PT7750 Series 15 Amp 24V Input “Big Hammer III” Programmable ISR SLTS053A (Revised 6/30/2000) The PT7750 series is a +24V input, 15 Amp output, highperformance Integrated Switching Regulator (ISR) housed in a 27-pin SIP package. The 15A capability allows easy integration of the latest high-speed, low-voltage µPs and bus drivers into +24V distributed power systems. The PT7750 series has been designed to work in parallel with one or more of the PT7747 current boosters for increased Iout in increments of 15A. The output voltage of the PT7750 series can be easily programmed over a wide range with a 5-bit input. A differential remote sense is provided which automatically compensates for any voltage drop from the ISR to the load. 2000µF of output capacitance is required for proper operation. Pin-Out Information Standard Application PROGRAMMING PINS VID0 VID1 VID2 VID3 VID4 VIN REMOTE SENSE (+) 6 4 3 2 1 L1 1µH CIN + 26 PT7750 7 - 11 27 13 - 19 5 VOUT 20 - 25 12 COUT + LOAD SYNC OUT GND GND STBY* REMOTE SENSE (-) C in = Required 560µF electrolytic (See input filter note) Cout = Required 2000µF electrolytic L1 = Optional 1µH input choke Features Pin Function Pin Function 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 GND GND GND GND GND GND Vout Vout Vout Vout Vout Vout 27 Sync Out VID0 VID1 VID2 VID3 STBY* - Stand-by VID4 Vin Vin Vin Vin Vin Remote Sense Gnd GND For STBY* pin: open = output enabled ground = output disabled. • +24V bus input • High Efficiency • Differential Remote Sense • 27-pin SIP Package • Parallelable with PT7747 15A current boosters Remote Sense Vout Specifications PT7750 SERIES Characteristics (Ta = 25°C unless noted) Symbols Conditions Min Output Current Io Ta = +60°C, 200 LFM Ta = +25°C, natural convection 0.1 0.1 Input Voltage Range Vin 0.1A ≤ I o ≤ I o max Undervoltage Lockout Threshold Vuvl Output Voltage Tolerance ∆Vo Line Regulation Load Regulation Vo Ripple/Noise Transient Response with Cout = 2000µF Typ Max — — 15 (2) 15 (2) A 20.0 — 28.0 V 0.1A ≤ I o ≤ I o max — 18.7 — V Vin = +24V, Io = 15A PT7751 0°C ≤ Ta ≤ +55°C PT7756 — — — — ±80 ±160 mV Regline 20V ≤ Vin ≤ 28V, Io = Io max (w/remote sense) — ±15 — mV Regload Vin = +24V, 0.1 ≤ Io ≤ Io max (w/remote sense) — ±10 — mV Vn Vin = +24V, Io = Io max — 75 — mV ttr Vos Io step between 7.5A and 15A Vo over/undershoot — — 100 200 — — µSec mV — — — 88 84 80 — — — % (1) (1) Efficiency η Switching Frequency ƒo 20V ≤ V in ≤ 28V 0.1A ≤ I o ≤ 15A 300 350 400 Absolute Maximum Operating Temperature Range Ta — 0 — +85 Vin = +24V, Io = 10A Vo = 5.0V Vo = 3.3V Vo = 2.5V Units kHz (3) °C Storage Temperature Ts — -40 — +125 °C Weight — Vertical/Horizontal — 53/66 — grams Notes (1) ISR-will operate down to no load with reduced specifications. Please note that this product is not short-circuit protected. (2) The PT7750 series can be easily paralleled with one or more of the PT7747 Current Boosters to provide increased output current in increments of 15A (3) See safe operating area curves or contact the factory to determine the appropriate derating. Output Capacitors: The PT7750 series requires a minimum output capacitance of 2000µF for proper operation. Do not use Oscon type capacitors. The maximum allowable output capacitance is (42,000 ÷ Vout)µF for the PT7751, (96,000 ÷Vout)µF for the PT7756, or 15,000µF, whichever is less. Input Filter: An input inductor is optional for most applications. The input inductor must be sized to handle 9ADC with a typical value of 1µH. The input capacitance must be rated for a minimum of 8.0 Arms of ripple current when operated at maximum output current and maximum output voltage. Contact an applications engineer for input capacitor selection for applications at other output voltages and output currents. For technical support and more information, see inside back cover or visit www.ti.com/powertrends PT7750 Series 15 Amp 24V Input “Big Hammer III” Programmable ISR Programming Information Ordering Information PT7751 PT7751❏ ❏ = 2.5 to 5.6 Volts ❏ = 6.6 to 12.8 Volts PT7756❏ PT7756 VID4=1 VID4=0 VID4=1 VID4=0 VID3 VID2 VID1 VID0 Vout Vout Vout Vout 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 2.5V 2.6V 2.7V 2.8V 2.9V 3.0V 3.1V 3.2V 3.3V 3.4V 3.5V 3.6V 3.7V 3.8V 3.9V 4.0V 4.1V 4.2V 4.3V 4.4V 4.5V 4.6V 4.7V 4.8V 4.9V 5.0V 5.1V 5.2V 5.3V 5.4V 5.5V 5.6V 6.6V 6.8V 7.0V 7.2V 7.4V 7.6V 7.8V 8.0V 8.2V 8.4V 8.6V 8.8V 9.0V 9.2V 9.4V 9.6V (For dimensions and PC board layout, see Package Styles 1000 and 1010.) 