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Document overview
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Technical content
Features
± 3.3V, 5V, 12V, and adjustable output versions (ADJ) ± Adjustable version output voltage range, 1.25V to 37V±2% max over line and load conditions ± Available in TO-220 and TO-263 packages ± Guaranteed 3A output load current ± Input voltage range up to 40V ± Requires only 4 external components ± Excellent line and load regulation specifications ± 150 kHz fixed frequency internal oscillator ± TTL shutdown capability ± Low power standby mode, IQ typically 80 µA ± G means Pb free in MSP1250G ± Uses readily available standard inductors ¸ Thermal shutdown a nd current limit protection
Applications
± Simple high-efficiency step-down (buck) regulator , CAR DVD electronic ± On-card switching regulators , LCD-TV , LCD-monitor , ADSL ± Positive to negative converter www.bookly.com 1
(BM2596H) 150kHz 3A Step-down Voltage Converter 5-Lead TO-220 (T) 5-Lead TO-263 (S) +VIN — This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be pres ent at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. Ground —Circuit ground . Output —Internal switch. The voltage at this pin switches between (+VIN - VSAT) and approximately -0.5V, with a duty cycle of approximately VOUT/VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be kept to a minimum. FeedBack —Senses the regulated output voltage to complete the feedback loop. —Allows the switching regulator c ircuit to be shut down using logic level s ignals thus dropping the total input supply current to approximately 80 µA. Pulling this pin below a threshold voltage of approximately 1.3V turns the regulator on, and pulling this pin above 1.3V (up to a maximum of 25V) shut s the regulator down. If this shutdown feature is not needed, the pin c an be wired to the ground pin or it c an be left open, in either case the regulator will be in the ON condition. Marking information: BM2596 -xx or BM2596H -xx on the chip, both two numbers are Pb-free; www.bookly.com 2 xx means output voltage 12 3 VIN VOUT GND FB
(BM2596H) 150kHz 3A Step-down Voltage Converter Block Diagram Absolute Maximum Ratings (Note 1) Parameter Rating Unit Maximum Supply Voltage 45 V Pin Input Voltage -0.3～25 V Feedback Pin Voltage -0.3～25 V Output Voltage to Ground (Steady State) -1 V Power Dissipation Internally limited -- Storage Temperature Range -65～150 Ċ ESD Susceptibility (Human Body Model) (Note 2) KV Maximum Junction Temperature 150 Ċ Temperature Range -40～125 ĊConditions Supply Voltage 4.5～40 V Note 1: Absolute Maximum Ratings indicate limi ts beyond which damage to the device may occur. Operating Ratings indicate c onditions for which the device is intended to be functional, but do not guarantee specific performance limits. Fo r guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin. www.bookly.com 3
(BM2596H) 150kHz 3A Step-down Voltage Converter Electrical CharacteristicsCondition :TJ = 25Ċ VO=3.3V BM2596H-- VO=3.3V Symbol Parameter Conditions Min (Note 4) Typ (Note 3) Max (Note4 ) Units SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 VOUT Output Voltage 4.75VVIN40V 0.2AILOAD3A 3.18 3.3 3.42 V ƿ Efficiency VIN=12VdILOAD=3A -- 75 -- % VO=5V BM2596H-- VO=5.0V Symbol Parameter Conditions Min (Note 4) Typ (Note 3) Max (Note4 ) Units SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 VOUT Output Voltage 7VVIN40V 0.2AILOAD3A 4.80 5.0 5.250 V ƿ Efficiency VIN=12Vd -- 84 -- % VO=12V BM2596H-- VO=12.0V Symbol Parameter Conditions Min (Note 4) Typ (Note 3) Max (Note4 ) Units SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 VOUT Output Voltage 15VVIN40V 0.2AILOAD3A 11.40 12.0 12.60 V ƿ Efficiency VIN=25VdILOAD=3A -- 88 --- % Vout is adjustable BM2596H—ADJ Symbol Parameter Conditions Min (Note 4) Typ (Note 3) Max (Note4 ) Units SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 VFB Feedback Voltage 4.5VVIN40V 0.2AILOAD3A VOUT programmed for 3V. Circuit of Figure 1 1.21 1.25 1.29 V ƿ Efficiency VIN=12Vd VOUT=3VdILOAD=3A -- 75 -- % www.bookly.com 4
