LT3430EFE-1 LINER [Linear Technology], LT3430EFE-1 Datasheet

Page 1

FEATURES Wide Input Range: 5.5V to 60V ■ ■ 3A Peak Switch Current over All Duty Cycles Constant Switching Frequency: ■ 200kHz (LT3430) 100kHz (LT3430-1) 0.1Ω Switch Resistance ■ Current Mode ■ ■ Effective Supply Current: 2.5mA Shutdown Current: 30µA ...

Page 2

... T EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB ORDER PART NUMBER LT3430EFE LT3430IFE LT3430EFE-1 LT3430IFE-1 Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. ...

Page 3

... See Typical Performance Characteristics for the graph of switch voltage at other currents. Note 8: The LT3430EFE/LT3430EFE-1 are guaranteed to meet performance specifi cations from 0°C to 125°C junction temperature. Specifi cations over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3430IFE/LT3430IFE-1 are guaranteed over the full – ...

Page 4

LT3430/LT3430-1 TYPICAL PERFORMANCE CHARACTERISTICS Switch Peak Current Limit 25° TYPICAL 4 GUARANTEED MINIMUM DUTY CYCLE (%) 3430 G01 Lockout and Shutdown Threshold 2.4 LOCKOUT 2.0 1.6 1.2 0.8 ...

Page 5

TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequency 230 (LT3430) 220 210 200 190 180 170 –50 – 100 JUNCTION TEMPERATURE (°C) 3430 G10 V Pin Shutdown Threshold C 2.1 1.9 1.7 1.5 1.3 1.1 0.9 0.7 –50 –25 ...

Page 6

LT3430/LT3430-1 PIN FUNCTIONS GND (Pins 16, 17): 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 ...

Page 7

BLOCK DIAGRAM The LT3430/LT3430-1 are constant frequency, current mode buck converters. This means that there is an in- ternal clock and two feedback loops that control the duty cycle of the power switch. In addition to the normal error amplifi ...

Page 8

LT3430/LT3430-1 APPLICATIONS INFORMATION FEEDBACK PIN FUNCTIONS The feedback (FB) pin on the LT3430/LT3430-1 is used to set output voltage and provide several overload protection features. The fi rst part of this section deals with selecting resistors to set output voltage ...

Page 9

APPLICATIONS INFORMATION LT3430 AMPLIFIER Q2 V GND C tion should be used if resistors are increased beyond the suggested values and short-circuit conditions occur with high input voltage. High frequency pickup will increase and the protection accorded by frequency and ...

Page 10

LT3430/LT3430-1 APPLICATIONS INFORMATION inductor value to achieve a desirable output ripple volt- age level. If output ripple voltage is of less importance, the subsequent suggestions in Peak Inductor and Fault Current and EMI will additionally help in the selection of ...

Page 11

APPLICATIONS INFORMATION Peak switch and inductor current can be signifi cantly higher than output current, especially with smaller inductors and lighter loads, so don’t omit this step. Powdered iron cores are forgiving because they saturate softly, whereas ferrite cores saturate ...

Page 12

LT3430/LT3430-1 APPLICATIONS INFORMATION Reduced Inductor Value and Discontinuous Mode If the smallest inductor value is of most importance to a converter design, in order to reduce inductor size/cost, discontinuous mode may yield the smallest inductor solu- tion. The maximum output ...

Page 13

APPLICATIONS INFORMATION where switching frequency t = switch minimum on time diode forward voltage Input voltage IN I • inductor I • R voltage drop If this condition is not ...

Page 14

LT3430/LT3430-1 APPLICATIONS INFORMATION frequency gain of the error amplifi er, including the gain at the switching frequency. If the gain of the error amplifi high enough at the switching frequency, output ripple voltage (although smaller for a ceramic ...

Page 15

APPLICATIONS INFORMATION poor RFI behavior and if the overshoot is severe enough, damage the IC itself. The suggested catch diode (D1 International Recti- fi er 30BQ060 Schottky rated at 3A average forward current and 60V reverse ...

Page 16

LT3430/LT3430-1 APPLICATIONS INFORMATION INPUT − ∆ OUT = − µ ...

Page 17

APPLICATIONS INFORMATION LAYOUT CONSIDERATIONS As with all high frequency switchers, when considering layout, care must be taken in order to achieve optimal electrical, thermal and noise performance. For maximum effi ciency, switch rise and fall times are typically in the ...

Page 18

LT3430/LT3430-1 APPLICATIONS INFORMATION The V and FB components should be kept as far away as C possible from the switch and boost nodes. The LT3430/ LT3430-1 pinout has been designed to aid in this. The ground for these components should ...

Page 19

APPLICATIONS INFORMATION THERMAL CALCULATIONS Power dissipation in the LT3430/LT3430-1 chip comes from four sources: switch DC loss, switch AC loss, boost circuit current, and input quiescent current. The follow- ing formulas show how to calculate each of these losses. These ...

Page 20

LT3430/LT3430-1 APPLICATIONS INFORMATION lower V may generate greater losses due to switch DC IN losses. In general, the maximum and minimum V should be checked with maximum typical load current for calculation of the LT3430/LT3430-1 die temperature more ...

Page 21

APPLICATIONS INFORMATION ings = 0.233W • 45°C/W = 11°C. The 7V zener should be sized for excess of 0.233W operaton. The tolerances of the zener should be considered to ensure minimum V exceeds 3. DROOP Input Voltage ...

Page 22

LT3430/LT3430-1 APPLICATIONS INFORMATION stability. This ESR, however, contributes signifi cantly to the ripple voltage at the output (see Output Ripple Voltage in the Applications Information section possible to reduce capacitor size and output ripple voltage by replac- ing ...

Page 23

APPLICATIONS INFORMATION LT3430/LT3430-1 will consume their quiescent operating current of 1.5mA. The V pin will also source current to IN any other components connected to the input line. If this load is greater than 10mA or the input could be ...

Page 24

LT3430/LT3430-1 APPLICATIONS INFORMATION DUAL OUTPUT SEPIC CONVERTER The circuit in Figure 14 generates both positive and negative 5V outputs with a single piece of magnetics. The two induc- tors shown are actually just two windings on a standard Coiltronics inductor. ...

Page 25

APPLICATIONS INFORMATION D2 MMSD914TI C2 0.68µF INPUT BOOST 5. 44V LT3430 FB GND 4.7µF 30BQ060 100V C C CER INCREASE L1 FOR HIGHER CURRENT APPLICATIONS. SEE ...

Page 26

LT3430/LT3430-1 APPLICATIONS INFORMATION 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 signifi ...

Page 27

PACKAGE DESCRIPTION 6.60 ±0.10 4.50 ±0.10 SEE NOTE 4 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) (.020 – .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT ...

Page 28

LT3430/LT3430-1 RELATED PARTS PART NUMBER DESCRIPTION LT1074/LT1074HV 4. 100kHz, High Effi ciency Step-Down DC/DC OUT Converters LT1076/LT1076HV 1. 100kHz, High Effi ciency Step-Down DC/DC OUT Converters LT1676 60V, 440mA (I ), 100kHz, High Effi ciency Step-Down ...