LTC1147 Linear Technology, LTC1147 Datasheet
LTC1147
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LTC1147 Summary of contents
Page 1
... Constant off-time architecture provides low dropout regu- lation limited by only the R and resistance of the inductor and current sense resistor. The LTC1147 series incorporates automatic power saving Burst Mode operation to reduce switching losses when load currents drop below the level required for continuous operation ...
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... Shutdown LTC1147L Series Normal Mode Sleep Mode Shutdown (LTC1147L-3. Operating Ambient Temperature Range LTC1147C................................................ LTC1147I............................................. – Extended Commercial + 0.3V) to – 0.3V Temperature Range (Note 4) ................. – Junction Temperature (Note 1)............................ 125 C Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec) ...
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... C and 85 C. The D LTC1147I is guaranteed to meet the extended temperature limits )(150 C/W) Note 5: The LTC1147L/LTC1147L-3.3 allow operation Note 6: The LTC1147L is tested with external feedback resistors resulting in a nominal output voltage of 2.5V. LTC1147-3.3 LTC1147-5/LTC1147L = 0V, unless otherwise noted. SHDN MIN ...
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... LTC1147 • G07 4 Line Regulation 40 FIGURE 1 CIRCUIT LOAD –10 –20 –30 – INPUT VOLTAGE (V) Supply Current in Shutdown SHUTDOWN 18 (NOT AVAILABLE ON LTC1147L INPUT VOLTAGE (V) Off-Time vs V OUT 80 V SENSE 70 60 ...
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... Pin 6 high holds the P-channel MOSFET off and puts the LTC1147 in micropower shutdown mode. Requires CMOS logic signal with t On the LTC1147L this pin serves as the feedback pin from an external resistive divider used to set the output voltage. GND (Pin 7): Two independent ground lines must be routed separately to: 1) the (– ...
Page 6
... This causes the output of the gain stage U U APPLICATIO S I FOR ATIO LTC1147L Adjustable Applications When an output voltage other than 3. required, the LTC1147L adjustable version is used with an external resistive divider from (Pin 6) (see Figure 7). OUT FB The regulated voltage is determined by: ...
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... U U APPLICATIO S I FOR ATIO The basic LTC1147 application circuit is shown in Figure 1. External component selection is driven by the load requirement and begins with the selection known, C and L can be chosen. Next, the power SENSE T MOSFET and D1 are selected. Finally, C selected and the loop is compensated. The circuit shown in Figure 1 can be configured for operation input voltage of 16V ...
Page 8
... ESR requirements for the output capacitor are eased at the expense of efficiency. If too small an inductor is used, the inductor current will become discontinuous before the LTC1147 series enters Burst Mode operation. A consequence of this is that the LTC1147 series will delay entering Burst Mode operation and effi- ...
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... MOSFET (V IN < 4V) may be used expected to drop below 8V logic-level threshold MOSFET (V strongly recommended. When a logic-level MOSFET is used, the LTC1147 supply voltage must be less than the absolute maximum V ratings for the MOSFET. GS The maximum output current I determines the R MAX requirement for the power MOSFET ...
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... SENSE the voltage comparator. This causes Burst Mode opera- tion to be activated when the LTC1147 series would normally be in continuous operation. The effect is most pronounced with low values of R proved by operating at higher frequencies with lower values of L ...
Page 11
... The DC supply current is the current which flows into V (Pin 1) less the gate charge current. For V IN the LTC1147 series DC supply current is 160 A for no load, and increases proportionally with load constant 1.6mA after the LTC1147 series has entered continuous mode. Because the DC bias current is ...
Page 12
... The voltage on the C = 0.3 ground for periods of time as shown in Figure 6b. During this time the LTC1147 series are in sleep mode with the quiescent current reduced to 160 A. The inductor current should also be monitored. Look to verify that the peak-to-peak ripple current in continuous mode operation is approximately the same as in Burst Mode operation ...
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... Figure 7. Check the following in your layout: 1. Are the signal and power grounds segregated? The LTC1147 ground (Pin 7) must return separately to a) the power and b) signal grounds. The power ground (a) returns to the source anode of the Schottky diode and (–) plate of C ...
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... V IN 10V TO 14V + Si3455DV D1 MBRS130LT3 L* 220 100pF OUT 100 F 16V + R2 AVX R ** SENSE 6.8k 0.22 V OUT LTC1147 • F09 V IN 3.5V TO 12V + Si9433DY D1 16V MBRS130LT3 OUT 100 F 10V + AVX R ** SENSE 0.068 V OUT 3.3V/1.25A LTC1147 • F08 For Figure 9 ...
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... MIN 0.018 0.003 (0.457 0.076) LTC1147-3.3 LTC1147-5/LTC1147L V IN 3.5V TO 12V + Si9433DY 25V 2 MBRD330 49. OUT 220 F 10V AVX 49. SENSE 1% 0.05 2.5V/2A LTC1147 • F11 0.400* (10.160) MAX 0.255 0.015* (6.477 0.381) 0.020 (0.508 MIN 1197 15 ...
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... COMMENTS Dual Version of LTC1148 Dual Version of LTC1147 Nonsynchronous, 8-Lead, V 16V IN Synchronous, V 20V IN Synchronous, V 48V, for Standard Threshold FETs IN Synchronous, V 40V for Logic Level MOSFETS IN 0.5A Switch ...