LT3430 Linear Technology, LT3430 Datasheet
LT3430
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LT3430 Summary of contents
Page 1
... A shutdown pin reduces supply current and a SYNC pin can be externally synchronized from 228kHz to 700kHz with a logic level input. The LT3430 is available in a thermally enhanced 16-pin TSSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. MMSD914TI ...
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... BOOST Pin Voltage ................................................. 68V SYNC Voltage ........................................................... 7V SHDN Voltage ........................................................... 6V BIAS Pin Voltage .................................................... 30V FB Pin Voltage/Current .................................. 3.5V/2mA Operating Junction Temperature Range LT3430EFE (Note 8) ......................... – 125 C LT3430IFE (Note 8) ......................... – 125 C Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec)................. 300 C ELECTRICAL CHARACTERISTICS The ...
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... C to 125 C junction temperature. Specifications over the – 125 C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3430IFE is guaranteed over the full – 125 C operating junction temperature range. Note 9: See Peak Switch Current Limit vs Junction Temperature graph in the Typical Performance Characteristics section ...
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... LT3430 W U TYPICAL PERFOR A CE CHARACTERISTICS Switch Peak Current Limit TYPICAL 4 GUARANTEED MINIMUM 100 DUTY CYCLE (%) 3430 G01 Lockout and Shutdown Thresholds 2.4 LOCKOUT 2.0 1.6 1.2 0.8 START-UP 0.4 SHUTDOWN 0 –50 – 100 125 JUNCTION TEMPERATURE ( C) 3430 G04 ...
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... SWITCH CURRENT (A) 3430 G14 Switch Peak Current Limit 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 –50 – 100 125 JUNCTION TEMPERATURE ( C) 3430 G16 LT3430 BOOST Pin Current SWITCH CURRENT (A) 3430 G12 Switch Minimum ON Time vs Temperature 600 500 400 ...
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... LT3430 CTIO S GND (Pins 16): The GND pin connections act as the reference for the regulated output, so load regulation will suffer if the “ground” end of the load is not at the same voltage as the GND pins of the IC. This condition will occur when load current or other currents flow through metal paths between the GND pins and the load ground ...
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... Most of the circuitry of the LT3430 operates from an internal 2.9V bias line. The bias regulator normally draws power from the regulator input pin, but if the BIAS pin is connected to an external voltage equal to or higher than 3V, bias power will be drawn from the external source (typically the regulated output voltage) ...
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... U W APPLICATIO S I FOR ATIO FEEDBACK PIN FUNCTIONS The feedback (FB) pin on the LT3430 is used to set output voltage and provide several overload protection features. The first part of this section deals with selecting resistors to set output voltage and the second part talks about foldback frequency and current limiting created by the FB pin ...
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... Lower values are chosen to reduce physical size of the inductor. Higher values allow more output current because they reduce peak current seen by the LT3430 switch, which has a 3A limit. Higher values also reduce output ripple voltage. When choosing an inductor you will need to consider output ripple voltage, maximum load current, peak induc- tor current and fault current in the inductor ...
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... Dead /L IN shorts will actually be more gentle on the inductor because the LT3430 has frequency and current limit foldback. Peak switch and inductor current can be significantly higher than output current, especially with smaller induc- Table 2 VENDOR/ PART NO ...
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... Maximum Output Load Current Maximum load current for a buck converter is limited by the maximum switch current rating (I for the LT3430 is 3A. Unlike most current mode convert- ers, the LT3430 maximum switch current limit does not fall off at high duty cycles. Most current mode converters suffer a drop off of peak switch current for duty cycles above 50% ...
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... LT3430 is designed to operate well in both modes of operation, allowing a large range of inductor values to be used. Short-Circuit Considerations The LT3430 is a current mode controller. It uses the V node voltage as an input to a current comparator which turns off the output switch on a cycle-by-cycle basis – ...
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... To get low ESR takes volume , so physically smaller capacitors have high ESR. The ESR range for typical LT3430 applications is 0. typical output capacitor is an AVX type TPS, 100 F at 10V, with a guaranteed ESR less than 0.1 . This is a “D” size surface mount solid tantalum capacitor ...
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... are suitable for most applications. If opera- tion is required close to the minimum input required by the output of the LT3430, a larger value may be required. This is to prevent excessive ripple causing dips below the minimum operating voltage resulting in erratic operation. ...
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... SHUTDOWN FUNCTION AND UNDERVOLTAGE LOCKOUT Figure 4 shows how to add undervoltage lockout (UVLO) to the LT3430. Typically, UVLO is used in situations where the input supply is current limited , or has a relatively high source resistance. A switching regulator draws constant power from the source, so source current increases as source voltage drops ...
