fm front end ka22497/d introduction the ka22497 is a monolithic integrated circuit designed for the fm front end of portable radio cassettes or music centers. it consists of rf amp, local osc buffer and mixer. compared with conventional types, it is improved in the following characteristics: ? low supply voltage ? strong input ? spurious radiation features ? wide supply voltage range: v cc = 1.6 v ~ 6.0 v ? low local oscillation stop voltage: v stop = 0.9 v(typ) ? improved inter-modulation characteristics by double balanced type mixer circuit ? low spurious radiation ? built-in clamping diode in the mixer output stage ordering information device package operating temperature ka22497 9-slp -25 c ~+75 c KA22497D 14-sop 9-sip 14-sop block diagram figure 1. 1 3 4 5 6 7 8 rf amp rf bypass rf mix in gnd mix osc osc 9 osc buff mix local osc v ref output output v cc input output (8) (11) (12) (13) (14) (3) (4) (5) (7) 2 note : ( ) means KA22497D
ka22497/d fm front end absolute maximum ratings (ta = 25 c) note : derated above ta = 25 c in the proportion of 4mw/ c electrical characteristics (ta = 25 c, v cc = 5 v, f = 98mhz, fm = 1khz, d f = + 22.5khz, unless otherwise specified) characteristic symbol value unit supply voltage v cc 8 v power dissipation p d ka22497 600 mw KA22497D 300 operating temperature t opr - 25 ~ +75 c storage temperature t stg - 55 ~ +150 c characteristic symbol test conditions min typ max unit quiescent circuit current i ccq v l = 0 ? 5.0 8.0 ma -3db limiting sensitivity v i(lim) vd (vi = 60 db m )-3db down ? 3.0 7.0 db m conversion gain g v v i = 60 db m 25 31 ? db usable sensitivity s usa s/n = 30db ? 11 ? db m oscillation voltage v osc f osc = 108mhz 90 165 250 mv oscillation stop voltage v stop ? ? 0.9 1.3 v
fm front end ka22497/d test circuit (i ccq , v i(lim) , s usa , g v , v osc , v stop ) figure 2. when using the ka22471 for the if stage. figure 3. 1 2 3 4 5 6 7 8 9 b.p.f fm s.g z o =75 w 4.7p KA22497D c.f t3 0.01 m v osc 150p t2 15p 0.01 m 100 m v cc ( ): KA22497D t1 15p 1000p + 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 ka2247 0.047 m 0.047 m 68k + v cc am section af out + 1 m 0.015 m 100 m t4 (8) (11) (12) (13) (14) (3) (4) (5) (7) 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 ka22471 c.f 6 t3 22 m 22 m + + v cc + af out 0.015 m 4.7k 0.047 m 0.01 m 0.01 m t5 1 m
ka22497/d fm front end coil specifications (bottom view) t1 fm rf t2 fm osc t3 fm ift t4 fm ift (det) t5 fm ift (det) * f (mhz) q o turns 98 100 4 * in a diameter of 5.5 mm 0.8 mm f uew * * in a diameter of 5.5 mm 0.8 mm f uew 3 2 1 4 5 6 0.12 mm f uew co (pf) f (mhz) q o turns 1 - 3 1 - 3 1 - 3 4 - 6 75 10.7 115 12 1 korea toko 4 6 3 2 1 0.12 mm f uew co (pf) f (mhz) q o turns 1 - 3 1 - 3 1 - 3 56 10.7 95 12 korea toko 4 6 3 2 1 0.12 mm f uew co (pf) f (mhz) q o turns 4 - 6 4 - 6 4 - 6 47 10.7 115 14 korea toko f (mhz) q o turns 98 100 3
fm front end ka22497/d 100 0 -100 -200 0 2 4 6 8 10 0 v cc (v), supply voltage local oscillation frequency deviation, local oscillation voltage.suply voltage d f ( k h z ) , l o c a l o s c i l l a t i o n f r e q u e n c y d e v i a t i o n d f v osc 300 200 100 v o s c ( m v ) , l o c a l o s c i l l a t i o n v o l t a g e 300 200 100 0 ta( c), ambient temperature local oscillation voltage ambient temperature 0 20 40 60 80 -20 v o s c ( m v ) , l o c a l o s c i l l a t i o n v o l t a g e v cc = 5v f osc = 108mhz 10 8 2 0 0 2 4 6 8 10 v cc (v), supply voltage quiescent circuit current-supply voltage i c c q ( m v ) , q u i e s c e n t c i r c u i t c u r r e n t 4 6 v i = 0 40 30 0 0 2 4 6 8 10 v cc (v), supply voltage sensitivity-supply voltage 10 20 f = 98mhz fm = 1khz d f = 22.5khz dev. s usa v i(lim) v i ( l i m ) ( d b m ) , - 3 d b l i m i t i n g s e n s i t i v i t y s u s a ( d b m ) , u s a b l e s e n s i t i v i t y 40 30 0 -20 0 20 40 60 80 ta( c ), ambient temperature sensitivity-ambient temperature 10 20 v cc = 5v f = 98 mhz d f = 22.5khz dev. v i ( l i m ) ( d b m ) , - 3 d b l i m i t i n g s e n s i t i v i t y s u s a ( d b m ) , u s a b l e s e n s i t i v i t y s usa v i(lim) 200 100 -200 -20 0 20 40 60 80 ta( c ), ambient temperature ambient temperature temperature 100 0 v cc = 5v f = 98 mhz fm = 1khz dev. d f ( 1 k h z ) , l o c a l o s c i l l a t i o n f r e q u e n c y d e v i a t i o n local oscillation frequency deviation fm = 1khz
ka22497/d fm front end application information 1. rf amp the rf amp is a common base type, so the operating frequency range is improved. the gnd of the bypass capacitor (pin 2) should be located closely at pin 5 (gnd). when using the bypass capacitor at v cc -line of pin 3. we can expect an improvement of the s/n ratio. figure 4. 2. mixer the mixer stage uses a double balanced type in order to protect the leakage of osc, spurious radiation. also, this is built into the limiter in order to improve the strong input characteristic. figure 5. b. p. f fm ant 75 w 75 w 1 2 3 bias v cc 1000p 15p t1 v cc if amp v cc osc out bias mix out mix in 6 4
fm front end ka22497/d local oscillation the local oscillator uses a colpitts oscillator for stable oscillation at high frequency. this is built into the osc buffer in order to stably operate the osc frequency and osc voltage at strong input. figure 6. v cc osc buff mix 8 15p 15p
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