View MP6001DN_6721254.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

mp6001 monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 1 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. the future of analog ic technology description the mp6001 is a monolithic flyback/forward dc-dc converter which includes a 150v power switch and is capable of delivering up to 15w output power. it can also be used for boost and sepic applications. the mp6001 uses the fixed-frequency peak current mode primary controller architecture. it has an internal soft-start, auto-retry, and incorporates over current, short circuit, and over-voltage protection. the mp6001 can also skip cycles to maintain zero load regulation. it has a direct optocoupler interface which bypasses the internal error amplifier when an isolated output is desired. the mp6001 is ideal for telecom applications, and is available in a compact, thermally enhanced soic8 package with an exposed pad. features ? integrated 0.9 ? 150v power switch ? cycle-by-cycle current limiting ? programmable switching frequency ? duty cycle limiting with line feed forward ? integrated 100v startup circuit ? internal slope compensation ? disable function ? built-in soft-start ? line under voltage lockout ? line over voltage protection ? auto-restart for opened/shorted output ? zero load regulation ? thermal shutdown applications ? telecom equipment ? voip phones, power over ethernet (poe) ? distributed power conversion ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application mp6001 line comp fb vcc 8 5 1 7 2 4 3 6 sw rt gnd vin d2 b330a d1 1n4148 r3 c3 10nf tl431 mp6001_tac_s01 pc357 +v in 36v~72v -v in v out 5v @ 3a 90 80 70 60 50 40 30 20 10 0 efficiency (%) 0 0.5 1.0 1.5 2.0 2.5 3.0 load current (a) mp6001-ec01 efficiency vs load current v in = 48v v in = 75v v in = 36v v out = 5v
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 2 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. ordering information part number* package top marking free air temperature (t a ) MP6001DN soic8e MP6001DN -40 c to +85 c * for tape & reel, add suffix ?z (eg. MP6001DN?z). for rohs compliant packaging, add suffix ?lf (eg. MP6001DN?lf?z) package reference gnd line fb comp sw vin vcc rt 1 2 3 4 8 7 6 5 top view mp6001_pd01_soic8n absolute maxi mum ratings (1) v sw ..............................................-0.5v to +180v v in ..............................................-0.3v to +120v all other pins ...............................-0.3v to +6.5v continuous power dissipation? (t a = +25c) (2) ?????????????????......2.5w junction temperature ...............................150c lead temperature ....................................260c storage temperature............... -65c to +150c recommended operating conditions (3) supply voltage v cc ...........................4.5 v to 6v output voltage v sw .....................-0.5v to +150v input voltage v in .........................+10v to +100v operating junct. temp (t j )...... -40 c to +125 c thermal resistance (4) ja jc soic8e .................................. 50 ...... 10... c/w notes: 1) exceeding these ratings may damage the device. 2) the maximum allowable power dissipation is a function of the maximum junction temperature t j (max), the junction-to- ambient thermal resistance ja , and the ambient temperature t a . the maximum allowable continuous power dissipation at any ambient temperature is calculated by p d (max) = (t j (max)-t a )/ ja . exceeding the maximum allowable powe r dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circuitry protects the device from permanent damage. 3) the device is not guaranteed to function outside of its operating conditions. 4) measured on jesd51-7 4-layer board.
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 3 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. electrical characteristics v cc = 5.0v, v line = 1.8v, rt = 10k, t a = +25 c, unless otherwise noted. parameter symbol condition min typ max units quiescent supply current i cc 1.2v < v line < 3.2v, v fb = 1.3v 1.0 1.5 ma line ov threshold voltage v cc = 5.0v 2.85 3 3.15 v line ov hysteresis v cc = 5.0v 300 mv line uv threshold voltage v cc = 5.0v 1.16 1.21 1.26 v line uv hysteresis v cc = 5.0v 100 mv v cc upper threshold voltage 5.75 6.0 6.25 v v cc lower threshold voltage 4.30 4.50 4.70 v v cc over voltage threshold voltage 6.3 6.6 6.9 v feedback voltage v fb 1.16 1.21 1.26 v feedback input current i fb v fb = 1.2v 50 na error amplifier gain bandwidth (5) gbw 1 mhz error amplifier dc gain (5) a v 60 db comp output source current i oh v fb = 1.0v, v comp = 0.5v 2 ma comp output sink current i ol v fb = 1.4v, v comp = 2.5v 2 ma switch-on resistance r on v sw = 0.1v 0.9 ? switch leakage current i lk v sw = 150v 1 a minimum oscillating frequency f min rt = 100k 55 khz maximum oscillating frequency f max rt = 10k 550 khz thermal shutdown (5) 150 c thermal shutdown hysteresis (5) 30 c current limit (5) i lim 2 a startup current i st v in = 20v, v cc = 4.0v 3 ma note: 5) guaranteed by design, not production tested. pin functions pin # name description 1 gnd ground. power return and reference node. 2 line uv/ov set point. short to gr ound to turn the controller off. 3 fb regulation feedback input. inverting input of the er ror amplifier. the non-inverting is internally connected to 1.2v 4 comp error amplifier output. 5 rt oscillator resistor and synchronous clock pin. connect an external resistor to gnd for oscillator frequency setting. it can be used as a sy nchronous input from external oscillator clock. 6 vcc supply bias voltage. a capacitor no less than 1uf is recommended to connect between gnd. 7 vin high voltage startup circuit supply. 8 sw output switching node. high voltage power n- channel mosfet drain output. the internal start bias current is supplied from this pin.
