PT3400 Series 35-W 48-V Input Isolated DC/DC Converter SLTS164B - JULY 2002 - REVISED OCTOBER 2002 Features • Input Voltage Range: 36V to 75V • 35W Output Power • 90% Efficiency • 1500 VDC Isolation • Low Profile (8 mm) • Adjustable Output Voltage • Dual-Logic On/Off Enable • Power-Up Sequence Control Description Ordering Information The PT3400 Excalibur™ power modules are a series of 35-W rated DC/DC converters housed in a low-profile space-saving copper case. Fully isolated for telecom applications, the series includes a number of standard voltages, including 1.0 VDC. Other applications include industrial, high-end computing, and other distributed power applications that require input-to-output isolation. PT3400 modules incorporate a feature that simplifies the design of multiple voltage power supplies in DSP and ASIC applications. Using the SEQ control pin, the output voltage of two PT3400 modules in a power supply system can be made to self sequence at powerup. Other features include output voltage adjust, over-current protection, input undervoltage lockout, and a differential remote sense to compensate for any voltage drop between the converter and load. PT3401H PT3402H PT3403H PT3404H PT3405H PT3406H PT3407H PT3408H = 3.3V/10A = 2.5V/12A = 1.8V/12A = 1.5V/16A = 1.4V/16A = 1.2V/16A = 1V/16A = 5V/7A • • • • • Pin-Out Information (33W) (30W) (21.6W) (24W) (22.4W) (19.2W) (16W) (35W) Pin PT Series Suffix (PT1234x ) Case/Pin Configuration Order Suffix Package Code N A C Vertical Horizontal SMD Differential Remote Sense Over-Current Protection Space Saving Package Solderable Copper Case Safety Approvals Pending Function 1 EN 1 2 EN 2* 3 –Vin 4 +Vin 5 SEQ 6 Vout Adj 7 –V sense 8 –Vout 9 –Vout 10 –Vout 11 +Vout (EPL) (EPM) (EPN) 12 +Vout 13 +Vout (Reference the applicable package code drawing for the dimensions and PC board layout) 14 +V sense * Negative logic Shaded functions indicate those pins that are referenced to –Vin . Standard Application 4 +V SENSE +V OUT 1 2 EN 1 3 Remote Sense (+) † C OUT 330µF EN 2 –V IN –V SENSE SEQ V o Adj 5 6 +VOUT 11–13 PT3400 –V OUT –VIN 14 +V IN –VOUT 8–10 7 L O A D + +VIN * Remote Sense (–) VO Adj SEQ For technical support and more information, see inside back cover or visit www.ti.com † An output capacitor is required on models with an output voltage less than 2.5V. * –Vsense (pin 7) must be connected to -Vout , either at the load or directly to pin 8 of the converter. PT3400 Series 35-W 48-V Input Isolated DC/DC Converter Specifications SLTS164B - JULY 2002 - REVISED OCTOBER 2002 (Unless otherwise stated, T a =25°C, V in =48V, Cin =0µF, Io =I omax, and Cout as required) Characteristic Symbol Conditions Output Current Io Over Vin range Min Vo ≤ 1.5V Vo = 1.8V/2.5V Vo = 3.3V Vo = 5V Input Voltage Range Set Point Voltage Tolerance Temperature Variation Line Regulation Vin Vo tol Regtemp Regline Over Io Range Load Regulation Regload Over Io range Total Output Voltage Variation ∆Votot Efficiency η Includes set-point, line, load, –40° ≤Ta ≤ +85°C Io =70% of Iomax –40° ≤Ta ≤ +85°C, Io =Iomin Over Vin range Vo = 5.0V Vo ≤ 3.3V Vo = 5.0V Vo ≤ 3.3V Vo = 5V Vo = 3.3V Vo = 2.5V Vo = 1.8V Vo = 1.5V Vo = 1.4V Vo = 1.2V Vo = 1V Vo ≥ 3.3V Vo ≤ 2.5V Vo Ripple (pk-pk) Vr 20MHz bandwidth Transient Response 0.1A/µs load step, 50% to 75% Iomax Vo over/undershoot Output Adjust ttr ∆Vtr Vadj Over-Current Threshold ITRIP Vin =36V Switching Frequency Under-Voltage Lockout ƒs UVLO