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october 2012 doc id 023723 rev 1 1/16 AN4172 application note ieee802.3af class 3 poe converter reference design high efficiency flyback converter based on the pm8800a by antonio rotta introduction the pm8800a is a highly integrated device embedding an ieee802.3af compliant powered device (pd) interface together with a pwm controller and support for auxiliary sources. this document focuses on a reference design for a high efficiency, class 3 pd (up to 13 w input) power converter based on a flyback topology with pulse transformer driven synchronous rectification using the pm8800a as the main controller. schematics of the poe converter are given in section 2 , while the related bill of material is detailed in section 3 . in section 4 efficiency measurements together with main waveforms of the poe interface and power converter are shown. www.st.com
contents AN4172 2/16 doc id 023723 rev 1 contents 1 electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1 efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2 waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2.1 startup sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2.2 primary side mosfet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.2.3 secondary side mosfet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2.4 load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2.5 output ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
AN4172 electrical specifications doc id 023723 rev 1 3/16 1 electrical specifications table 1. specifications for 3.3 v output parameter description min. typ. max. unit input voltage range applied at rj45 connector 0 57 v operative input voltage 42 57 v uvlo vin rising edge 36 v vin falling edge 30 v auxiliary input voltage range 42 48 56 v output voltage (vout) vin = 42 v to 57 v, iout 0 to imax 3.25 3.35 3.45 v output current (iout) vin = 42 v to 57 v 0 3.5 a peak-to-peak output ripple 48 vin, iout = imax 30 50 mvpp efficiency dc-dc only vin = 48 v, iout = imax 90 % overall efficiency vin = 48 v, iout = imax 88 % switching frequency 150 khz
schematics AN4172 4/16 doc id 023723 rev 1 2 schematics figure 1. high efficiency poe converter schematic: detail of the input section including data transformers and terminations input output d a t a tr a n s former u s e s td ieee 8 02. 3a f d a t a tr a n s former termin a tion typic a l v a l u e for re s i s tor 75 ohm typic a l v a l u e for c a p a citor 10nf ch ass i s ch ass i s ch ass i s ch ass i s ch ass i s ch ass i s c d b a c4 t b d 060 3 100v c4 r 3 0 t b d 060 3 j2 rj45 d a t a j a ck 1 2 3 4 5 6 7 8 9 10 c2 t b d 060 3 100v r2 t b d 060 3 t2 h2019/tla-6t127lf 1 2 3 6 7 8 9 10 11 14 15 16 4 5 12 1 3 c5 t b d 060 3 100v c6 t b d 1 8 12 2kv r 3 t b d 060 3 r6 t b d 060 3 r4 t b d 060 3 c 8 t b d 1 8 12 2kv r7 t b d 060 3 r5 t b d 060 3 rj45 d a t a a nd power j a ck 1 2 3 4 5 6 7 8 9 10 t1 h2019/tla-6t127lf 1 2 3 6 7 8 9 10 11 14 15 16 4 5 12 1 3 c 3 t b d 060 3 100v r1 t b d 060 3 am12950v1