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... R 116 387 LT3430 + 2.38V – 5 – 0.4V GND Figure 4. Undervoltage Lockout SYNCHRONIZING The SYNC input must pass from a logic level low, through the maximum synchronization threshold with a duty cycle can be FB between 10% and 90%. The input can be driven directly from a logic level output ...
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... When operating at higher currents and input volt- ages, with poor layout, this spike can generate voltages across the LT3430 that may exceed its absolute maximum rating. A ground plane should always be used under the switcher circuitry to prevent interplane coupling and over- all noise ...
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... Board layout also has a significant effect on thermal resistance. Pins and 16, GND, are a continuous copper plate that runs under the LT3430 die. This is an exposed pad and is the best thermal path for heat out of the package. Soldering the exposed pad to the copper ground plane under the device will reduce die temperature and increase the power capability of the LT3430 ...
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... U U APPLICATIO S I FOR ATIO THERMAL CALCULATIONS Power dissipation in the LT3430 chip comes from four sources: switch DC loss, switch AC loss, boost circuit current, and input quiescent current. The following formu- las show how to calculate each of these losses. These formulas assume continuous mode operation, so they should not be used for calculating efficiency at light load currents ...
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... APPLICATIO S I FOR ATIO calculation of the LT3430 die temperature more accurate die temperature is required, a measurement of the SYNC pin resistance (to GND) can be used. The SYNC pin resistance can be measured by forcing a voltage no greater than 0.5V at the pin and monitoring the pin current over temperature in an oven ...
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... U U APPLICATIO S I FOR ATIO Input Voltage vs Operating Frequency Considerations The absolute maximum input supply voltage for the LT3430 is specified at 60V. This is based solely on internal semi- conductor junction breakdown effects. Due to internal power dissipation, the actual maximum V a particular application may be less than this. ...
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... C CONVERTER WITH BACKUP OUTPUT REGULATOR In systems with a primary and backup supply, for ex- ample, a battery powered device with a wall adapter input, the output of the LT3430 can be held up by the backup ) can be F supply with the LT3430 input disconnected. In this condi- pin to ground ...
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... F 47k Figure 13. Buck Converter with Adjustable Soft-Start OUT – • • MMSD914TI 5V, 2A ALTERNATE SUPPLY R1 15. 100 F 4.99k 10V 3430 F12 OUTPUT 15.4k R2 4.99k C SS 15nF 3430 F13 L1: CDRH104R-220M LT3430 ms sn3430 3430is 23 ...
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... It differs from the standard approach in the way the IC chip derives its feedback signal because the LT3430 accepts only positive feedback sig- nals. The ground pin must be tied to the regulated negative output. A resistor divider to the FB pin then provides the proper feedback voltage for the chip ...
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... Minimum inductor continuous mode: † L1* MIN 36.5k For a 40V to –12V converter using the LT3430 with peak + C1 100 F switch current of 3A and a catch diode of 0.52V: 16V TANT R2 4.12k OUTPUT** –12V, 0.5A I CONT 3430 F15 For a load current of 0.5A, this says that discontinuous ...
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... LT3430 APPLICATIO S I FOR ATIO value equal to the peak-to-peak triangular waveform of the inductor. The low output ripple design in Figure 15 places the input capacitor between V and the regulated negative IN output. This placement of the input capacitor significantly reduces the size required for the output capacitor (versus ...
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... PAD DIMENSIONS, REFER TO TABLE 0.45 0.05 1.05 0.10 0.65 BSC 0 – 8 0.65 0.45 – 0.75 (.0256) BSC MILLIMETERS (INCHES) 4.90 – 5.10* (.193 – .201) 3.58 (.141) 16 1514 2.94 6.40 (.116) BSC 1.10 (.0433) MAX 0.05 – 0.15 (.002 – .006) 0.195 – 0.30 FE16 TSSOP 0802 (.0077 – .0118) LT3430 sn3430 3430is 27 ...
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... LT3430 RELATED PARTS PART NUMBER DESCRIPTION LT1074/LT1076 Step-Down Switching Regulators LT1082 1A High Voltage Efficiency Switching Voltage Regulator ® LTC 1149 High Efficiency Synchronous Step-Down Switching Regulator External FET Switches, V LT1176 Step-Down Switching Regulator LT1339 High Power Synchronous DC/DC Controller LT1370 High Efficiency DC/DC Converter ...