(BM2596H) 150kHz 3A Step-down Voltage Converter All Output Voltage Versions Electrical Characteristics Condition :TJ = 25Ċ BM2596H—XX Symbol Parameter Conditions Min (Note 4) Typ (Note 3) Max (Note4 Units DEVICE PARAMETERS Ib Feedback Bias Current Adjustable Version Only, VFB = 1.3V -- 10 100 nA fO Oscillator Frequency (Note 6) 125 150 173 KHz VSAT VSAT Saturation Voltage IOUT=3A(Notes 7, 8) -- 1.16 1.5 V Max Duty Cycle DC Min Duty Cycle OFF (Note 9) -- 0 -- % ICL Current Limit Peak Current (Notes 7, 8) 4.2 4.8 5.5 A Output = 0V (Notes 7, 9) -- -- 50 DŽA IL Output Leakage Current Output =-1V (Notes 10) -- 2 30 mA IQ Quiescent Current (Note 9) -- 7 10 mA ISTBY Standby Quiescent Current ON/OFF pin = 5V (OFF) (Note 10) -- 80 250 DŽA ǀJC TO-220 or TO-263 Junction to Case -- 2 -- Ċ/W ǀJA TO-220 Package,Junction to Ambient(Note 11) -- 50 -- Ċ/W ǀJA Junction to Ambient (Note 12) -- 50 -- Ċ/W ǀJA TO-263 Package,Junction to Ambient(Note 13) -- 30 -- Ċ/W ǀJA Thermal Resistance Junction to Ambient(Note 14) -- 20 -- Ċ/W CONTROL Test Circuit Figure 1 ON /OFF Pin Logic Input -- 1.3 -- V VIH Low (Regulator on) -- -- 0.6 V VIL Threshold Voltage High(Regulator off) -- -- 2.0 V IH VLOGIC=2.5V (Regulator OFF) -- 5 15 DŽA IL ON /OFF Pin Input Current VLOGIC=0.5V (Regulator ON) -- 0.02 5 DŽA www.bookly.com 5
(BM2596H) 150kHz 3A Step-down Voltage Converter Note 3: Typical numbers are at 25Ċ and represent the most likely norm. Note 4: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temper ature limits are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits ar e used to calculate Average Outgoing Quality Level (AOQL). Note5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator system performance. Note 6: The switching frequency is reduced when the second stage current limit is activated. Note 7: No diode, inductor or capacitor connected to output pin. Note 8: Feedback pin removed from output and connecte d to 0V to force the output transistor switch ON. Note 9: Feedback pin removed from output and connected to 12V for the 3.3V, 5V, and the ADJ. version, and 15V for the 12V version, to force the output transistor switch OFF. Note 10: VIN = 40V. Note 11: Junction to ambient thermal resistance (no external heat sink) for the TO-220 package mounted vertically, with t he leads soldered to a printed circuit board with (1 oz.) copper area of approximately 1 in2. Note 12: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single printed circuit board with 0.5 in2 of (1 oz.) copper area. Note 13: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 2.5 in2 of (1 oz.) copper area. Note 14: Junction to ambient thermal resistance with the TO-263 package tab soldered to a double sided printed circuit board with 3 in 2 of (1 oz.) copper area on the MSP1250G side of the board, and approximately 16 in2 of copper on the other side of the p-c board. www.bookly.com 6
(BM2596H) 150kHz 3A Step-down Voltage Converter EXTERNAL COMPONENTS INPUT CAPACITOR C IN — A low ESR aluminum or tantal um bypass capacitor is needed between the input pin and ground pin. It must be located near the regulator using short leads. This capacitor prevents large voltage transients from appearing at the input, and provides the instantaneous current needed each time the switch turns on. Selecting an input capacitor requires consulting the manuf acturers data sheet for maximum allowable RMS ripple current. For a maximum ambient temperature of 40°C, a general guideline would be to select a capacitor with a ripple cu rrent rating of approximately 50% of the DC load current. For ambient temperatures up to 70°C, a current rating of 75% of the DC load current would be a good choice for a conservative design. The capacitor voltage rating must be at least 1.25 times greater than the maxi mum input voltage, and often a much higher voltage capacitor is needed to satisfy the RMS current requirements. FEEDFORWARD CAPACITOR (Adjustable Output Voltage Version) C FF ----A feed forward Capacitor C FF, shown across R2 in Figure1 is used when the output voltage is greater than 10V or when COUT has a very low ESR. This capacitor adds lead compensation to the feedback loop and increases the phase margin for better loop stability. OUTPUT CAPACITOR C OUT —An output capacitor is required to filter the output and provide regulator loop stability. Low impedance or low ESR Electrolytic or solid tantalum capacitors designed for switchi ng regulator applications mu st be used. When selecting an output capacitor, the im portant capacitor parameters are; the 100 kHz Equivalent Series resistance (ESR), the RMS ripple current rating, voltage rating, and capacitance value. For the output capacitor, the ESR va lue is the most important par ameter. The output capacitor requires an ESR value that has an upper and lower limit. For low output ripple voltage, a low ESR value is needed. This value is determi ned by the maximum allowable output ripple voltage, typically 1% to 2% of the output voltage. But if the selected capacitor’s ESR is extremely low, there is a possibility of an uns table feedback loop, resulting in an oscillation at the output. CATCH DIODE D ----Buck regulators require a diode to provide a return path for the inductor current when the swit ch turns off. This must be a fast diode and must be located close to the MSP1250G using shor t lea ds and short printed circui t traces. Because of their very fast switching speed and low forward voltage drop, Schottky diodes provide the best performance, especially in low output volt age applications (5V and lower). Ultra fast recovery, or High-Efficiency rectifiers are also a good choice, but some types with an abrupt turnoff characteristic may cause instability or EMI problems. INDUCTOR SELECTION L----All switching regulators have two basic modes of operation; continuous and discontinuous. The difference between the two types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for a period of time in the normal switching cycle. Each mode has distin ctively different operat ing characteristics, which can affect the regulators performance and requirements. Mo st switcher designs will operate in the discontinuous m ode when the load current is low. The MSP1250G (or any of the Simple Switcher family) can bemused fo r both continuous and di scontinuous modes of operation. www.bookly.com 7
(BM2596H) 150kHz 3A Step-down Voltage Converter Typical Application 1. Fixed Output Voltage Versions , BM2596 (BM2596H) 2. INVERTING REGULATOR The circuit in Figure following converts a posit ive input voltage to a negative output voltage with a common ground. The ci rcuit operates by bootstrapping the regulator’s ground pin to the negative output voltage, and then grounding the feedback pin, the MSP1250G generate a negative output voltage. Since this regulator topology can produce an output voltage that is either greater than or less than the input voltage, the maximum output current greatly depends on both the input and output voltage. The maximum voltage appearing across the regulator is the absolute sum of the input and output voltage, and this must be limited to a maximum of 40V.Additional diodes are required in this regulator configuration. Diode D1 is used to solate input voltage ripple or noise from coupling through the C IN capacitor to the output, under light or no load conditions. Wit hout diode D3, when the input voltage is first applied, the charging current of C IN can pull the output positive by several volts for a short period of time. Adding D3 prevents the output from going positive by more than a diode voltage. www.bookly.com 8
(BM2596H) 150kHz 3A Step-down Voltage Converter Test Circuit and Layout Guidelines CIN --470 DŽF, 50V, Aluminum Electrolytic Nichicon “PL Series” COUT --220 DŽF, 25V Aluminum Electrolytic, Nichicon “PL Series” D1--5A, 40V Schottky Rectifier, 1N5825 L1 --68DŽH, L38 where VREF = 1.23V Select R1 to be approximately 1 kc, use a 1% resistor for best stability. CIN --470 DŽF, 50V, Aluminum Electrolytic Nichicon “PL Series” COUT --220DŽF, 35V Aluminum Electrolytic, Nichicon “PL Series” D1--5A, 40V Schottky Rectifier, 1N5825 L1 --68 DŽH, L38 R1 --1 kc, 1% CFF --See Application Information Section www.bookly.com 9
wwwwww..bbooookkllyy..ccoomm 10 PACKAGE DIMENSION TO-220 (N220) R S J K N A C B D F G 1 23 T S C T J R B A F D G N K TO-263 (N263) A D C B I E L FG K