PAF600F280 LAMBDA | Alldatasheet
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EiBefore using this product Be sure to take note of precautions and warnings indicated in this manual when using this product. Improper usage may lead to electric shock or fire. Be sure to read this instruction manual thoroughly before using this product Precautions ®@ Avoid touching the baseplate and the case of this product because they get hot. @ There are high voltage and high temperature components within this product. Refrain from disassembling this product or touching its intemal components as this may lead to electric shock or bum. @ To avoid unexpected accident from placing hands or face near the unit during operation. © Confirm connections to input/output terminals and signal terminals are correct as indicated in the instruction manual. @ Attach a fast blow type external fuse to each module to ensure safety operation and compliance to each safety standard approval. @ This power module is designed for professional installation within the end user equipment. @ Output voltage of this product is considered to have hazardous energy level (voltage of 2V and above with power of 240W and above) and must not have physical contact with operator. Protection must be provided on this module when installed on equipment to prevent physical contact with service technician himself or accidentally dropped tools during repair. Before repair, be sure to turn off the input source and confirm that input and output voltage have dropped down to a safe level. @ The application circuits and their parameter are for reference only. Be sure to verify effectiveness of application circuits and their parameters before finalizing circuit design. © The information in this document is subject to change without prior notice. For actual design-in, please refer to the Jatest publications of data sheet, etc., for the most up-to date specifications of the unit. @ No part of this document may be copied or reproduced in any for, or by any mean without prior written consent of Densei-Lambda. ; EH Note: CE Marking CE Marking, when applied to a product covered by instruction manual indicates compliance with the low voltage directive in that is complies with EN60950, DWG. No. : C176-04-11B > a f : Ten olen Piaf A Wacesoon ‘ 4 aFeh of | 7 Feb. ob 7, feb. oF A\\ DENSEI-LAMBDA
M@ Block Diagram Mi Sequence Time Chart M@ Terminal Explanation @ Explanation on Specifications 1. Input Voltage Range 2. Output Voltage Adjustment Range 3. Maximum Output Ripple and Noise 4. Maximum Line Regulation 5. Maximum Load Regulation 6. Over Current Protection (OCP) 7. Over Voltage Protection (OVP) 8. Over Thermal Protection(OTP) 9. Remote Sensing (+S, -S terminal) 10. ON/OFF Control (CNT,SG terminal) 11.‘ Parallel Operation (PC terminal) 12. Series Operation 13. —_‘1.0.G. signal (IOG terminal) 14. Auxiliary power supply for external signals (AUX terminal) 15. Operating Ambient Temperature 16. Operating Ambient Humidity 17. Storage Ambient Temperature 18. Storage Ambient Humidity 19, Cooling Method 20. Baseplate Temperature vs. Output Voltage Drift 21. Withstand Voltage 22. Insulation Resistance 23. Withstand Vibration 24. Withstand Shock MH Before concluding module damage
Vin © = . by O+V c | Si 3 Vino fe} Ov & 5 & g sill 8 e778 zs ° fe} ga 3 © 106 cNTO g 3 eo 8 < & 8 2 © TRIM 8 z 2 5 $c fe) & g 3 O +8 > = 8 . : & © -S a? © PC i <> O AUX Switching Frequency: 200kHz Vin “fey a tnpat vonage | / \\ | Output Voitage! i / i | ; tp eee ee) ee ee ene =P! Move then 100ms i 1 t i i i i 1 1 oe | J | on ia Jo t ft , t ft , t fF fF tt g 8 g§ 6 “ & 8 *1 Level : 4SHS35(V) or Open 0SLS0.8(V) or Short *2 HLevel : 10~13VDC
{ “Vv fo O| -Vin vio O] +Vin “ye Name Plate | +V |O 2} SG | jou e} CNT +v{o evo 9 ie} [Input Side Terminals] [Output Side Terminals] +Vin : +Input Terminal +V + +Output Terminal ~Vin + ~Input Terminal -V : ~Output Terminal [Control Terminals] +8 : +Remote Sensing CNT : ON/OFF Control terminal ~S + ~Remote Sensing SG + ON/OFF Control (ground side) terminal TRIM + Output Voltage Trimming Terminal PC : Output Current Balance Terminal 10G : Inverter Operation Good AUX : Auxiliary Power Supply for External Signals Baseplate can be connected to FG through M3 mounting tapped holes. Connect +Vin,~Vin,+V,~V with consideration of contacting resistance.