Enable On/Off (Pins 1, 2) Input High Voltage Input Low Voltage Input Low Current Standby Input Current Internal Input Capacitance External Output Capacitance VIH VIL IIL Iin standby Cin Cout Isolation Voltage Capacitance Resistance Operating Temperature Range Solder Reflow Temperature Storage Temperature Reliability Ta Treflow Ts MTBF Mechanical Shock — Mechanical Vibration — Weight Flammability — — Vo ≥ 2.5V Vo ≤ 1.8V Vo = 5.0V Vo = 3.3V Vo = 2.5V/1.8V Vo ≤ 1.5V Over Vin range Rising Falling Referenced to –Vin (pin 3) pins 1 & 3 connected Vo =1.0V Vo ≤1.8V Vo ≥2.5V Input–output/input–case Input to output Input to output Over Vin range Surface temperature of module pins or case — Per Bellcore TR-332 50% stress, Ta =40°C, ground benign Per Mil-Std-883D, method 2002.3, 1mS, half-sine, mounted to a fixture Mil-Std-883D, Method 2007.2, Vertical 20-2000Hz, PCB mounted Horizontal — Materials meet UL 94V-0 PT3400 Series Typ Max Units 0 0 0 0 36 — — — — — — — — — — 48 ±1 ±0.8 ±5 ±5 ±1 ±1 16 12 10 7 75 ±2 — ±20 ±15 ±15 (1) ±10 (1) — ±2 ±3 — — — — — — — — — — — — –5 –0 — — — — 250 — — 91 90 89 85 84 84 82 80 50 25 100 ±4 — — 9 12.5 16 20 300 34 32 — — — — — — — — — — — — +5 +10 — — — — 350 — — 5 –0.3 — — — 470 (3) 330 (3) 0 1500 — 10 –40 (4) — –40 — — 0.5 5 1.0 — — — — 1500 — — — — Open (2) +0.4 — — — TBD TBD TBD — — — 85 (5) 215 (6) 125 2.8 — — 106 Hrs — TBD — G’s — — — TBD (7) TBD (7) 34 — — — G’s A VDC %Vo %Vo mV mV mV mV %Vo % mVpp µs %Vo %Vo A kHz V V mA mA µF µF V pF MΩ °C °C °C grams Notes: (1) If the remote sense feature is not being used, –V sense (pin 7) must be connected to –V out (pin 8). (2) The On/Off Enable inputs (pins 1 & 2) have internal pull-ups. They may either be connected to –V in or left open circuit. Leaving pin 1 open-circuit and connecting pin 2 to –Vin allows the the converter to operate when input power is applied. The maximum open-circuit voltage of the Enable pins is 10V. (3) An output capacitor is required for proper operation for all models in which the output voltage is 1.8VDC or less. For models with an output voltage of 2.5V or higher an output capacitor is optional. (4) For operation below 0°C, Cout must have stable characteristics. Use low ESR tantalum capacitors, or capacitors with a polymer type dielectric. (5) See Safe Operating Area curves or contact the factory for the appropriate derating. (6) During reflow of SMD package version do not elevate the module case, pins, or internal component temperatures above a peak of 215°C. For further guidance refer to the application note, “Reflow Soldering Requirements for Plug-in Surface Mount Products,” (SLTA051). (7) The case pins on through-hole pin configurations (N & A) must be soldered. For more information see the applicable package outline drawing. For technical support and more information, see inside back cover or visit www.ti.com Typical Characteristics PT3400 Series 35-W 48-V Input Isolated DC/DC Converter PT3408, 5VDC SLTS164B - JULY 2002 - REVISED OCTOBER 2002 PT3401, 3.3 VDC (See Note A) Efficiency vs Output Current Efficiency vs Output Current VIN 36.0V 48.0V 60.0V 75.0V 80 70 Efficiency - % 60 100 90 VIN 80 36.0V 48.0V 60.0V 75.0V 70 1 2 3 4 5 6 7 60 50 0 2 4 Iout (A) 6 8 10 0 Ripple vs Output Current 20 10 40 VIN 30 75.0V 60.0V 48.0V 36.0V 20 4 5 6 7 2 4 Iout (A) 30 75.0V 60.0V 48.0V 36.0V 20 6 8 0 10 5 2 4 2 1 0 0 3 4 5 6 75.0V 60.0V 48.0V 36.0V 3 1 2 7 4 6 8 10 0 PT3408; VIN =60V PT3401; VIN =60V 200LFM 