°C, Cout must have stable characteristics. Use either low ESR tantalum or Oscon® capacitors. (6) See safe Operating Area curves or consult factory for the appropriate derating. (7) The case pins on the through-hole package types (suffixes N & A) must be soldered. For more information see the applicable package outline drawing. Input Filter: An input filter inductor is optional for most applications. The inductor must be rated to handle the projected input current. A rating of 10ADC for Vout ≤3.3V, and 15ADC for V out ≥4.5V is recommended. The input capacitance must be rated for a minimum of 1.6Arms of ripple current. For transient or dynamic load applications, additional capacitance may be required. For more information consult the application note on capacitor selection. For technical support and more information, see inside back cover or visit www.ti.com PT8120 Series 30-A 12-V Input Programmable Integrated Switching Regulator Characteristic Data; Vin =12V Safe Operating Area; Vin =12V (See Note A) Efficiency vs Output Current PT8120 Series, Vout =5V 90 100 VOUT 80 Ambient Temperature (°C) 90 Efficiency - % (See Note B) 5V 3.3V 2.5V 1.8V 1.5V 1.2V 1.0V 0.8V 80 70 Airflow 70 400LFM 200LFM 120LFM 60LFM Nat conv 60 50 40 30 60 20 0 6 12 18 24 0 30 6 12 Iout (A) Output Ripple vs Output Current 24 30 PT8120 Series, Vout =3.3V 90 25 80 VOUT 5V 0.8V 3.3V 1.5V 15 10 Ambient Temperature (°C) 30 20 Ripple - mV 18 Iout (A) 5 Airflow 70 Nat conv 60LFM 120LFM 200LFM 400LFM 60 50 40 30 0 20 0 6 12 18 24 0 30 6 12 Iout (A) 18 24 30 Iout (A) Power Dissipation vs Output Current PT8120 Series, Vout =1.5V 15 90 Pd - Watts VOUT 5V 3.3V 1.5V 0.8V 9 6 3 Ambient Temperature (°C) 80 12 Airflow 70 400LFM 200LFM 120LFM 60LFM Nat conv 60 50 40 30 0 20 0 6 12 18 Iout (A) 24 30 0 6 12 18 24 30 Iout (A) Note A: Characteristic data has been developed from actual products tested at 25°C. This data is considered typical data for the Converter. Note B: SOA curves represent the conditions at which internal components are at or below the manufacturer’s maximum operating temperatures For technical support and more information, see inside back cover or visit www.ti.com Application Notes PT8120 Series & PT8139 Capacitor Recommendations for the PT8120 Series of Programmable ISRs Input Capacitors The recommended input capacitor(s) is determined by 1.6 Arms minimum ripple current rating and 1,500µF minimum capacitance. Ripple current and Equivalent Series Resistance (ESR) values are the major considerations along with temperature when selecting the proper capacitor. The tantalum capacitors listed below cannot be used on the input bus since they are not rated for 12V operation. Output Capacitors The minimum required output capacitance is 660µF (organic/polymer), or 1,200 (aluminum electrolytic) with a maximum ESR less than or equal to 50mΩ. Failure to observe this requirement may lead to regulator instability or oscillation. Electrolytic capacitors have poor ripple performance at frequencies greater than 400kHz, but excellent low frequency transient response. Above the ripple frequency ceramic decoupling capacitors are necessary to improve the transient response and reduce any microprocessor high frequency noise components apparent during higher current excursions. Preferred low ESR type capacitor part numbers are identified in the Table 1 below. Tantalum Characteristics Tantalum capacitors are recommended on the output bus but only AVX TPS Series, Sprague 593D/594/595 Series, or Kemet T495/T510,520 Series. These capacitors are recommended over other types due to their higher surge current, excellent power dissipation and ripple current ratings. As a caution, the TAJ Series by AVX is not recommended. This series exhibits considerably higher ESR, reduced power dissipation and lower ripple current capability. The TAJ Series is also less reliable compared to the TPS series when determining power dissipation capability. Capacitor Table Table 1 identifies the characteristics of capacitors from a number of vendors with acceptable ESR and ripple current (rms) ratings. The suggested minimum quantities per regulator for both the input and output buses are identified. This is not an extensive capacitor list. Capacitors from other vendors are available with comparable specifications. Those listed are for guidance. The RMS ripple current rating and ESR (Equivalent Series Resistance at 100kHz) are the critical parameters are necessary to insure both optimum regulator performance and long capacitor life. Table 1 Capacitors Characteristic Data Capacitor Vendor/ Series Capacitor Characteristics Quantity Working Voltage Value(µF) (ESR) Equivalent Series Resistance 105°C Maximum Ripple Current(Irms) Physical Size(mm) Input Bus Output Bus Vendor Part Number Panasonic FC (Radial) 35V 25V 1500 1500 0.028Ω 0.029Ω 2490mA 2205mA 18× 20 16× 20 1 1 1 1 EEUFC1V152S EEUFC1E152S FC/FK (Surface Mount) 16V 25V 16V 4700 2200 2200 0.033Ω 0.028Ω 0.038Ω 2060mA 2490mA 2000mA 18×16.5 18×21.5 18×16.5 1 1 2 1 1 1 EEVFK1C472M EEVFC1E222N EEVFC1C222N United Chemi-con LXZ Series 35V 25V 16V 1800 1800 2700 0.028Ω 0.029Ω 0.029Ω 2490mA 2210mA 2210mA 18× 20 16×20 16× 20 1 1 1 1 1 1 LXZ35VB182M18X20LL LXZ25VB182M16X20LL LXZ16VB272M16X20LL Nichicon PW Series 25V 25V 1000 1800 0.038÷2Ω 0.029Ω 3200mA 2205mA 12.5x20 16x20 2 1 1 1 UPW1E102MHH UPW1E182MHH6 PM Series 25V 1500 0.034Ω 1770mA 16×20 1 1 UPM1E152MHH6 Os-con:( Organic) SS SV (Surface Mount) 10V 10V 330 330 0.025Ω 0.020Ω 3500mA 3800mA 10×10.5 10.3×10.3 N/R(1) N/R(1) 2 2 10SS330M (Vo<6V) 10SV330 (Vo<6V) AVX Tantalum TPS (Surface Mount) 10V 10V 330 330 0.1Ω÷2 =0.05Ω 0.06Ω÷2 =0.03Ω >2500mA >3000mA 7.3L ×5.7W ×4.1H N/R(1) N/R(1) 2 2 TPSE337M010R0100 (Vo<5V) TPSV337M010R0060( Vo<5V) Kemet Polymer/Tantalum T520Series (Surface Mount) 10V 10V 330 330 0.040÷2Ω 0.040÷2Ω 1800mA >1800mA 4.3W ×7.3L ×4.0H N/R(1) N/R(1) 2 2 T520X337M010AS (Vo<6V) T520D330M006AS (Vo<4V) Sprague Tantalum 594D Series (Surface Mount) 10V 330 0.045÷2Ω 2360mA 7.2L ×6W ×4.1H N/R(1) 2 594D337X0010R2T(Vo<5V) Note: (N/R -Not recommended) The 10V-rated tantalum capacitors cannot be used on the input bus. For technical support and more information, see inside back cover or visit www.ti.com Application Notes PT8120 Series & PT8139 Using the On/Off Standby Function of the PT8120 Series of Programmable ISRs The PT8120 series of programmable ISRs incorporates an On/Off Standby function. This feature may be used to turn the regulated output of the module off while input voltage is applied. This places the module in “standby” mode. The standby control may be used for power-up sequencing, or wherever there is a requirement to control the module’s output status from another circuit. 2. In the standby mode the output of the regulator is tristate, and the output voltage falls at the rate that the load circuit discharges the output filter capacitors. 3. When the ground signal to the Standby pin is removed, the regulator output initiates a soft-start cycle by first asserting a low impedance to ground. If an external voltage is applied to the output bus, it will sink current and possibly over-stress the part. The Standby function is provided by the STBY* control, pin 6. If pin 6 is left open-circuit the regulator operates normally, providing a regulated output when a valid supply voltage is applied to Vin (pins 10-16) with respect to GND (pins 17-22). Connecting pin 6 to ground 1 places the regulator in standby mode 2, and reduces the input current to typically 35mA. Applying a ground signal to pin 6 prior to power-up, will inhibit the output during the period that input power is applied. When the ground signal to pin 6 is removed, the regulator initiates a softstart to re-establish the set output voltage. 