- Input Voltage Range Input Fuse Input voltage range for PAF600F280 Series is This power module has no built-in fuse. Use external indicated below. fuse to acquire various Safety Standards and to improve safety. Also, use fast-blow type for every module. Input Voltage Range : 200~400VDC . Input Fuse recommended current rating: 6.3A Basically, ripple voltage (Vrpl) which results from (400VDC) rectification and filtering of commercial AC line is Cl: : included within the input voltage as shown in Fig. 1-1. To prevent the effect of input line inductance to the Ripple voltage must be limited within the voltage Power module, connect electrolytic capacitor or described below. ceramic capacitor between +Vin and —Vin terminals. Furthermore, use electrolytic capacitor with small Allowable input ripple voltage : 20Vp-p ESR value. Especially take note that during line turn off at low ambient temperature, power module output When this value is exceeded, the output ripple will not normally shut down due to unstable C1 voltage. voltage becomes large. Also, ripple current flows across this capacitor. Note that sudden input voltage change may cause Therefore, verify maximum allowable ripple current variation of output voltage transitionally. this capacitor when selecting component. Verify actual Also, input voltage waveform peak value must not _‘Tipple current value by actual measurement. exceed above input voltage range. Recommended capacitor value ‘ +22 uF and above (voltage rating 400V and above) gs Note) 1. Use low impedance electrolytic capacitor with 2 (\\fNf4 Vel Input Voltage excellent temperature characteristics. = LN SL below 20V | ange a 2.When input line inductance becomes = excessively high due to insertion of choke coil, >t operation of the power module could become Time unstable. For this case, increase Cl value more than the value indicated above. Fig.1-1 Ripple Voltage 3. When ambient temperature becomes lower @ Basic Connection than -20°C, connect four capacitors indicated above in parallel because output fall : 50mm 5 characteristics could be affected by ESR. FS avn wot C2, C3 :330pF om a To reduce spike noise voltage at the output, connect jos: the high withstand voltage ceramic capacitor from + <0 -vin v a o- Vin terminal, —Vin terminal to the baseplate. so q ont sam } toad Withstand Voltage of C2,C3 : 3KVac and above OSG Poe Note) 1. Connect the C2 between +Vin terminal and Begeptate 108 g baseplate, and the C3 between ~Vin terminal AUX and baseplate with the short connections as —— possible. Fig.1-2 Basic Connection
- There are cases where output ripple voltage 2.Use capacitors indicated in table 1-1 in could vary according to input wiring method or parallel when ambient temperature becomes peripheral circuits. For this case, increase C2 lower than -20°C because output ripple and C3 value or connect common mode choke voltage could be affected by ESR. coil before Cl. Quantities for capacitors are as follows. C4, C3 : 0.0224 F To reduce spike noise voltage at the output, connect 25V 1,000 x F x 4 parallel @ ceramic capacitor. S0V 820 u F x 2paraliel Withstand voltage of C4,C5 : 500Vde and above SOV 820 u F x 2parallel c he C4 b. y inal and basepl | 4sv_| SOV 1,000 » F x 2 series, x 2parallel onnect the etween +V terminal and baseplate, - . and the C5 between ~V terminal and baseplate with the Tablel-2 C7 Recomm ena vane one ore) short connections as possible. P P 3. Take note of the allowable ripple current of C6:2.2uF the capacitor to be used. Especially, when load. To reduce spike noise voltage at the output, connect adding capacitors for abrupt current changes, a ceramic capacitor between +V and -V within 50mm be sure to verify that ripple current does not distance from the output terminals. exceed allowable ripple current before use. Also, take note that output spike noise voltage could vary according to PCB wiring design. cs: When switches or connectors are used between input C7: . source and PAF600F280 Series input terminals, For stable operation, connect an electrolytic —_ impulse surge voltage is generated at input due to input capacitor between +V and -V at 50mm distance from throw-in by switch on/off or due to inserting/ removing the output terminals. ; of power module from the active line. For this case, Take note that output ripple and output fall connect an additional electrolytic capacitor C8 as characteristics could be affected by electrolytic shown in fig.1-3 and fig. 1-4. capacitor, equivalent impedance and _ inductance characteristics of wiring. Recommended Capacitance Value Take note that output