LT3434 LINER [Linear Technology], LT3434 Datasheet
LT3434
Available stocks
Related parts for LT3434
LT3434 Summary of contents
Page 1
... The device also has a power good flag with a programmable threshold and time-out, and thermal shutdown protection. The LT3434 is available in a 16-pin TSSOP package with exposed pad leadframe for low thermal resistance. Supply Current vs Input Voltage ...
Page 2
... BOOST Pin Voltage ................................................. 68V SYNC PGFB, FB ................................................ 6V SS Operating JunctionTemperature Range LT3434EFE (Note 2) ........................ – 40°C to 125°C LT3434IFE (Note 2) ......................... – 40°C to 125°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are /SYNC = 0V unless otherwise noted ...
Page 3
... Note 4: Supply input current is the quiescent current drawn by the input pin. Its typical value depends on the voltage on the BIAS pin and operating state of the LT3434. With the BIAS pin at 0V, all of the quiescent current required to operate the LT3434 will be provided by the V BIAS voltage above its minimum input voltage, a portion of the total quiescent current will be supplied by the BIAS pin ...
Page 4
... LT3434 W U TYPICAL PERFOR A CE CHARACTERISTICS FB Voltage 1.30 1.29 1.28 1.27 1.26 1.25 1.24 1.23 1.22 1.21 1.20 –50 – 100 125 TEMPERATURE (°C) 3434 G01 SHDN Pin Current 5 25°C J 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1 SHDN VOLTAGE (V) 3434 G04 Bias Sleep Current 200 180 160 140 120 100 – ...
Page 5
... LOAD CURRENT = 0.5A 500 450 400 LOAD CURRENT = 1A 350 300 LOAD CURRENT = 2A 250 200 –50 –25 – 100 125 TEMPERATURE (°C) 3434 G22 LT3434 Oscillator Frequency vs FB Voltage 250 T = 25°C J 200 150 100 0.2 0.6 0.8 1.0 1.2 0.4 FB VOLTAGE (V) 3434 G12 Minimum Input Voltage 8 ...
Page 6
... LT3434 W U TYPICAL PERFOR A CE CHARACTERISTICS Burst Mode Operation V OUT 50mV/DIV I OUT 500mA/DIV V = 12V 5ms/DIV 3.3V OUT I = 100µ Load 2A Step Response V OUT 50mV/DIV I OUT 1A/DIV V = 12V 500µs/DIV 3.3V OUT C = 100µF OUT CTIO S NC (Pin 1): No Connection. ...
Page 7
... C high impedance when the clamp is active. The PG pin has a typical sink capability of 200µA. See the Power Good sits C section in Applications Information for details. LT3434 pin to ground C pin. See the Feedback section When PGFB ...
Page 8
... LC resonant fre- quency. This makes it much easier to frequency compen- sate the feedback loop and also gives much quicker tran- sient response. Most of the circuitry of the LT3434 operates from an internal 2.4V bias line. The bias regulator normally draws + CURRENT COMP – ...
Page 9
... U U APPLICATIO S I FOR ATIO FEEDBACK PIN FUNCTIONS The feedback (FB) pin on the LT3434 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 remaining part talks about frequency foldback and soft-start features ...
Page 10
... If opera- tion is required close to the minimum input required by the LT3434 a larger value may be required. This is to prevent excessive ripple causing dips below the minimum operat- ing voltage resulting in erratic operation. ...
Page 11
... To get low ESR takes volume, so physically smaller capacitors have higher ESR. The ESR range for typical LT3434 applications is 0.05Ω to 0.2Ω. A typical output capacitor is an AVX type TPS, 100µF at 10V, with a guaranteed ESR less than 0.1Ω. This is a “D” size surface mount solid tantalum capacitor ...
Page 12
... Application Note 19.) The LT3434 is able to maintain peak switch current limit over the full duty cycle range by using patented circuitry to 3434 F03 cancel the effects of slope compensation on peak switch current without affecting the frequency compensation it provides ...