120LFM 60LFM Nat conv 60 50 40 30 20 Ambient Temperature (°C) Airflow 70 Iout (A) 5 6 7 6 8 10 12 PT3402; VIN =60V 90 80 Airflow 70 200LFM 120LFM 60LFM Nat conv 60 50 40 30 20 4 4 Safe Operating Area (See Note B) 90 3 2 Iout (A) Safe Operating Area (See Note B) 90 2 2 Iout (A) Safe Operating Area (See Note B) 1 75.0V 60.0V 48.0V 36.0V 3 0 2 Iout (A) 0 VIN 4 1 0 80 12 5 Pd - Watts 3 10 VIN Pd - Watts 75.0V 60.0V 48.0V 36.0V 8 6 VIN 4 6 Power Dissipation vs Output Current Power Dissipation vs Output Current 5 1 4 Iout (A) 6 0 2 Iout (A) Power Dissipation vs Output Current Pd - Watts VIN 0 0 6 12 40 0 3 10 10 10 0 8 50 Ripple - mV 30 75.0V 60.0V 48.0V 36.0V Ripple - mV VIN 6 Ripple vs Output Current Ripple vs Output Current 40 2 4 Iout (A) 50 1 2 Iout (A) 50 0 36.0V 48.0V 60.0V 75.0V 70 50 0 VIN 80 60 50 Ambient Temperature (°C) 90 Ambient Temperature (°C) Efficiency - % 90 (See Note A) Efficiency vs Output Current 100 Efficiency - % 100 Ripple - mV PT3402, 2.5 VDC (See Note A) 80 Airflow 70 200LFM 120LFM 60LFM Nat conv 60 50 40 30 20 0 2 4 6 Iout (A) 8 10 0 2 4 6 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 8 10 12 Typical Characteristics PT3400 Series 35-W 48-V Input Isolated DC/DC Converter PT3403, 1.8 VDC SLTS164B - JULY 2002 - REVISED OCTOBER 2002 PT3404/5, 1.5/1.4 VDC (See Note A) Efficiency vs Output Current 100 36.0V 48.0V 60.0V 75.0V 80 70 100 90 VIN 80 36.0V 48.0V 60.0V 75.0V 70 60 3 6 9 12 60 50 0 4 Iout (A) 12 16 0 30 75.0V 60.0V 48.0V 36.0V 20 20 75.0V 60.0V 48.0V 36.0V 10 9 12 5 0 0 4 Iout (A) 8 12 16 0 Power Dissipation vs Output Current Power Dissipation vs Output Current 2 4 2 1 0 0 9 75.0V 60.0V 48.0V 36.0V 3 1 6 5 8 12 16 0 PT3403; VIN =60V PT3404; VIN =60V 200LFM 120LFM 60LFM Nat conv 60 50 40 30 20 Iout (A) 10 12 16 PT3406; VIN =60V 80 Airflow 70 200LFM 120LFM 60LFM Nat conv 60 50 40 30 80 Airflow 70 200LFM 120LFM 60LFM Nat conv 60 50 40 30 20 20 8 12 90 Ambient Temperature (°C) Airflow 70 Ambient Temperature (°C) 80 8 Safe Operating Area (See Note B) 90 6 4 Iout (A) Safe Operating Area (See Note B) 90 4 2 Iout (A) Safe Operating Area (See Note B) 2 75.0V 60.0V 48.0V 36.0V 3 0 4 Iout (A) 0 4 1 0 12 VIN Pd - Watts 3 Pd - Watts 75.0V 60.0V 48.0V 36.0V 16 Power Dissipation vs Output Current VIN VIN 4 12 6 5 5 8 Iout (A) 6 3 4 Iout (A) 6 0 75.0V 60.0V 48.0V 36.0V 10 0 6 VIN 15 5 0 16 20 VIN 15 10 12 25 Ripple - mV VIN Ripple - mV 40 8 Ripple vs Output Current 25 3 4 Iout (A) Ripple vs Output Current Ripple vs Output Current Ripple - mV 8 Iout (A) 50 0 36.0V 48.0V 60.0V 75.0V 70 50 0 VIN 80 60 50 Pd - Watts 90 Efficiency - % VIN Efficiency - % Efficiency - % 90 (See Note A) Efficiency vs Output Current Efficiency vs Output Current 100 Ambient Temperature (°C) PT3406, 1.2 VDC (See Note A) 0 4 8 12 Iout (A) 16 0 4 8 12 16 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 Typical Characteristics PT3400 Series 35-W 48-V Input Isolated DC/DC Converter PT3407, 1.0 VDC SLTS164B - JULY 2002 - REVISED OCTOBER 2002 (See Note A) Efficiency vs Output Current 100 Efficiency - % 90 VIN 36V 48V 60V 75V 80 70 60 50 0 4 8 12 16 Iout (A) Ripple vs Output Current 25 Ripple - mV 20 VIN 75V 60V 48V 36V 15 10 5 0 0 4 8 12 16 Iout (A) Power Dissipation vs Output Current 6 5 Pd - Watts VIN 4 75V 60V 48V 36V 3 2 1 0 0 4 8 12 16 Iout (A) Safe Operating Area (See Note B) PT3406; VIN =60V Ambient Temperature (°C) 90 80 Airflow 70 200LFM 120LFM 60LFM Nat conv 60 50 40 30 20 0 4 8 12 16 