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PT7708 Datasheet(PDF) 3 Page - Texas Instruments |
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PT7708 Datasheet(HTML) 3 Page - Texas Instruments |
3 / 4 page Application Notes For technical support and more information, see inside back cover or visit www.ti.com/powertrends PT7708/PT7709, PT7742/PT7743 Capacitor Recommendations for the PT7708/09 Regulators and PT7742/43 Current Boosters Input Capacitors The recommended input capacitance is determined by 1.4 ampere minimum ripple current rating and 1500µF minimum capacitance. Capacitors listed below must be rated for a minimum of 2x the input voltage with +5V operation. Ripple current and ≤100mΩ Equivalent Series Resistance (ESR) values are the major considerations along with temperature when selecting the proper capacitor. Output Capacitors The minimum required output capacitance is 330µF with a maximum ESR less than or equal to 100m Ω. Failure to observe this requirement may lead to regulator instability or oscillation. Electrolytic capacitors have poor ripple per- formance at frequencies greater than 400kHz, but excellent low frequency transient response. Above the ripple fre- quency ceramic decoupling capacitors are necessary to improve the transient response and reduce any microproces- sor high frequency noise components apparent during higher current excursions. Preferred low ESR type capaci- tor part numbers are identified in the Table 1 below. Note: (N/R) is not recommended for this application, due to extremely low Equivalent Series Resistance (ESR) Table 1 Capacitors Characteristic Data Tantalum Characteristics Tantalum capacitors with a minimum 10V rating are recommended on the output bus, but only the AVX TPS Series, Sprague 594/595 Series, or Kemet T495/T510 Series. The AVX TPS Series, Sprague Series or Kemet Series capacitors are specified over other types due to their higher surge current, excellent power dissipation and ripple current ratings. As an example, the TAJ Series by AVX is not recommended. This series exhibits considerably higher ESR, reduced power dissipation and lower ripple current capability. The TAJ Series is a less reliable compared to the TPS series when determining power dissipation capability. Capacitor Table Table 1 identifies the characteristics of capacitors from a number of vendors with acceptable ESR and ripple current (rms) ratings. The suggested minimum quantities per regu- lator for both the input and output buses are identified. This is not an extensive capacitor list. The table below is a selection guide for input and output capacitors. Other capacitor vendors are available with comparable RMS ripple current rating and ESR (Equivalent Series Resistance at 100kHz). These critical parameters are necessary to insure both optimum regulator performance and long capacitor life. r o t i c a p a Cr o t i c a p a C r o t i c a p a C r o t i c a p a Cr o t i c a p a C / r o d n e V/ r o d n e V / r o d n e V / r o d n e V/ r o d n e V s e i r e Ss e i r e S s e i r e S s e i r e Ss e i r e S s c i t s i r e t c a r a h C r o t i c a p a Cs c i t s i r e t c a r a h C r o t i c a p a C s c i t s i r e t c a r a h C r o t i c a p a C s c i t s i r e t c a r a h C r o t i c a p a Cs c i t s i r e t c a r a h C r o t i c a p a Cy t i t n a u Qy t i t n a u Q y t i t n a u Q y t i t n a u