Page 13
... 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 LT3434 switch, which has a minimum 3A limit. Higher values also reduce output ripple voltage and reduce core loss. ...
Page 14
... Short-Circuit Considerations The LT3434 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 as this peak current is reached ...
Page 15
... Figure 4. V dV/dt OUT Burst Mode OPERATION To enhance efficiency at light loads, the LT3434 automati- cally switches to Burst Mode operation which keeps the output capacitor charged to the proper voltage while minimizing the input quiescent current. During Burst Mode operation, the LT3434 delivers short bursts of ...
Page 16
... Low reverse leakage is critical to maximize low current efficiency since its value over tem- perature can potentially exceed the magnitude of the LT3434 supply current. Low forward drop is critical for high current efficiency since the loss is proportional to forward drop. These requirements result in the use of a Schottky type diode ...
Page 17
... SHUTDOWN FUNCTION AND UNDERVOLTAGE LOCKOUT The SHDN pin on the LT3434 controls the operation of the IC. When the voltage on the SHDN pin is below the 1.2V shutdown threshold the LT3434 is placed in a “zero” supply current state. Driving the SHDN pin above the shutdown threshold enables normal operation ...
Page 18
... SYNCHRONIZING Oscillator synchronization to an external input is achieved by connecting a TTL logic-compatible square wave with a duty cycle between 30% and 70% to the LT3434 SYNC pin. The synchronizing range is equal to initial operating frequency up to 700kHz. This means that minimum practical sync frequency is equal to the worst-case high self-oscillating frequency (230kHz), not the typical oper- ating frequency of 200kHz ...
Page 19
... C OUT PGFB 12k 100k V Disconnect 3.3V Logic Signal OUT OUT with 100µs Delay V = 3.3V LT3434 OUT 153k C OUT PGFB 12k 100k Figure 10. Power Good Circuits LT3434 > 4V with 100ms Delay V IN 200k PG 511k V = 3.3V OUT 200k 165k C OUT FB 100k C T 0.27µ 200k ...
Page 20
... This is the best thermal path for heat out of the package. Reducing the thermal resistance from Pin 8 and exposed pad onto the board will reduce die temperature and in- crease the power capability of the LT3434. This is achieved by providing as much copper area as possible around the exposed pad. Adding multiple solder filled feedthroughs under and around this pad to an internal ground plane will also help ...
Page 21
... V = Schottky diode forward drop switching frequency OSC A potential controllability problem arises if the LT3434 is called upon to produce an on time shorter than its typical value of 250ns. Feedback loop action will lower then reduce the V of cycle-skipping or Burst Mode behavior is exhibited. In summary aware that the simultaneous requirements of high ...
Page 22
... The LT3434 uses current mode control. This alleviates many of the phase shift problems associated with the inductor. The basic regulator loop is shown in Figure 12. The LT3434 can be considered as two g amplifier and the power stage. Figure 13 shows the overall loop response with a 470pF V capacitor and a typical 100µ ...
Page 23
... REF 0° – 8° 0.65 (.0256) BSC 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT MILLIMETERS (INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE LT3434 4.90 – 5.10* (.193 – .201) 3.58 (.141) 16 1514 6.40 2.94 (.252) ( ...
Page 24
... LT3434 RELATED PARTS PART NUMBER DESCRIPTION LT1074/LT1074HV 4. 100kHz, High Efficiency Step-Down DC/DC Converters OUT LT1076/LT1076HV 1. 100kHz, High Efficiency Step-Down DC/DC Converters OUT LT1676 60V, 440mA (I ), 100kHz, High Efficiency Step-Down DC/DC OUT Converter LT1765 25V, 2.75A (I ), 1.25MHz, High Efficiency Step-Down DC/DC OUT Converter LT1766 60V, 1. 200kHz, High Efficiency Step-Down DC/DC ...