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 4 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical performanc e characteristics v in = 48v, v out = 5v, t a = +25oc, unless otherwise noted. v sw 100v/div. v out ac coupled 50mv/div. i l 1a/div. mp6001-tpc01 steady state test v in = 48v, v out = 5v, i out = 2.7a 4ms/div. mp6001-tpc07 start-up through enable v in = 48v, v out = 5v, i out = 2.7 resistive load mp6001-tpc05 mp6001-tpc04 duty cycle vs line voltage v sw 100v/div. v out 2v/div. v cc 2v/div. i l 1a/div. 100ms/div. mp6001-tpc06 short circuit test over current hiccup at v in = 48v, i out = 4.4a v out 1v/div. v sw 50v/div. v cc 2v/div. i trans 1a/div. 4ms/div. mp6001-tpc08 shut-down through enable v in = 48v, v out = 5v, i out = 2.7a resistive load v out 2v/div. v sw 20v/div. v sync 2v/div. i trans 1a/div. mp6001-tpc02 synchronize programmable oscillator f sw = 54khz, 60khz of sync signal is applied to rt pin. mp6001-tpc03 synchronize programmable oscillator f sw = 54khz, 500khz of sync signal is applied to rt pin. v out 2v/div. v sw 20v/div. v sync 2v/div. i trans 1a/div. 70 60 50 40 30 20 1.0 1.5 2.0 2.5 3.0 line voltage (v) maximum duty cycle (%) v out 1v/div. v sw 50v/div. v cc 2v/div. i trans 1a/div. v out ac coupled 50mv/div. i load 1a/div.
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 5 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. operation the mp6001 uses programmable fixed- frequency, peak current-mode pwm with a single-ended primary architecture to regulate the output voltage. the mp6001 incorporates features such as protection circuitry and an integrated high voltage power switch into a small 8-pin soic. this product targets high performance, cost effective dc-dc converter applications. -- + -- + -- -- + + 1.2v ea 1.0v 1.2v 3.0v ovlo 6.5v 4.5v uvlo error amplifier pwm comparator current limit comparator current sense slope comp clock -- + -- + -- + thermal monitor soft-start current limit osc leb 5 3 4 2 rt mp6001_bd01 fb comp line regulator ibias ref 6 8 1 vcc sw gnd startup control logic 7 vin figure 1?functional block diagram
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 6 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. high voltage startup the mp6001 features a 100v startup circuit, see figure 1. when power is applied, the capacitor at the vcc pin is charged through the vin pin. when the voltage at the vcc pin crosses 6.0v without fault, the controller is enabled. the vcc pin is then disconnected from the vin pin and v cc voltage is discharged via the operating current. when v cc drops to 4.5v, the vcc pin is reconnected to the vin pin and v cc will be recharged. the voltage at the vcc pin repeats this ramp cycle between 4.5v and 6.0v. vin needs to be higher than 10v in order to keep high voltage startup circuit working properly. this can be guaranteed by setting input uvlo 10v. it is also recommended that the capacitor at vcc pin be no less than 1uf to achieve stable operation. the vcc pin can be powered with a voltage higher than 4.5v from an auxiliary winding to reduce the power dissipated in the internal start-up circuit. the vcc pin is internally clamped at 8v. under-voltage and over-voltage detection the mp6001 includes a line monitor circuit. two external resistors form a voltage divider from the input voltage to gnd; its tap connects to the line pin. the controller is operational when the voltage at the uv/ov pin is between 1.2v and 3v. when the voltage at the uv/ov pin goes out of this operating range, the controller is disabled and goes into standby mode. the line pin can also be used as a remote enable. grounding the uv/ov pin will disable the controller. error amplifier the mp6001 includes an error amplifier with its non-inverting input connected to internal 1.2v reference voltage. the regulated voltage is fed back through a resistor network or an optocoupler to the fb pin. figure 2 shows some common error amplifier configurations. -- + 1.2v fb c2 c3 r3 comp vcc c1 primary winding r1 r2 d1 ea 34 6 -- + 1.2v fb comp vcc mp6001_f02 c2 r2 r3 (a) using primary winding to provide feedback (b) feedback is from secondary (common collector) (c) feedback is from secondary (common emitter) ea 34 6 -- + 1.2v fb comp vcc ea 34 6 c2 figure 2?error amplifier configurations