Qy t i t n a u Q g n i k r o Wg n i k r o W g n i k r o W g n i k r o Wg n i k r o W e g a t l o Ve g a t l o V e g a t l o V e g a t l o Ve g a t l o V ) F µ ( e u l a V) F µ ( e u l a V ) F µ ( e u l a V ) F µ ( e u l a V) F µ ( e u l a Vt n e l a v i u q E ) R S E (t n e l a v i u q E ) R S E ( t n e l a v i u q E ) R S E ( t n e l a v i u q E ) R S E (t n e l a v i u q E ) R S E ( e c n a t s i s e R s e i r e Se c n a t s i s e R s e i r e S e c n a t s i s e R s e i r e S e c n a t s i s e R s e i r e Se c n a t s i s e R s e i r e S m u m i x a M C ° 5 0 1m u m i x a M C ° 5 0 1 m u m i x a M C ° 5 0 1 m u m i x a M C ° 5 0 1m u m i x a M C ° 5 0 1 e l p p i Re l p p i R e l p p i R e l p p i Re l p p i R ) s m r I ( t n e r r u C) s m r I ( t n e r r u C ) s m r I ( t n e r r u C ) s m r I ( t n e r r u C) s m r I ( t n e r r u C l a c i s y h Pl a c i s y h P l a c i s y h P l a c i s y h Pl a c i s y h P ) m m ( e z i S) m m ( e z i S ) m m ( e z i S ) m m ( e z i S) m m ( e z i S t u p n It u p n I t u p n I t u p n It u p n I s u Bs u B s u B s u Bs u B t u p t u Ot u p t u O t u p t u O t u p t u Ot u p t u O s u Bs u B s u B s u Bs u B r e b m u N r o d n e Vr e b m u N r o d n e V r e b m u N r o d n e V r e b m u N r o d n e Vr e b m u N r o d n e V c i n o s a n a P C F g t M e c a f r u S A F V 6 1 V 5 3 V 0 1 V 6 1 0 0 2 2 0 3 3 0 8 6 0 0 8 1 8 3 0 . 0 Ω 5 6 0 . 0 Ω Ω 0 9 0 . 0 Ω 2 3 0 . 0 A m 0 0 0 2 A m 5 0 2 1 A m 5 5 7 A m 0 0 0 2 5 . 6 1 x 8 1 5 . 6 1 x 5 . 2 1 5 . 2 1 x 0 1 5 1 x 8 1 1 1 1 1 1 1 N 2 2 2 C 1 C F V E E Q L 1 3 3 V 1 C F V E E 1 8 6 A 1 A F U E E A 2 8 1 C 1 A F U E E d e t i n U n o C - i m e h C s e i r e S V F L V 5 2 V 6 1 V 6 1 0 3 3 0 0 2 2 0 7 4 4 8 0 . 0 Ω 8 3 0 . 0 Ω 4 8 0 . 0 Ω 2 4 0 = 2 / Ω A m 5 2 8 A m 0 3 6 1 2 x A m 5 2 8 6 1 x 0 1 0 2 x 6 1 6 1 x 0 1 1 1 1 1 L L 6 1 X 0 1 M 1 3 3 B V 5 2 V X L L L 0 2 X 6 1 M 2 2 2 B V 6 1 V X L L L 6 1 X 0 1 M 1 7 4 B V 6 1 V X L n o c i h c i N s e i r e S L P s e i r e S M P V 0 1 V 0 1 V 5 2 0 8 6 0 0 8 1 0 3 3 0 9 0 . 0 Ω 4 4 0 . 0 Ω 5 9 0 . 0 Ω A m 0 7 7 A m 0 2 4 1 A m 0 5 7 5 1 x 0 1 5 1 x 6 1 5 1 x 0 1 1 1 1 1 6 H H M 1 8 6 A 1 L P U 6 H H M 2 8 1 A 1 L P U 6 H P M 1 3 3 E 1 L P U S S n o c s O V S V 0 1 V 0 1 0 3 3 0 3 3 6 0 0 . 0 = 4 / W 5 2 0 . 0 Ω 5 0 0 . 0 = 4 / 0 2 0 . 0 Ω A m 0 0 8 9 > A m 0 0 8 9 > 5 . 0 1 x 0 1 6 . 2 1 x 3 . 0 1 4 4 R / N ) e t o N ( M 0 3 3 S S 0 1 g t M e c a v f u S ( M 0 3 3 V S 0 1 X V A m u l a t a n a T s e i r e S - S P T V 0 1 V 0 1 0 3 3 0 3 3 0 2 = 5 / 0 0 1 . 0 Ω 0 6 0 . 0 Ω A m 0 0 5 3 A m 6 2 8 1 x L 3 . 7 x W 3 . 4 H 1 . 4 5 5 1 1 0 0 1 0 R 0 1 0 M 7 3 3 V S P T 0 6 0 0 R 0 1 0 M 7 3 3 V S P T e u g a r p S m u l a t n a T D 4 9 5 / D 5 9 5 V 0 1 V 0 1 0 3 3 0 8 6 1 1 0 . 0 = 4 / W 5 4 0 . 0 Ω 0 9 0 . 0 Ω A m 0 0 5 4 > A m 0 6 6 1 > x L 3 . 7 x W 7 . 5 H 0 . 4 5 2 1 1 T 2 R 0 1 0 0 X 7 3 3 D 4 9 5 t n u o M e c a f r u S T 2 R 0 1 0 0 X 7 8 6 D 5 9 5 t e m e K m u l a t n a T 5 9 4 T / 0 1 5 T s e i r e S V 0 1 V 0 1 0 3 3 0 2 2 5 3 0 . 0 Ω 0 7 0 . 0 Ω 5 3 0 . 0 = 2 / Ω A m 0 0 0 2 A m 0 0 0 2 > L 3 . 7 x W 3 . 4 H 0 . 4 x 5 6 1 2 S A 0 1 0 M 7 3 3 X 0 1 5 S A 0 1 0 M 7 2 2 X 5 9 4 T t n u o M e c a f r u S p a c s o P o y n a S B P T V 0 10 2 20 4 0 . 0 Ω A m 0 0 0 3x L 2 . 7 x W 3 . 4 H 1 . 3 62 M 0 2 2 B P T 0 1 t n u o M e c a f r u S |
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