SC2446A Semtech Corporation, SC2446A Datasheet
SC2446A
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SC2446A Summary of contents
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... The Step-down controllers oper- ate from an input of at least 4.7V and are capable of regulating outputs as low as 0.5V The step-down controllers in the SC2446A have the pro- vision to sense inductor R voltage drop for current-mode DC control ...
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... SC2446A www.DataSheet4U.com ...
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... SC2446A www.DataSheet4U.com ± ...
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... < I < < < SC2446A www.DataSheet4U.com ...
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... Only available in tape and reel packaging. A reel BST1 contains 2500 devices for TSSOP package. GDH1 (2) Lead free product. This product is fully WEEE and RoHS compliant. GDL1 PVCC PGND GDL2 GDH2 BST2 VPN2 VIN2 AVCC SS2/EN2 5 SC2446A www.DataSheet4U.com ...
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... DSBL1 Overload OCN1 Hiccup Control 1 0.5 (REFOUT) CLK2 SEL 0.5 (REFIN) ANALOG SWITCH PWM2 Soft-Start OL2 And DSBL2 Overload OCN2 Hiccup Control 2 0.5 (REFIN) Figure 3. SC2446A Block Diagram 8 SC2446A www.DataSheet4U.com REFERENCE 0.5V 0.5V UVLO 4.3/4. SEL Y www.semtech.com AVCC 16 BST1 26 GDH1 25 VPN1 27 GDL1 24 PGND 22 SS1/EN1 ...
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... POWER MANAGEMENT Block Diagram IN- 0.5(V ) REFOUT / 0.5(V ) REFIN SS/EN UVLO Figure 4. Soft-Start and Overload Hiccup Control Circuit 2005 Semtech Corp. OCN - + 0.5V/3.2V 0.8V/1.2V 9 SC2446A www.DataSheet4U.com DSBL www.semtech.com ...
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... EM interference. Minimum Switch On Time Consideration In the SC2446A the falling edge of the clock turns on the top MOSFET gate. The inductor current and the sensed voltage ramp up. After the sensed voltage crosses a threshold determined by the error amplifier output, the top MOSFET gate is turned off ...
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... Rosc (k Ohm) Figure 5. Free running frequency vs. R Inductor (L) and Ripple Current Both step-down controllers in the SC2446A operate in synchronous continuous-conduction mode (CCM) regardless of the output load. The output inductor selection/design is based on the output DC and transient requirements. Both output current and voltage ripples are reduced with larger inductors but it takes longer to change the inductor current during load transients ...
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... The total equivalent ESR is not simply the parallel combination of all the individual ESR’s either. Instead they should be calculated using the following formulae. 12 SC2446A www.DataSheet4U.com . The RMS current ripple rating should also ...
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... Capacitors with low ESL should be used also important to place the input capacitor close to the MOSFETs on the PC board to reduce trace inductances around the pulse current loop. The RMS value of the capacitor current is approximately 13 SC2446A www.DataSheet4U.com and the input capacitor C has an ESR ...
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... The two step-down channels of the SC2446A operate at 180 degrees from each other. If both step- down channels in the SC2446A are connected in parallel, both the input and the output RMS currents will be reduced. Ripple cancellation effect of interleaving allows the use of smaller input capacitors ...
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... In the current mode control as implemented in SC2446A, the voltage ripple critical for PWM operation fact, the AC voltage ripple peak-to-peak value of V ...
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... The voltage feedback gain h=0.5/V value as Once either R calculated for the desired output voltage V number of standard resistance values is limited, the calculated resistance may not be available as a standard value resistor result, there will be a set error in the 16 SC2446A www.DataSheet4U.com ...
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... Semtech Corp. The inner current-loop is unstable (sub-harmonic oscillation) unless the inductor current up-slope is steeper than the inductor current down-slope. For stable operation above 50% duty-cycle, a compensation ramp is added to the sensed-current. In the SC2446A the compensation ramp is made duty-ratio dependent. The compensation ramp is approximately ...
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... If the converter crossover frequency is set around 1/ the switching frequency parameters then can be calculated where, (260 µ use SC2446A www.DataSheet4U.com T(s)=G (s)C(s). vc << and specifies the loop crossover noted that the crossover frequency c g hkR ...
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... The load f 5 × transient response behavior is further tested and measured to meet the specification. 19 SC2446A www.DataSheet4U.com ...
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... The followings are suggested for proper layout. Power Stage 1) Separate the power ground from the signal ground. In SC2446A, the power ground PGND should be tied to the source terminal of lower MOSFETs. The signal ground AGND should be tied to the negative terminal of the output capacitor. ...
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... POWER MANAGEMENT Typical Application Schematic 2005 Semtech Corp. 21 SC2446A www.DataSheet4U.com www.semtech.com ...
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... SC2446A www.DataSheet4U.com Channel 1: Vo1 = 2.5V Channel 2: Vo2 = 1. fic fic erm als erm als erm als 1 ...
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... POWER MANAGEMENT Typical Characteristics (Cont.) Ch1 (2.5V) Output voltage ripple = 14.0mV p-p Ch2 (1.2V) Output voltage ripple = 15.6mV p-p 2005 Semtech Corp. 23 SC2446A www.DataSheet4U.com www.semtech.com ...
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... POWER MANAGEMENT Typical Characteristics (Cont.) Ch1 (2.5V) Full load start-up Ch1 (2.5V) Shutdown 2005 Semtech Corp. 24 SC2446A www.DataSheet4U.com Vin = 12V Io1 Vout1 = 2.5V Vin = 12V Vout1 = 2.5V www.semtech.com ...
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... POWER MANAGEMENT Typical Characteristics (Cont.) Ch2 (1.2V) Full load start-up Ch2 (1.2V) Shutdown 2005 Semtech Corp. 25 SC2446A www.DataSheet4U.com Vin = 12V Io2 Vout2 = 1.2V Vin = 12V Vout2 = 1.2V www.semtech.com ...
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... Typical Characteristics (Cont.) Vin = 12V, Dual output, Fsw = 500KHz, Tamb = Vin = 12V, Dual output, Fsw = 500KHz, Tamb = 2005 Semtech Corp. ° C, 0LFM 2.5V Output short and release. ° C, 0LFM 1.2V Output short and release. 26 SC2446A www.DataSheet4U.com www.semtech.com ...
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... AND - DETERMINED AT DATUM PLANE -H- DIMENSIONS DIM INCHES (.222 .161 .026 X .016 Y .061 Y Z .283 Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 27 SC2446A www.DataSheet4U.com DIMENSIONS INCHES MILLIMETERS NOM MAX MIN NOM MAX - - - - .047 1. .006 0.05 0.15 - .042 0.80 - 1.05 ...