ripple voltage could vary : 10~47 uF and above according to PCB wiring design. (Voltage Rating 400V and above) For cases of abrupt changes in load current or input . . . voltage, increasing capacitance value of the external Also, in-rush current flows at line throw-in. capacitors could reduce the voltage fluctuation. Therefore, be sure to verify capability of switch or fuse to withstand I°t at line throw-in. 12V 25V 1,000 u F x 2 parallel i al 50V 820 uF } vin 28V SOV 820 uF ——— 820uF Fig.1-3 Input Filter with Input Switch SOV 1,000 u F x2 series Tablel-1 C7:Recommended Values of External switeh F Output Capacitor oO Davin Note ) 1.Use low impedance electrolytic capacitor with i] excellent temperature characteristics. | “Vin (Nippon Chemicon LXY Series or equivalent) ots +Vin é| “Vin Fig.1-4 Input Filter when Plural Power
Reverse input connections 2. Output Voltage Adjustment Range Reverse input polarity would cause module damage. Output voltage could be adjusted within the range For cases where reverse connections are possible, comnect described below by external resistor or variable resistor, a protective diode and fuse. Use protective diode with or by applying external voltage. However, take note higher voltage rating than the input voltage, and with that OVP might trigger when output voltage adjustment higher surge current rating than the fuse. exceeds the ranges indicated below. Fuse Output Voltage Adjustment Range oo oO } avin wv -40%~+20% of Nominal Output Voltage ° c | Vin Vv | & Furthermore, when increasing the output voltage reduce the output current so as not to exceed the maximum output power. Fig.J-5 Protection for Reversed Connection of Input __ Also, take note that when output voltage is increased, input voltage range is limited as shown in fig. 2-1. With the external circuit as shown in fig.2-2, remote @ Recommended input filer as EMI countermeasure _Sensing is possible even when output voltage is varied. For (conforms to VCCI Class A, FCC class A) details on remote sensing function, please refer to ”9. Remote Sensing” o-oo +Vin ies es ae eee eee eee ee ee c10 13 s oe Aen o C12. £3) | So -vin Fe ee ee ee Baseplate & i i por dt | / ° “Eo eee ee eee Fig.1-6 Recommended input filer 200 a0 220 mo 360 as EMI countermeasure Input Voltage(VDG) Recommended Values: . os C1 : 2244F Electrolytic Capacitor) Fig.2-1 Limit of Input Voltage C2,C3,C11,C12 : 680pF (Ceramic Capacitor) C9,C10,C13 : 0.68 4 F (Film Capacitor) Output Voltage Adjustment by external resistor or L1 : 5 mH (Common mode choke coil) by variable resistor L2 : 3.8 mH (Common mode choke coil) Resistor values, as well as, connecting methods for external resistor (R1) and external variable resistor (VR) Note) 1. For the power module output, connect output _ are described below. . capacitors described in the basic circuit In this case, using VR as remote programming resistor, connection, remote programming of output voltage can be possible. Also, be sure to connect remote programming resistor 2. VCCI Class A, FCC Class A limits can be between +S terminal and +V terminal. satisfied with the above recommended filter at Densei-Lambda measuring conditions. [| 12v | 2av | 28v | asv | However, there are cases where above limits might not be satisfied due to input VR 100k and output wiring method, as well as, Unit :[Q] peripheral circuits. When selecting input External Resistor : below 5% Tolerance filter, be sure to verify actual EMI Variable Resistor * below+20% Tolerance characteristics (CE and RE) before below 1% Remain finalizing the filter. Refer to PAF600F280-* Evaluation Data for details. Table2-1 Values of External Resistor and Variable Resistor 40% ~ +20% Variable
[__| i2v [ 24v [ 2ev | aav | Error Arpitiog “s 10k 7229 Unit : [Q] External Resistor : below+5% Tolerance 4.205V TRIM Variable Resistor : below+20% Tolerance Reference =92.4kQ 4kQ below 1% Remain Voltage ‘s Table2-2 Values of External Resistor and Variable Resistor +10% Variable Fig.2-4 TRIM Circuit (For the Reference) VR : Load asd 3. Maximum Output Ripple and Noise = Measured value according to the specified methods we : oF based on JEITA-9141 (Clause 7.12 and clause 7.13) which is described in the following. YS O- Measure according to fig.3-1 connection, based on 3 the basic connection of fig.1-2, Connect capacitors tres Gd (C6: ceramic capacitor 2.2 1 F, C7: refer to table 1-1 for electrolytic capacitor values) at 50mm distance from the output terminals. Measure at ceramic Fig.2-2 Example Connection of External Resistor capacitor (C6) leads as shown in fig.3-1 using coaxial cable with JEITA attachment. Use oscilloscope with Output Voltage Adjustment by applying external 100MHz frequency bandwidth or equivalent. voltage Take note that output ripple voltage and output spike By applying external voltage at the TRIM terminal, _"0ise may vary depending on PCB wiring design, output voltage can be adjusted within the same output Generally, output ripple voltage and output spike voltage adjustment range as the output voltage noise can be reduced by increasing capacitance value adjustment by external resistor or variable resistor. For of external capacitor. this case, output voltage can be determined by the formula shown below. vo “le ‘As short as possible Output Voltage = TRIM Terminal Voltage x Nominal Output Voltage ve? 1, +86. >| ' ' D JEITA Attachment | \\ WO ot R:50Q ! ' v 5 O- barwnnsd sO Fig.3-1 Measurement of Maximum Output [4 Ripple & Noise TRIMO << External Voltage 4, Maximum Line Regulation Maximum value of output voltage change when Fig.2-3 Output Voltage Adjustment by input voltage is gradually varied (steady state) within applying external voltage specified input voltage range. For applications other than the above, refer to the trim circuit as shown in fig.2-4 and determine external circuit and component values.
PAF600F280-SERIES © 9 5. Maximum Load Regulation 9. Remote Sensing (+S, -S terminal) Maximum value of output voltage change when Remote sensing terminal is provided to compensate output current is gradually varied (steady state) within for voltage drop across the wirings from the power specified output current range. module output terminal to the load input terminal. When using at dynamic load mode, audible noise When remote sensing function is not used (local sensing), could be heard from the power module and output short +S terminal to +V terminal and, -S terminal to -V voltage fluctuation might increase. A thorough pre- terminal, evaluation must be performed before using this power Take note that voltage compensation range for line drop module. (voltage drop due to wiring) is determined such that output Voltage at the output terminals is within output voltage range and that voltage between —V and ~S terminals is within 2V 6. Over Current Protection (OCP) or less. Even for remote sensing case, use power module This power module has built-in OCP function. such that output power is within specified maximum output Output will recover when short circuit or overload power. Furthermore, reduce noise effect by using shield wire, conditions are released. OCP setting value is fixed and twist pair, or parallel pattem. therefore, cannot be externally adjusted. Also, take note that power module might be damaged continuing output short circuit or over load +SQ.__ Stabilize the output voltage at conditions depending on thermal conditions. ay terminal Load +wO O+ 7. Over Voltage Protection (OVP) It WF KIOOOOOOOO This power module has built-in OVP function. po OVP set point is relative to the rated output voltage ve 9- value. When OVP is triggered, output can be recovered by } turning input line off and then turning it on again after s input voltage drops down to OV, or by manual reset of the control ON/OFF terminal. Reset time for ON/OFF terminal is 100ms or longer. Fig.9-1 Remote Sensing at Use When verifying OVP function by applying external voltage at the output terminals, applied voltage value should not exceed specified OVP maximum value. Refer to specification table for OVP maximum value. asd Stabilize the output voltage at Avoid applying external voltage that exceeds OVP ‘output terrinal Load maximum value because this wili cause power module j Leo damage. wo O+ OVP setting value is fixed and cannot be adjusted ‘fo externally. vo - i L_ 8. Over Thermal Protection (OTP) s? This power module has built-in OTP function. This — function operates and shuts down the output when ambient temperature or internal temperature of power module Fig.9-2 Remote Sensing Not in Use abnormally rises. OTP operates at 105°C to 130°C baseplate temperature.. When OTP is triggered, output can be recovered by . turning input line off and then turning it on again after 10. ON/OFF Control (CNT, SG terminal) input voltage drops down to OV, or by manual reset of Without turning the input supply on and off, the the control ON/OEF terminal, after temperature output can be enable and disabled using this function. sufficiently decreased. Reset time for ON/OFF ON/OFF control circuit is on the input side (the terminal is 100ms or longer. primary side), and CNT terminal pin is used. Use the SG terminal as ground for CNT terminal.