9.8V 10.0V 10.2V 10.4V 10.6V 10.8V 11.0V 11.2V 11.4V 11.6V 11.8V 12.0V 12.2V 12.4V 12.6V 12.8V PT Series Suffix (PT1234X) Case/Pin Configuration Vertical Through-Hole N Horizontal Through-Hole A Horizontal Surface Mount C Logic 0 = Pin 12 potential (remote sense gnd) Logic 1 = Open circuit (no pull-up resistors) VID3 and VID4 may not be changed while the unit is operating. T Y P I C A L C H A R A C T E R I S T I C S PT7751 Safe Operating Area (@Vin=+24V, Over Vo Range) 90 90 80 Vout 80 12.0V 5.0V 70 3.3V 2.5V 60 50 Ambient Temperature (°C) Efficiency (%) Efficiency vs Output Current (@Vin=+24V) 100 40 70 Airflow Nat conv 60 60LFM 120LFM 50 200LFM 40 30 20 0 3 6 9 12 0 15 3 Output Current (A) 9 12 15 PT7756 Safe Operating Area (@Vin=+24V, Over Vo Range) Ouput Ripple vs Output Current (@Vin=+24V) 90 60 80 Vout 12.0V 40 5.0V 3.3V 30 2.5V 20 10 Ambient Temperature (°C) 70 50 Riplle (mV) 6 Output Current (A) 70 Airflow Nat conv 60 60LFM 120LFM 50 200LFM 40 30 20 0 0 3 6 9 12 0 15 Output Current (A) 3 6 9 12 15 Output Current (A) Power Dissipation vs Output Current (@Vin=+24V) 16 14 Pd (Watts) 12 Vout 10 12.0V 5.0V 8 3.3V 2.5V 6 4 2 0 0 3 6 9 12 15 Output Current (A) Note: SOA curves represent operating conditions at which internal components are at or below manufacturer’s maximum rated operating temperatures. For technical support and more information, see inside back cover or visit www.ti.com/powertrends Application Notes PT7750 Series Pin-Coded Output Voltage Adjustment on the “Big Hammer III” Series ISRs pins, low-level open drain MOSFET devices should be used over bipolar transistors. The inherent Vce(sat) in bipolar devices introduces errors in the device’s internal divider network. Discrete transistors such as the BSS138, 2N7002, IRLML2402, or the 74C906 hex open-drain buffer are examples of appropriate devices. Power Trends PT7750 series ISRs incorporating pincoded voltage control, use pins 1, 2, 3, 4, & 6 to adjust the ouput voltage. The control pins are identified VID0 - VID4 respectively. When the control pins are left open-circuit, the ISR output will regulate at its factory trimmed output voltage. Each control pin is internally connected to a precision resistor, and when grounded increases the output voltage by a set amount. The internal resistors are binary code weighted, allowing the output voltage of the ISR to be programmed as a function of a binary code. VID0 represents the LSB, and VID4 the MSB (or range change bit). The output voltage ranges offered by these regulators are compatible with some microprocessors, and provide a convenient method of output voltage selection for many other applications. Refer to Figure 1 below for the connection schematic, and the PT7750 Data Sheet for the programming code information. Active Voltage Programming: Special precautions should be taken when making changes to the voltage control progam code while the unit is powered. It is highly recommended that the ISR be either powered down or in standby. Changes made to the program code while Vout is enabled 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. If they are changed, the transients induced can overstress the device resulting in a permanent drop in efficiency. If the use of active devices prevents the program code being asserted prior to power-up, pull pin 5 (STBY) to the device GND during the period that the input voltage is applied to Vin. Releasing pin 5 will then allow the device output to execute a soft-start power-up to the programmed voltage. For more information on the use of the Standby function, consult the related application note, “Using the Standby Function on the ‘Big Hammer III’ Programmable ISR Series.” Notes: 1. The programming convention is as follows:Logic 0: Connect to pin12 (Remote Sense Ground). 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, always use pin 12 (Remote Sense Ground) as the logic “0” reference. While the regular ground (pins 13-19) can also be used for programming, doing so will degrade the load reglation of the product. 