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 PT3400 Series Operating Features of the PT3400 Series of Isolated DC/DC Converters Under-Voltage Lockout An Under-Voltage Lock-Out (UVLO) inhibits the operation of the converter until the input voltage is above the UVLO threshold (see the data sheet specification). Below this voltage, the module’s output is held off, irrespective of the state of either the EN1 & EN2 enable controls. The UVLO allows the module to produce a clean transition during both power-up and power-down, even when the input voltage is rising or falling slowly. It also reduces the high start-up current during normal power-up of the converter, and minimizes the current drain from the input source during low-input voltage conditions. The UVLO threshold includes about 1V of hysteresis. If EN2 (pin 2) is connected to -Vin (pin 3) and EN1 (pin 1) is left open, the module will automatically power up when the input voltage rises above the UVLO threshold (see data sheet ‘Standard Application’ schematic). Once operational, the converter will conform to its operating specifications when the minimum specified input voltage is reached. Input Current Limiting The converter is not internally fused. For safety and overall system protection, the maximum input current to the converter must be limited. Active or passive current limiting can be used. Passive current limiting can be a fast acting fuse. A 125-V fuse, rated no more than 5A, is recommended. Active current limiting can be implemented with a current limited “Hot-Swap” controller. Thermal Considerations Airflow may be necessary to ensure that the module can supply the desired load current in environments with elevated ambient temperatures. The required airflow rate may be determined from the Safe Operating Area (SOA) thermal derating chart (see converter specifications). The recommended direction for airflow is into the longest side of the module’s metal case. See Figure 1-1. Figure 1-1 Over-Current Protection To protect against load faults, the PT3400 series incorporates output over-current protection. Applying a load that exceeds the converter’s over-current threshold (see applicable specification) will cause the regulated output to shut down. Following shutdown the module will periodically attempt to automatically recover by initiating a soft-start power-up. This is often described as a “hiccup” mode of operation, whereby the module continues in the cycle of succesive shutdown and power up until the load fault is removed. Once the fault is removed, the converter then automatically recovers and returns to normal operation. Recommended direction for airflow is into (perpendicular to) the longest side Primary-Secondary Isolation Electrical isolation is provided between the input terminals (primary) and the output terminals (secondary). All converters are production tested to a primary-secondary withstand voltage of 1500VDC. This specification complies with UL60950 and EN60950 and the requirements for operational isolation. Operational isolation allows these converters to be configured for either a positive or negative input voltage source. The data sheet ‘Pin-Out Information’ uses shading to indicate which pins are associated with the primary. They include pins 1 through 4, inclusive. For technical support and more information, see inside back cover or visit www.ti.com Application Notes PT3400 Series Adjusting the Output Voltage of