AN4172 schematics doc id 023723 rev 1 5/16 figure 2. high efficiency poe converter: flyback topology with pulse transformer driven synchronous rectification auxii dc power j a ck auxi dc power j a ck 3 . 3 5v 3 .5a rcla ss dccl c s t r v ss vcc gnd comp agnd ss npgd gd auxi_irl auxii gnd agnd gnd gnd gnd gnd agnd agnd c d a b d 3 1 bat46j s od 3 2 3 r 33 510 c45 0.1 u f c0 8 05 r 3 9 0.22 ohm 1206 c14 1 u f 1206 100v r 3 5 52r 3 0 8 05 1 % d 3 9 bat46j s od 3 2 3 c 3 1 nm d7 nm s tth1r02a s ma r11 nm 0 8 05 c25 1 u f 16v 060 3 r 3 6 10k r29 6 8 0 d1 8 s tp s 1h100a s ma d24 s tp s 1h100a s ma d22 s tp s 1h100a s ma r26 10 c16 6 8 pf 0 8 05 100v r24 0r d25 s tp s 1h100a s ma r44 12.4k 1 % d20 s tp s 1h100a s ma c1 8 10 u 1206 16v c2 3 10 u 1206 16v r2 3 nm c49 10nf coilcraft poe1 3 p- 33 l t 3 3 2 1 4 8 9 10 7 c27 nm c0 8 05 t7 coilcraft da2 3 19-al 4 6 3 1 0. 33u h l2 do1 8 1 3 h- 33 1ml 1 2 r16 56 1206 r 3 4 51k 1 % r47 nm 1 % c11 1nf 0 8 05 c10 nm 0 8 05 r 38 100k d2 8 bat46j s od 3 2 3 d19 s tp s 1h100a s ma d2 3 s tp s 1h100a s ma r15 nm 0 8 05 r27 nm c 3 9 0.1 u f c2 8 0.1 u f u 3 t s 4 3 1 s ot2 3 -5 3 5 4 1 2 c15 1 u f 1206 100v r 3 2 21k 1 % c 3 4 0.1 u f r 8 nm 2512 r 3 1 22 r0 8 05 r10 nm 0 8 05 c 3 0 1 u f 16v 060 3 10 u h m ss 7 3 41- 10 3 ml l1 1 2 c 3 5 100pf r2 8 6 8 0 r4 3 3 . 3 1k 1 % c12 nm 0 8 05 r22 10k d15 bat46j s od 3 2 3 c59 1 u f 16v 060 3 r21 270k 1 % r12 nm 0 8 05 q7 mmbt 3 906 s ot2 3 r19 100k d4 nm s tth1r02a s ma d21 s tp s 1h100a s ma j4 j4 1 2 3 c 3 2 47nf c1 3 22 u 100v 8 x10.2 d5 nm bzx 8 4c15 s ot2 3 1 3 2 c24 33 0 u 8 x10.5 6. 3 v c1 0.1 u f 0 8 05 100v c41 nm 0 8 05 100v c 3 6 0.1 u nm 0 8 05 100v d14 bat46j s od 3 2 3 bat46j s od 3 2 3 d40 q1 s i4 8 4 8 s o 8 4 5 1 2 3 d 3 s maj5 8 a r1 3 1r0 1206 c19 10 u 1206 16v r1 8 47 r1 8 47 q 3 nm s t s 10pf 3 0l s o 8 4 5 1 6 7 8 2 3 2.2n 1 8 12 2kv c29 r5 3 47 r0 8 05 d 3 0 bat46j s od 3 2 3 u1 pm 88 00a ht ss op16 rt 1 ss 2 auxii 3 vin 4 c s 1 3 comp 14 vfb 15 agnd 16 rcla ss 5 auxi_irl 6 dccl 7 gnd 9 gd 10 vcc 11 npgd 12 ex p a d 17 v ss 8 r 3 7 nm 1 % c44 0.1 u f c0 8 05 c 3 7 47nf u2 s h a rp pc 3 h7 4 1 2 3 d29 bat46j s od 3 2 3 c26 0.1 u f q6 mmbt 3 906 s ot2 3 nm 1206 16v c21 c20 nm 1206 16v j 3 1 2 3 q2 s t s 11n 3 llh5 s o 8 4 5 1 2 3 d16 nm bat46j s od 3 2 3 c 33 470p am12951v1
bill of material AN4172 6/16 doc id 023723 rev 1 3 bill of material table 2. bill of material qty. reference description value tol. voltage body vendor 1 c1 ceramic capacitor 100 nf 100 v 603 tdk 4 c2, c3, c4, c5 ceramic capacitor tbd 10% 100 v 603 tdk 2 c6, c8 ceramic capacitor tbd 2 kv 1812 tdk 1 c11 ceramic capacitor 1 nf 10% 100 v 805 tdk 1 c13 aluminium capacitor 22 f 20% 100 v 810x10.2 std low esr 2 c14, c15 ceramic capacitor 1 f 20% 100 v 1206 tdk 1 c16 ceramic capacitor 68 pf 100 v 805 tdk 3 c18, c19, c23 ceramic capacitor 10 f 6.3 v 805 tdk 1 c24 aluminium capacitor 330 f 6.3 v 8x10.2 std low esr 3 c25,c30, c59 ceramic capacitor 1 f 20% 16 v 603 std 6 c26, c28, c34, c39, c44, c45 ceramic capacitor 100 nf 20% 50 v 603 std 1 c29 ceramic capacitor 2.2 nf 2 kv 1812 tdk 2 c32, c37 ceramic capacitor 47 nf 50 v 603 std 1 c33 ceramic capacitor 470 pf 50 v 603 std 1 c49 ceramic capacitor 10 nf 20% 50 v 603 std 1 d3 tvs diode smaj58a sma st 9 d14, d15, d28, d29, d30, d31, d39, d40 schottky diode bat46j 100 v sod323 st 8 d4, d7, d8, d9, d12, d13, d14, d17 schottky diode stps1h100a 100 v sma st 1 l1 smt inductor 10 h mss7341- 103ml coilcraft 1 l2 smt inductor 0.33 h do1813h- 331ml coilcraft 1 q1 mosfet, n ch. si 4848 150 v so8 vishay 1 q2 mosfet, n ch. sts11n3llh5 30 v so8 st 2 q6, q7 transistor, pnp mmbt3906lt1 40 v sot23 std 8 r1, r2, r3, r4, r5, r6, r7, r30 chip resistor tbd 603 std