4. If active devices are used to ground the voltage control Figure 1 6 +24V 7-11 1µH (Optional) 4 3 2 1 VID4 - VID0 26 SNS(+) PT7750 Vin STBY 5 Synch Out 27 GND 13-19 Vo 20-25 SNS(-) 12 + Cin STBY COM For technical support and more information, see inside back cover or visit www.ti.com/powertrends + Cout L O A D Application Notes continued PT7750 Series Using the Standby Function on the PT7750 “Big Hammer III” Programmable ISRs Figure 1 For applications requiring output voltage On/Off control, the PT7750 “Big Hammer” ISRs incorporate a standby function1 . This feature may be used for power-up/shutdown sequencing, and to change the output voltage while input power is applied. See related notes: “Pin-coded Output Voltage Adjustment on the ‘Big Hammer III’ Series ISRs.” The standby function is provided by the STBY* control, pin 5. If pin 5 is left open-circuit the regulator operates normally, providing a regulated output whenever a valid supply voltage is applied to Vin (pins 7-11) with respect to GND (pins 13-19). Connecting pin 5 to ground 2 will set the regulator output to zero volts 3 . This places the regulator in standby mode, and reduces the input current to typically 30mA (50mA max). If a ground signal is applied to pin 5 prior to power-up, the regulator output will be held at zero volts during the period that input power is applied. The standby input must be controlled with an open-collector (or open-drain) discrete transistor (See Figure 1). Table 1 gives the threshold requirements. Table 1 Inhibit Control Threshold 2 Parameter Min Max Disable (VIL) –0.1V 6 4 3 2 1 26 VID4 - VID0 7-11 +24V SNS(+) 20-25 PT7750 Vin Synch STBY Out 27 5 V o =5.0V Vo GND SNS(-) 13-19 12 + L O A D + C in C out Q1 BSS138 Inhibit COM COM Turn-On Time: Turning Q1 in Figure 1 off, removes the lowvoltage signal at pin 5 and enables the output. Following a brief delay of 8-18ms, the output voltage of the PT7750 series regulators rise to full regulation within 20ms 4 . Figure 2 shows the typical output voltage waveform of a PT7751 following the prompt turn-off of Q1 at time t =0 secs. The output voltage in Figure 1 is set to 5.0V by connecting VID0 (pin 1), VID3 (pin 4), and VID4 (pin 6) to the Remote Sense Gnd (pin 12)*. The waveform in Figure 2 was measured with a 24V input source voltage, and 10A resistive load. 0.3V Figure 2 Notes: 1. The Standby/Inhibit control logic is similar for all Power Trends’ modules, but the flexibility and threshold tolerances will be different. For specific information on this function for other regulator models, consult the applicable application note. 2. The Standby input on the PT7750 regulator series must be controlled using an open-collector (or open-drain) discrete transistor. Do Not use a pull-up resistor. The control input has an open-circuit voltage of about 1.5Vdc. To set the regulator output to zero, the control pin must be “pulled” to less than 0.3Vdc with a low-level 0.1mA sink to ground. 3. When placed in the standby mode, the regulator output discharges the output capacitance with a low impedance to ground. If an external voltage is applied to the output, it will sink current and possibly over-stress the part. 4. The turn-off time of Q1, or rise time of the standby input is not critical on the PT7750 series. Turning Q1 off slowly, over periods up to 100ms, will not affect regulator operation. However, a slow turn-off time will increase both the initial delay and rise-time of the output voltage. Vin (2V/Div) 0 5 10 15 20 25 t (milli - secs) * Consult the data sheet for details on other VID codes. For technical support and more information, see inside back cover or visit www.ti.com/powertrends I MPORTANT NOTI CE Te xas Instrume nts and its subsidiarie s (TI) re se rve the right to make change s to the ir products or to discontinue any product or se rvice without notice , and advise custome rs to obtain the late st ve rsion of re le vant information to ve rify, be fore placing orde rs, that information be ing re lie d on is curre nt and comple te . All products are sold subje ct to the te rms and conditions of sale supplie d at the time of orde r acknowle dgme nt, including those pe rtaining to warranty, pate nt infringe me nt, and limitation of liability. TI warrants pe rformance of its se miconductor products to the spe cifications applicable at the time of sale in accordance with TI’s standard warranty. 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