the 30W-Rated PT3400 Series of Isolated DC/DC Converters The output voltage of the PT3400 Excalibur™ series of isolated DC/DC converters may be adjusted over a limited range from the factory-trimmed nominal value. Adjustment is accomplished with a single external resistor. The placement the resistor determines the direction of adjustment, either up or down, and the value of the resistor the magnitude of adjustment. Table 3-1 gives the allowable adjustment range for each model in the series as Va (min) and Va (max) respectively. Note that converters with an output voltage of 1.8V or less can only be adjusted up 1. Notes: 1. The output voltage of the PT3401 (3.3V), PT3402 (2.5V), and PT3408 (5V) may be adjusted either higher or lower. All other models, which have an output voltage of 1.8V or less, can only be adjusted higher. 2. Use only a single 1% resistor in either the R1 or (R2) location. Place the resistor as close to the converter as possible. 3. Never connect capacitors to Vo Adj. Any capacitance added to this pin will affect the stability of the converter. Adjust Up: An increase in the output voltage is obtained by adding a resistor, R1 between Vo Adj (pin 6), and –Vsense (pin 7). 4. If the output voltage is increased, the maximum load current must be derated according to the following equation. Adjust Down (PT3401, PT3402, & PT3408 Only): Add a resistor (R2), between Vo Adj (pin 6) and +Vsense (pin 14). Io(max) Refer to Figure 3-1 and Table 3-2 for both the placement and value of the required resistor, R1 or (R2). = (R2) = Where, Va Vo Ro Rs 2 · Ro Va – Vo Ro (Va – 2) Vo – Va – Rs Vo × Io(rated) Va In any instance, the load current must not exceed the converter’s rated output current Io(rated) in Table 3-1. The values of R1 [adjust up], and (R2) [adjust down], can also be calculated using the following formulas. R1 = kΩ – Rs kΩ = Adjusted output voltage = Original output voltage = Resistor constant in Table 3-1 = Internal series resistance in Table 3-1 Figure 3-1 +VIN +VSENSE 14 Remote Sense (+) 4 +V IN 1 +VOUT +VOUT 11–13 (R2) Adj Down EN 1 + PT3400 2 –VIN 3 EN 2 † COUT 330µF R1 Adjust Up –V OUT –V IN –VSENSE SEQ Vo Adj 5 6 8–10 7 For technical support and more information, see inside back cover or visit www.ti.com –VOUT * Remote Sense (–) L O A D Application Notes continued PT3400 Series Table 3-1 DC/DC CONVERTER ADJUSTMENT RANGE AND FORMULA PARAMETERS Series Pt # I o (rated) 4 Vo(nom) Va(min) Va(max) Ω) Ro (kΩ Ω) Rs (kΩ PT3408 7A PT3401 10A 5V 4.75V 5.25V 8.87 66.5 PT3402 12A 3.3V 3.135V 3.465V 9.76 66.5 PT3403 12A PT3404 16A PT3405 16A PT3406 16A PT3407 16A 1.8V N/A 1 1.98V 6.49 66.5 1.5V N/A 1 1.65V 7.5 100.0 1.4V N/A 1 1.54V 7.5 100.0 1.2V N/A 1 1.32V 7.5 100.0 1.0V N/A 1 1.2V 7.5 66.5 2.5V 2.375V 2.625V 10.0 29.4 Table 3-2 DC/DC CONVERTER ADJUSTMENT RESISTOR VALUES Series Pt # PT3408 Vo(nom) Va(req’d) 5V 5.25 5.20 5.15 5.10 5.05 5.00 4.95 4.90 4.85 4.80 4.75 4.5kΩ 22.2kΩ 51.8kΩ 111.0kΩ 288.0kΩ 3.465 3.432 3.399 3.366 3.333 3.330 3.267 3.234 3.201 3.168 3.135 PT3401 PT3402 3.3V 2.5V PT3404 PT3405 PT3406 PT3407 1.8V 1.5V 1.4V 1.2V 1.0V Va(req’d) 1.975 1.950 1.925 1.900 1.875 1.850 1.825 1.800 (457.0)kΩ (191.0)kΩ (102.0)kΩ (57.7)kΩ (31.1)kΩ 1.650 1.625 1.600 1.575 1.550 1.525 1.500 1.475 1.450 1.425 1.400 51.8kΩ 81.4kΩ 131.0kΩ 229.0kΩ 525.0kΩ (308.0)kΩ (116.0)kΩ (51.9)kΩ (19.9)kΩ (0.0)kΩ 2.625 2.600 2.575 2.550 2.525 2.500 2.475 2.450 2.425 2.400 2.375 R1 = Black PT3403 131.0kΩ 