AN4172 bill of material doc id 023723 rev 1 7/16 1 r13 chip resistor 1r0 1206 std 1 r16 chip resistor 56 1206 std 2 r18, r53 chip resistor 47 603 std 1 r19 chip resistor 100 k 805 std 1 r21 chip resistor 270 k 1% 603 std 2 r22, r36 chip resistor 10 k 603 std 1 r24 chip resistor 0 r 603 std 1 r26 chip resistor 10 r 603 std 2 r28, r29 chip resistor 680 603 std 1 r31 chip resistor 22 603 std 1 r32 chip resistor 21 k 1% 603 std 1 r33 chip resistor 510 603 std 1 r34 chip resistor 51 k 1% 603 std 1 r35 chip resistor 52r3 1% 603 std 1 r38 chip resistor 100 k 603 std 1 r39 chip resistor 0.22 r 603 std 1 r43 chip resistor 3.31 k 1% 603 std 1 r44 chip resistor 12.4 k 1% 603 std 2 t1, t2 poe+ magnetics h2019 pulse 1 t3 power transformer poe13p-33l coilcraft 1 t7 gate driver transformer da2319-al coilcraft 1 u1 poe controller pm8800a htssop16 st 1 u2 smt optocoupler pc3h7 4pdip sharp 1 u3 shunt regulator ts431ailt sot23-5 st table 2. bill of material (continued) qty. reference description value tol. voltage body vendor
test results AN4172 8/16 doc id 023723 rev 1 4 test results 4.1 efficiency measurements figure 3. efficiency measurements at 48 v input the difference between dc-dc and overall measurements is about 2% from 1 a to full load. in figure 3 it is possible to see the contribution to the total losses of the pd interface section of the converter; the major contribution comes from the rectification bridge. 50 % 52 % 54 % 56 % 5 8% 60 % 62 % 64 % 66 % 6 8% 70 % 72 % 74 % 76 % 7 8% 8 0 % 8 2 % 8 4 % 8 6 % 88% 90 % 92 % 94 % 96 % 9 8% 100 % 0.00 0.50 1.00 1.50 2.00 2.50 3 .00 efficiency io u t (a) i s ol a ted s ynchrono us fly ba ck converter with pm 88 00a over a ll dcdc + h s inp u t s t a ge am12952v1
AN4172 test results doc id 023723 rev 1 9/16 4.2 waveforms 4.2.1 startup sequence figure 4. startup from the cisco catalyst 3750e switch with 3 a load figure 5. startup from the powerdsine 9001gr.at injector with 3 a load
test results AN4172 10/16 doc id 023723 rev 1 figure 6. startup from the phihong psa16u-480.af injector with 3 a load 4.2.2 primary side mosfet figure 7. primary side power mosfet waveforms at 0 a load
AN4172 test results doc id 023723 rev 1 11/16 figure 8. primary side power mosfet waveforms at 3 a load 4.2.3 secondary side mosfet figure 9. secondary side power mosfet waveforms at 0 a load
test results AN4172 12/16 doc id 023723 rev 1 figure 10. secondary side power mosfet waveforms at 3 a load 4.2.4 load transient figure 11. response of the converter to a 1.5 a - 3 a load transient
AN4172 test results doc id 023723 rev 1 13/16 4.2.5 output ripple figure 12. output ripple measurement at 3 a figure 13. output ripple measurement at 3 a with infinite persistence
test results AN4172 14/16 doc id 023723 rev 1 figure 14. output ripple measurement at 0 a
AN4172 revision history doc id 023723 rev 1 15/16 5 revision history table 3. document revision history date revision changes 02-oct-2012 1 initial release.
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