If this function is not used, short the CNT terminal 12. Series Operation and the SG terminal. Series operation is possible for PAF600F280 series. Connections shown fig. 12-land fig. 12-2 i jbl 1) The maximum impressed voltage for the CNT mn 6 8 ¥S possible terminal is 35V and the maximum reverse voltage . is 0.7V. Also the source current for CNT terminal is +s J about ImA. wo o* When wiring becomes long, connect a capacitor fe about 0,1F value between the CNT and the SG vom terminal at a nearest distance. s a 2) ON/OFF terminal can be controlled by opening or Load closing connections (with switch or relay), or by 8 a) photo-coupler ON/OFF. wor Also for the secondary control, isolation can be E; achieved through the use of a photo-coupler or vO O- equivalent. s a) * When using photo-coupler, connect between the CNT and the SG terminal to make transistor Fig-12-1 Series Operation in High Output side shortest. Voltage Fuse +Vin + +8 a w $+ Vi z Load “Vin ct . : hs Ss CNT wv + Fig.10-1 CNT,SG terminal connection ‘esd v - s CNT Level [ Output Status | H(4Vand above ) or Open ; ; ; L (0.8Vand below or short Fig.12-2 Output Series Operation Table 10-1 ON/OFF Control Mode . . 13. L.0.G. signal (1OG terminal) Normal or abnormal operation of the power module 11. Parallel Operation (PC terminal) can be monitored by using the 1OG terminal. Output of By connecting the PC terminal of each power this signal monitor is located at secondary side (output module, output current can be equally drawn from each _Side) and is an open collector output. . module. A maximum of 11 units of the same model can This signal is LOW when inverter is normally be connected, operating and HIGH when inverter stops or when Furthermore, be sure that the output power of every _‘iuverter_ is operating abnormally. (maximum sink module does not exceed the maximum output power value. current is SmA, maximum applied voltage is 35V) By setting output voltage accuracy of each module Ground for the IOG terminal is the-S terminal. in a parallel operation to within ++1%, the maximum _Also note that IOG becomes unstable for following value of the output current that can be drawn is 95% of conditions: : the total rated output current, ‘Operation of Over Current Protection (OCP) Refer to “Parallel Operation” of the PH-Series “Light load conditions at parallel operation Application Notes for details, *Dynamic load operation
14, Auxiliary power supply for external For better improvement of power module reliability, signals (AUX terminal) derating of baseplate temperature when using is For AUX terminal, output voltage value is within 10 recommended. ~14VDC range, maximum output current is 20mA. Ground for the AUX terminal is ~S terminal. . . . Avoid short circuit of AUX terminal with other 16. Operating Ambient Humidity terminals as this would lead to power module damage. Take note that moisture could lead to power module abnormal operation or damage. 15. Operating Ambient Temperature There is no restriction on mounting direction but 17. Storage Ambient Temperature there should be enough consideration for airflow so Abrupt temperature change would cause moisture that heat does not accumulate around the power formation that leads to poor solderabilty of each module vicinity. Determine external components terminal of the power module. configuration and mounting direction on PCB such that air could flow through the heatsink at forced cooling and conventional cooling. . eae By maintaining actual baseplate temperature below 18. Storage Ambient Humidity 100°C, operation is possible. Take enough care when storing the power module For details on thermal design, refer to Application because rust which causes poor solderability would form Notes “Thermal Design”, in each terminal when stored in high temperature, high humidity environment. Note) 1. Maximum baseplate temperature is 100°C. For worst case operating condition, verify baseplate temperature at measurement point 19. Cooling Method indicated in fig. 15-1. Operating temperature range is specified by the baseplate temperature. Therefore, several method of oe Pat heat dissipation is possible. SN For details on thermal design, refer to Application Notes a8 “ ion” eS Temperature ‘Thermal Design”. cai “~s2}Measuring Point of Baseplate Fig.15-1 Temperature Measurement 20. Baseplate Temperature vs. Output Point of Baseplate Voltage Drift Output voltage drift is defined as the rate of voltage change when baseplate temperature only is changed 2. There is limitation