171.0kΩ 237.0kΩ 371.0kΩ 771.0kΩ (161.0)kΩ (60.6)kΩ (27.3)kΩ (10.6)kΩ (0.0)kΩ 1.32 1.30 1.28 1.26 1.24 1.22 1.20 1.15 1.10 1.08 1.06 1.04 1.02 1.00 7.7kΩ 20.0kΩ 37.3kΩ 63.3kΩ 107.0kΩ 193.0kΩ 453.0kΩ 0.0kΩ 20.0kΩ 50.0kΩ 100.0kΩ 200.0kΩ 500.0kΩ 20.0kΩ 50.0kΩ 100.0kΩ 200.0kΩ 500.0kΩ 25.0kΩ 50.0kΩ 87.5kΩ 150.0kΩ 275.0kΩ 650.0kΩ 8.5kΩ 33.5kΩ 83.5kΩ 121.0kΩ 184.0kΩ 309.0kΩ 683.0kΩ R2 = (Blue) For technical support and more information, see inside back cover or visit www.ti.com Application Notes PT3400 Series Using the On/Off Enable Controls on the PT3400 Series of DC/DC Converters The PT3400 series of DC/DC converters incorporate two output enable controls. EN1 (pin 1) is the ‘positive enable’ input, and EN2 (pin 2) is the ‘negative enable’ input. Both inputs are electrically referenced to -Vin (pin 3), at the input or primary side of the converter. The enable pins are ideally controlled with an opencollector (or open-drain) discrete transistor. A pull-up resistor is not required. If a pull-up resistor is added, the pull-up voltage must be limited to 15V. The logic truth table for EN1 and EN2 is given in Table 2-1, below. Negative Output Enable (Positive Inhibit) To configure the converter for a negative enable function, EN1 is left open circuit, and the system On/Off control signal is applied to EN2. Applying less than 0.8V (with respect to -Vin ) to EN2, enables the converter outputs. An example of this configuration is provided in Figure 2-2. Note: The converter will only produce an output voltage if a valid input voltage is applied to ±Vin. Figure 2-2; Negative Enable Configuration DC/DC Module Table 2-1; On/Off Enable Logic 1 EN1 (pin 1) EN2 (pin 2) Output Status 0 × Off 1 0 On × 1 Off Logic ‘0’ = –Vin (pin 3) potential Logic ‘1’ = Open Circuit 2 EN 1 EN 2 BSS138 1 =Outputs On –VIN 3 –Vin On/Off Enable Turn-On Time Automatic (UVLO) Power-Up Connecting EN2 to -Vin and leaving EN1 open-circuit configures the converter for automatic power up (see data sheet ‘Standard Application’). The converter control circuitry incorporates an ‘under-voltage lockout’ (UVLO), which disables the converter until a minimum input voltage is present at ±Vin (see data sheet specifications). The UVLO ensures a clean transition during power up and power down, allowing the converter to tolerate a slowly rising input voltage. For most applications EN1 and EN2, can be configured for automatic power-up. Positive Output Enable (Negative Inhibit) To configure the converter for a positive enable function, connect EN2 to -Vin, and apply the system On/Off control signal to EN1. In this configuration, applying less than 0.8V (with respect to -Vin) to EN1 disables the converter outputs. Figure 2-1 is an example of this implemention. The total turn-on time of the module is the combination of a short delay period, followed by the time it takes the output voltage to rise to full regulation. When the converter is enabled from the EN1 or EN2 control inputs, the turn-on delay time (measured from the transition of the enable signal to the instance the outputs begin to rise) is typically 50 milliseconds. By comparison, the rise time of the output voltage is relatively short, and is between 1 and 2 milliseconds. The rise time varies with input voltage, output load current, output capacitance, and the SEQ pin function. Figure 2-3 shows the power-up response of a PT3401 (3.3V), following the removal of the ground signal at EN1 in Figure 