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 7 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. synchronize programmable oscillator the mp6001 oscillating frequency is set by an external resistor from the rt pin to ground. the value of rt can be calculated from: s f khz 550 k 10 rt = the mp6001 can be synchronized to an external clock pulse. the frequency of the clock pulse must be higher than the internal oscillator frequency. the clock pulse width should be within 50ns to 150ns. the external clock can be coupled to the rt pin with a 100pf capacitor and a peak level greater than 3.5v. duty cycle limiting with line feed forward the mp6001 has a d max (maximum duty cycle) limit at 67.5% when the line pin voltage is equal to 1.3v. as v line increases, d max reduces. maximum duty cycle can be calculated by: % 100 v v 7 . 2 v 7 . 2 d line max ? ? ? ? ? ? + = limiting the duty cycle at high line voltage protects against magnetic saturation and minimizes the output sensitivity to line transients. auto-restart when v cc is biased from an auxiliary winding and an open loop condition occurs, the voltage at the vcc pin increases to 6.5v. when v cc crosses the threshold voltage, the auto-restart circuit turns off the power switch and puts the controller in standby mode. when v cc drops to 4.5v, the startup switch turns on to charge v cc up again. when v cc crosses 6.0v, the switch turns off and the standby current discharges v cc back to 4.5v. after repeating the ramp cycles between the two threshold voltages 15 times, the auto-restart circuit is disabled and the controller begins soft-start.
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 8 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. application information switching frequency the frequency (f s ), has big effects on the selection of the transformer (tr), the output cap, (c2), and the input cap, (c1). the higher the frequency, the smaller the sizes for tr, c2, and c1. however, a higher frequency also leads to higher ac power losses in the power switch, control circuitry, transformer, and in the external interconnection. the general rule states that lower the output power, higher the optimum switching frequency. for low current (<10a) applications, f s is usually 200khz to 300khz if synchronous rectifiers are used and 300khz to 500khz if schottky rectifiers are used. fundamental equations the transformer turns ratio n is defined as: s p n n n = where n p and n s are the number of turns of the primary and secondary side windings, respectively. the output voltage v o is estimated to be: n v d 1 d v in o ? = where d is the duty cycle. the steady-state drain to source voltage of the primary power switch when it is off is estimated as: o in ds v n v v + = the steady-state reverse voltage of the schottky diode d2 is estimated as: n v v v in o 2 d + = the output current is calculated as: ) d 1 ( i i d o ? = where i d is the average current through schottky diode when it is conducting. the input current is calculated as: d i i s in = where i s is the average current through the primary power switch when it is conducting. transformer (coupled inductor) design 1. transformer turns ratio the transformer turns ratio determines the duty cycle range, selection of the rectifier (d2), primary side peak current, primary snubber loss, and the current as well as voltage stresses on the power switch (s). it also has effects on the selection of c1 and c2. a higher transformer turns ratio (n) means the following: ? higher duty cycle ? higher voltage stress on s (v ds ), but lower voltage stress on d2 (v d2 ). ? lower primary side rms current (i s(rms) ), but higher secondary side rms current (i d2(rms) ). ? use of a smaller input capacitor but bigger output capacitor. ? lower primary side peak current (i s(peak) ) and lower primary snubber loss. ? lower main switch (s) turn-on loss for a 5v power supply design, with v in =36v~75v, below table shows the voltage stresses of the power switch (s) and the rectifier (d2). table 1?main switch (s) and rectifier (d2) voltage stress vs. transformer turns ratio n d max v ds (v) v ds /0.9 (v) v d2 (v) v d2 /0.9 (v) 4 0.36 119 132 38 42 5 0.41 125 139 32 36 6 0.45 131 146 28 31 7 0.49 138 153 25 28 8 0.53 144 160 23 26 9 0.56 150 167 21 24 10 0.58 156 174 20 22 11 0.60 163 181 19 21 note: the voltage spike due to the leakage inductance of the transformer and device?s voltage rating/derating factors were considered. see power switch selection and snubber design for more information.