on baseplate temperature during operation. range for as shown in fig.15-2. soot 21. Withstand Voltage PoP By This power module is designed to have a withstand 80% fe-e-e-beecece dere esedee eens eteeeeee dh \\ voltage of 2.5kVAC between input and baseplate, and i : i i i i \\ 3kVAC between input and output for 1 minute, E os vor frvvenedecnnne hanseesseesFrseees ebooee When conducting withstand voltage test during 3 : i ! i i i incoming inspection, be sure to set the current limit an ve 1 2a, ee q value of the withstand voltage testing equipment to 20% feveee Tee VosBVVin> SHOW) =e 20mA. rr H This power module is designed to have a withstand on re! value of 500VDC between output and baseplate for 1 “40-2020 = 6100 Baseplate Temperature (°C) minute. When conducting withstand voltage test during Fig.15-2 Derating curve incoming inspection, be sure to apply DC voltage. ll
Be sure to avoid conducting test with AC voltage vO because this would cause power module damage. * [) Furthermore, avoid throw in or shut off of the testing (° CNT VPS equipment when applying or when shutting down the oan 825 test voltage. Instead, gradually increase or decrease the O+Vvin sO applied voltage. Take note especially not to use the (hy, 0 true . timer of the test equipment because when the timer Withstand [) . . : . Voltage tester_| Baseplate PcO switches the applied voltage off, impulse voltage which poo ©) i.) has several times the magnitude of the applied voltage + 08s is generated causing damage to the power module. @ C2) AUXO) Connect the terminals as shown in fig.21-1, fig.21-2 1 fig.21-3. — and fig . . . S00VDC 1minute When conducting test by the basic connection shown Fig.21-3 Withstand Voltage Tester for in fig.1-2, connect the terminals similarly. Output-Baseplate wd 22. Insulation Resistance ent , 2) Use DC insulation tester (MAX 500V) between O . [) output and baseplate. Insulation resistance value is voles ster con +s PS 100MQ and above at S00VDC applied voltage. Also (wr -S' LS take note that depending on the insulation tester used, O-vin TRMC} some testers generate high voltage pulse. Discharge © pC bd the power module after test using a resistor, etc. BasePlate bd © 1oG' +O AUX! JJ (° CNT wv = Ose +sO 2.5KVAC Iminute (20mA) CO in s jd Fig.21-1 Withstand Voltage Tester for on jd Input-Baseplate vin TRM Isolation Tester | Bageplate Pc! &2 — © [J 1 loeQ g 52 wd ~) AUX) H cnt wv & t Withstand Gs SG 48 e) Over 100MQ at 500VDC Vottage tester ( J [) Fig.22-1 Isolation Test (° +Vin s PS -vin TRMO) ©) rede 23. Withstand Vibration BasePlate () Refer to Application Notes “Mounting Method” © los PS section. AUxO 24, Withstand Shock Fen eae avenue we Withstand shock value is defined to be the value at ig.21-2 Withstand Voltage Tester for : ae Input-Output Densei Lambda shipment and packaging conditions.
Verify following items before concluding power 4) Load regulation and line regulation is large module damage. + Is specified input voltage applied? + Are the input terminals and the output terminals 1) No output voltage firmly connected? + Is specified input voltage applied? + Is the measurement done at the sensing points? + Are the ON/OFF control terminal (CNT, SG), remote + Is the input or output wire too thin? sensing terminal (+S, -S), output voltage trimming terminal (TRIM) correctly connected? 5) Output ripple voltage is large + Is output current of the auxiliary power supply for + Is the measuring method used the same or equivalent external signals terminal (AUX) within the specified with the specified method in the Application Notes? value ? + Is the input ripple voltage value within the specified + For cases where output voltage adjustment is used, is value? the resistor or variable resistor setting, connections correctly done? + Are there no abnormalities in the output load used? + Is the baseplate temperature within the specified temperature range? 2) Output voltage is high + Are the remote sensing terminals (+S, -S) correctly connected? + Is the measurement done at the sensing points? + For cases where output voltage adjustment is used, is the resistor or volume setting, connections correctly done? 3) Output voltage is low + Is specified input voltage applied? + Are the remote sensing terminals (+S, -S) correctly connected? + Is the measurement done at the sensing points? + For cases where output voltage adjustment is used, is the resistor or variable resistor setting, connections correctly done? + Are there no abnormalities in the output load used?