2-1. Figure 2-3; PT3401 Enable Turn-On Vo (2V/Div) Figure 2-1; Positive Enable Configuration DC/DC Module 1 2 BSS138 VEN1 (5V/Div) EN 1 EN 2 Delay Time 1 =Outputs Off –VIN 3 –Vin For technical support and more information, see inside back cover or visit www.ti.com HORIZ SCALE: 5ms/DIV Application Notes PT3400 Series Using the Power-Up Sequencing Feature of the PT3400 Series of DC/DC Converters Introduction Power-up sequencing is a term used to describe the order and timing that supply voltages power up in a multi-voltage power supply system. Multi-voltage power supply architectures are a common place requirement in electronic circuits that employ high-performance microprocessors or digital signal processors (DSPs). These circuits require a tightly regulated low-voltage supply for the processor core, and a higher voltage to power the processor’s system interface or I/O circuitry. Powerup sequencing is often required between two such voltages in order to manage the voltage differential during the brief period of power-up. This reduces stress and improves the long term reliability of the dual-voltage devices and their associated circuitry. The most popular solution is termed “Simultaneous Startup,” whereby the two affected voltages both start at the same time and then rise at the same rate. Configuration for Power-up Sequencing The PT3400 series converters have a feature that allows individual modules to be easily configured for simultaneous startup. Using the SEQ control (pin 5), two PT3400 modules are simply interconnected with just a few passive components. This eliminates much of the application circuitry that would otherwise be required for this type of setup. The schematic is given in Figure 4-1. The setup is relatively simple but varies slightly with the combination of output voltages being sequenced. Capacitor C3 (5) is only required when the modules selected are a mix between a high-voltage module (3.3V through 1.8V), and a lowvoltage module (≤1.5V). For all other configurations C3 is replaced by a wire link. For clarification Table 4-1 indicates which modules are a high voltage type (Type A), and which are a low voltage type (Type B). Table 4-2 provides guidance as to the one combination that requires the capacitor C3. Examples of waveforms obtained from a sequenced start-up between two PT3400 series modules are provided in Figure 4-2, Figure 4-3, and Figure 4-4. In each case the voltage difference during the synchronized portion of the power up sequence is typically within 0.4V. Both the timing and tracking of output voltages during the power-up sequence will vary slightly with input voltage, temperature, and with differences in the output capacitance and load current between the two converter modules. This power-up sequencing solution may not be suitable for every application. To ensure compatibility the application should be tested against all variances. For additional support please contact a Plug-in Power applications specialist. Table 4-1; PT3400 Module Type Identification PART No. VOUT TYPE A PT3401 PT3402 PT3403 PT3404 PT3405 PT3406 PT3407 (3.3V) (2.5V) (1.8V) (1.5V) (1.4V) (1.2V) (1.0V) × × × TYPE B × × × × Table 4-2; Value of C3 in Sequencing Setup MODULE #1 MODULE #2 A B A A B B C3 Wire link Wire link 0.1µF (5) COMMENTS Waveforms given in Figure 4-2 Waveforms given in Figure 4-3 Waveforms given in Figure 4-4 Notes 1. The two converters configured for sequenced power up must be located close together on the same printed circuit board. 2. When configured for power-up sequencing, a minimum of 1,000µF output capacitance is recommended at the output of each converter. 3. The best results are obtained if a load of 1A or greater is present at both converter outputs. 4. The capacitors, C1 and C2, should each be placed close to their associated converter, Module #1, and Module #2 respectively. Combining C1 and C2 to a single capacitor of equivalent value is not recommended. 5. The capacitor C3 is only required whenever a Type A and Type B converter are connected together for sequenced power-up. In this event C3 should always be connected to the SEQ control (pin 5) of the Type B module, or the converter with the lowest output voltage. For all other converter configurations C3 is not required, and is replaced by a copper trace or wire link. 6. The capacitors selected for C1, C2, & C3 should be of good quality and have stable characteristics. Capacitors with an X7R dielectric, and 5% tolerance are recommended. 7. The enable controls, EN1 & EN2, are optional for a sequenced pair of converters. If an enable signal is desired, EN1 or EN2 of both converters units must be controlled from a single transistor. For technical support and more information, see inside back cover or visit www.ti.com Application Notes PT3400 Series Figure 4-1; Configuration for Power-Up Sequencing Module #1 (Highest V o) 4 1 2 –V IN 3 +V IN +Sense +V OUT EN 1 14 Remote Sense (+) Vo1 11–13 † C OUT 1,000µF EN 2 –VOUT –VIN –Sense SEQ Vo Adj 5 6 + +V IN LOAD 8–10 7 Remote Sense (–) 14 Remote Sense (+) C1 0.1µF (Note 4) Module #2 (Lowest V o) Q1 BSS138 (Note 8) 1 2 +V IN +Sense +V OUT EN 1 † C OUT 1,000µF EN 2 1 =Inhibit 3 Vo2 11–13 –VOUT –VIN –Sense SEQ Vo Adj 5 6 C3 (Note 5 & Table 4-2) C2 0.1µF (Note 4) For technical support and more information, see inside back cover or visit www.ti.com + 4 LOAD 8–10 7 Remote Sense (–) † For sequencing configurations, a 1,000µF electrolytic capacitor is recommended at the output of each converter. See Note 2. Application Notes PT3400 Series Figure 4-3; Power-Up Sequence Example with Two Type ‘A’ Modules Vo1 (1V/Div) Vo2 (1V/Div) The adjacent plot shows an example of powerup sequencing between two Type ‘A’ modules. In this example the PT3401 (3.3V) and PT3402 (2.5V) are featured. Each converter had a constant current load of 5A applied to its respective output. HORIZ SCALE: 5ms/Div Figure 4-2; Power-Up Sequence Example with Two Type ‘B’ Modules Vo1 (0.5V/Div) Vo2 (0.5V/Div) The adjacent plot shows an example of powerup sequencing between two Type ‘B’ modules. In this example the PT3405 (1.4V) and PT3406 (1.2V) are featured. Each converter had a constant current load of 5A applied to its respective output. HORIZ SCALE: 5ms/Div Figure 4-4; Power-Up Sequence Example Using Type ‘A’ & ‘B’ Modules Vo1 (1V/Div) The adjacent plot shows an example of powerup sequencing between a Type ‘A’ and a Type ‘B’ module. In this example the PT3401 (3.3V) and PT3405 (1.4V) are featured. Each converter had a constant current load of 5A applied to its respective output. Vo2 (1V/Div) HORIZ SCALE: 5ms/Div For technical support and more information, see inside back cover or visit www.ti.com 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. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third–party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright 2002, Texas Instruments Incorporated