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 9 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. 2. ripple factor of the magnetizing current the conduction loss in s, d2, the transformer, the snubber, and in the esr of the input/output capacitors will increase as the ripple of the magnetizing current increases. the ripple factor (k r ) is defined as the ratio of the peak-to-peak ripple current vs. the average current as shown in figure 3. m m r i i k = where i m can be derived either from input or output current; ) d 1 ( n i d i i 0 in m ? = = mp6001_f03 i m i m i d2 /n t s dt s 0 figure 3?magnetic current of flyback transformer (reflected to primary side) the input/output ripple voltage will also increase with a high ripple factor, which makes the filter bigger and more expensive. on the other hand, it can help to minimize the turn-on loss of s and reverse-recovery loss due to d2. with nominal input voltage, k r can be selected at 60%~120% for most dc-dc converters. the primary side (or magnetizing) inductance can be determined by: m r s in f i k t d v l = 3. core selection pick a core based on experience or through a catalog (refer to http://www.ferroxcube.com). select an er, eq, pq, or rm core to minimize the transformer?s leakage inductance. 4. winding selection solid wire, litz wire, pcb winding, flex pcb winding or any combination thereof can be used as transformer winding. for low current applications, solid wire is the most cost effective choice. consider using several wires in parallel and interleaving the winding structure for better performance of the transformer. the number of primary turns can be determined by: e max p f p a b i l n = where b max is the allowed maximum flux density (usually below 300mt) and a e is the effective area of the core. the air gap can be estimated by: f e 2 o l a n gap = 5. right half plane zero a flyback converter operating in continuous mode has a right half plane (rhp) zero. in the frequency domain, this rhp zero adds not only a phase lag to the control characteristics but also increases the gain of the circuit. typical rule of thumb states that the highest usable loop crossover frequency is limited to one third the value of the rhp zero. the expression for the location of the rhp zero in a continuous mode flyback is given by: 2 f 2 load rhpz n d l 2 ) d 1 ( r f ? = where r load is the load resistance, l f is the magnetizing inductance on transformer primary side, and n is the transformer?s turn ratio. reducing the primary inductance increases the rhp zero frequency which results in higher crossover frequencies.
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 10 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. duty cycle range the duty cycle range is determined once n is selected. in general, the optimum operating duty cycle should be smaller for high input/low output than low input/high output applications. except for high output voltage or wide input range applications, the maximum d usually does not exceed 60%. voltage stress of the internal power switch & external schottky diode for the internal power switch, the voltage stress is given by: p o in ds v n v v v + + = where v p is a function of l lk (leakage inductrance), f s , r, c, c ds , v in , i o , etc. please refer to figure 4. the lower the l lk and io, the lower the vp. smaller r can reduce vp, but power loss will increase. see snubber design for details. typically v p can be selected as 20~40% of (v in +nv o ). -- + -- + c2 i d2 l lk i s c r d v ds v ds v c v p v in 0 v c c1 s t r d2 mp6001_f04 figure 4?key operation waveform for the rectifier, d2, the voltage stress is given by: 2 pd in o 2 d v n v v v + + = use of a r-c or r-c-d type snubber circuit for d2 is recommended. 2 pd v can be selected as 40~100% of (v o +v in /n), thus: ) nv v ( k v 0 ) max ( in s ) max ( ds + = where k s =1.2~1.4, and ) n v v ( k v ) max ( in 0 2 d ) max ( 2 d + ? = where k d2 =1.4~2. for example, v 23 ) 8 v 75 v 5 ( 6 . 1 v v 144 ) v 5 8 v 75 ( 25 . 1 v v 5 v , 6 . 1 k , 25 . 1 k , 8 n , v 75 v 2 d ds o 2 d s ) max ( in = + = = + = = = = = = so the power switch rating should be higher than 144v, and the rated voltage for the synchronous rectifier or schottky diode should be higher than 23v. snubber design (passive) snubber for power switch figure 5 shows four different ways to clamp the voltage on the power device. rcd type of snubber circuit is widely used in many applications. s (a) (b) (c) (d) d z r d r d c d c d d z s s s mp6001_f05 figure 5?snubber designs