3 To ensure that the regulator output is properly enabled, the STBY* control pin must be open circuit. Table 1 Standby Control Requirements 2 Parameter Min Typ V IH — V IL –0.2V Turn-On Time Turning Q 1 in Figure 1 off, removes the low-voltage signal at pin 6. After approximately 5-ms the regulator output rises and reaches full regulation within 40ms. Fig. 2 shows the typical waveforms of a PT8121 following the prompt turn-off of Q1. The turn-off of Q1 corresponds to the rise in Vstby. The output voltage was set to 3.3V, and the waveforms were measured with a 12V input source, and 18A resistive load. Figure 2 Max Open Cct. 1 — I STBY 0.8V –0.5mA Vo (1V/Div) Notes: 1. The standby on a PT8120 series regulators must be controlled with an open-collector (or open-drain) transistor (See fig. 1). Do Not use a pull-up resistor. Table 1 gives the STBY* pin parameters. The control pin has an open-circuit voltage of 5Vdc. To shut the regulator output off, the control pin must be “pulled” to less than 0.8Vdc with a low-impedance sink to ground. Iin (5A/Div) Vstby (5V/Div) HORIZ SCALE: 5ms/Div Figure 1 VO SENSE 11 VIN VID Common Lin 12–16 1µH CIN STBY 6 1 =Off GND Q1 BSS138 4 3 2 VID4 – VID0 PT8121 V IN + 5 1 31 Sense VOUT VO =3.3V 23–30 GND 17–22 L O A D + COUT GND For technical support and more information, see inside back cover or visit www.ti.com Application Notes PT8120 Series & PT8139 Pin-Coded Output Voltage Programming of the 30-A Rated PT8120 Series Regulators 4. If active devices are used to ground the voltage control pins, low-level open drain MOSFETs should be used over bipolar transistors. The inherent Vce(sat) in bipolar devices introduces errors in the device’s internal voltage control circuit. Discrete transistors such as the BSS138, 2N7002, IRLML2402, are examples of appropriate devices. The PT8120 series of Excalibur® ISRs incorporate a pin-coded output voltage control. These regulators must be programmed to a specific output voltage from a preset range defined by the regulator model. Programming is achieved by selectively connecting the control inputs, “VID0–VID4” (pins 1–5), to the “VID Common” (pin 11). 1 The programming code and voltage range for each model is defined in the data sheet. Refer to the PT8120 Series data sheet for more information. The program codes for the PT8121, PT8122, and PT8124 models are also compatible with some of the “Voltage ID” codes defined by Intel’s® VRM specifications. Figure 1 shows the pin-strap connections for selecting the desired output voltage from the program code range. Active Voltage Programming: Special precautions should be taken when making changes to the voltage control progam code while the output is active. It is recommended that the ISR be powered down or held placed in standby. Changes made to the program code while Vout is active induces high current transients through the device. This is the result of the electrolytic output capacitors being either charged or discharged to the new output voltage set-point. The transient current can be minimized by making only incremental changes to the binary code, i.e. one LSB at a time. A minimum of 100µs settling time between each program state is also recommended. Making non-incremental changes to VID3 and VID4 with the output enabled is discouraged. The transients induced may activate the module’s over-current protection. If the program code cannot be asserted prior to power-up, pull pin 6, STBY*, to GND during the period that the input voltage is applied. The release of pin 6 will then to allow the device to initiate a soft-start power-up to the program voltage. Notes: 1. The programming convention is as follows:Logic 0: Connect to pin 11 (VID Common). Logic 1: Open circuit/open drain (See notes 2, & 4) 2. Do not connect pull-up resistors to the voltage programming pins. 3. To minimize output voltage error, use pin 11 (VID Common) as the logic “0” reference. If the regulator is used to power a VRM compatible microprocessor this may not be practical. In this case connect pin 11 to pins 17–22, or the ground plane close to the regulator. Figure 1 VID0 VID1 VID2 VID3 VO SENSE VID4 11 VIN 5 Lin 12–16 1µH 3 2 1 6 31 Sense PT8121 VIN STBY + 4 VID4 – VID0 VID Common VOUT VO =2.5V 23–30 GND 17–22 CIN GND For technical support and more information, see inside back cover or visit www.ti.com L O A D + COUT GND IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. 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