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 11 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. rcd type of snubber design procedure: 1. setting v p higher v p means higher voltage stress on the power switch, but lower power loss. usually, v p can be set as 20%~40% of (v in + nxv o ). v ds v p v in n x v o 0 v c mp6001_f06 figure 6?voltage waveform of primary power switch shown in figure 5(c) 2. estimated rcd snubber loss is given by: ) v v n 1 ( p p p o lk loss _ rcd + = where: c 2 p lk lk f i l 2 1 p = p lk is the energy stored in the leakage inductance (l lk ), which carries the peak current at the power switch turn-off. 3. calculate values of the r d and c d of rcd snubber by: loss _ rcd 2 p d p v r = s d d f 1 c r >> input capacitor the input capacitors (c1) are chosen based upon the ac voltage ripple on the input capacitors, rms current ratings, and voltage rating of the input capacitors. for a given ac ripple voltage, v in_pp , c1 can be derived from: pp _ in s in v t ) d 1 ( i 1 c ? = v in_pp may affect the c1 voltage rating and converter stability. c1 rms current has to be considered: d ) d 1 ( i i in 1 c _ rms ? = c1 has to have enough rms current rating. output filter the simplest filter is an output capacitor (c2), whose capacitance is determined by the output ripple requirement. the current waveform in the output capacitor is mostly in rectangular shape. the full load current is drawn from the capacitors during the primary switch on time. the worse case for the output ripple occurs under low line and full load conditions. the ripple voltage can be estimated by: s o c pp 0 f 2 c d i v = ? ? esr also needs to be specified for the output capacitors. this is due to the step change in d2 current results in a ripple voltage that is proportional to the esr. assuming that the d2 current waveform is in rectangular shape, the esr requirement is then obtained by given the output ripple voltage. ) d 1 ( esr i v o r _ pp o esr ? = ? the total ripple voltage can be estimated by: esr _ pp o c pp o pp o v v v ? ? ? ? + =
mp6001 ? monolithic flyback/forward dc-dc converter mp6001 rev. 0.92 www.monolithicpower.com 12 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. control design generally, telecom power supplies require the galvanic isolation between a relatively high input voltage and low output voltages. the most widely used devices to transfer signals across the isolation boundary are pulse transformers and optocouplers. -- + -- + s tr d d r6 r3 rb r4 r1 r2 r5 c1 v ref v cc r load r esr c o v o tl431 v in -- + mp6001_f07 figure 7?simplified circuit of isolated power supply with optocoupler feedback the mp6001 uses current mode control to achieve easy compensation and fast transient response. a type ii compensation network which has two poles and one zero is needed to stabilize the system. the practical compensation parameters are provided in the ev6001dn datasheet. boost controller application the mp6001 can be used as a boost controller as shown in figure 8. mp6001 gnd comp fb line 8 5 6 7 1 4 3 2 sw rt vcc vin mp6001 _f08 v in c3 10nf d1 200v/1a 180v 20ma figure 8?high voltage led boost controller circuit
mp6001 ? monolithic flyback/forward dc-dc converter notice: the information in this document is subject to change wi thout notice. please contact m ps for current specifications. users should warrant and guarantee that third party intellectual property rights ar e not infringed upon when integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp6001 rev. 0.92 www.monolithicpower.com 13 5/5/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. package information soic8e see detail "a" 0.0075(0.19) 0.0098(0.25) 0.050(1.27) bsc 0.013(0.33) 0.020(0.51) seating plane 0.000(0.00) 0.006(0.15) 0.051(1.30) 0.067(1.70) top view front view side view bottom view note: 1) control dimension is in inches. dimension in bracket is in millimeters. 2) package length does not include mold flash, protrusions or gate burrs. 3) package width does not include interlead flash or protrusions. 4) lead coplanarity (bottom of leads after forming) shall be 0.004" inches max. 5) drawing conforms to jedec ms-012, variation ba. 6) drawing is not to scale. 0.089(2.26) 0.101(2.56) 0.124(3.15) 0.136(3.45) recommended land pattern 0.213(5.40) 0.063(1.60) 0.050(1.27) 0.024(0.61) 0.103(2.62) 0.138(3.51) 0.150(3.80) 0.157(4.00) pin 1 id 0.189(4.80) 0.197(5.00) 0.228(5.80) 0.244(6.20) 14 85 0.016(0.41) 0.050(1.27) 0 o -8 o detail "a" 0.010(0.25) 0.020(0.50) x 45 o 0.010(0.25) bsc gauge plane

▲Up To Search▲

Price & Availability of MP6001DN

	To Download MP6001DN Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .