LTC1149 Linear Technology Corporation, LTC1149 Datasheet
LTC1149
Available stocks
Related parts for LTC1149
LTC1149 Summary of contents
Page 1
... The operating current level is user-program- mable via an external current sense resistor. The LTC1149 series incorporates automatic power saving Burst Mode operation when load currents drop below the level required for continuous operation. Standby power is reduced to only about 8mW at V both MOSFETs are turned off ...
Page 2
... Extended Commercial Temperature Range ............................... – Junction Temperature (Note 1) ............................ 125 C Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec)................. 300 C ELECTRICAL C HARA TERISTICS C SYMBOL PARAMETER V Feedback Voltage (LTC1149 Only Feedback Current (LTC1149 Only Regulated Output Voltage OUT LTC1149-3.3 LTC1149-5 V Output Voltage Line Regulation ...
Page 3
... T Note dissipation P according to the following formulas: D LTC1149CN, LTC1149CN-3.3, LTC1149CN-5: T LTC1149CS, LTC1149CS-3.3, LTC1149CS-5: T Note 2: Pin shutdown pin on the LTC1149-3.3 and LTC1149-5 fixed output voltage versions and must be at ground potential for testing 12V CONDITIONS ...
Page 4
... INPUT VOLTAGE (V) Supply Current in Shutdown 400 SD2 300 200 100 INPUT VOLTAGE (V) Off-Time vs V OUT LTC1149-5 10 LTC1149-3 OUTPUT VOLTAGE (V) Load Regulation 20 FIGURE 1 CIRCUIT V = 24V IN 0 –20 –40 –60 –80 –100 50 0 0.5 1.0 1.5 LOAD CURRENT (A) 1149 G02 Operating Frequency vs (V – ...
Page 5
... Pin 7 voltage. – SENSE (Pin 8): Connects to internal resistive divider which sets the output voltage in LTC1149-3.3 and LTC1149-5 versions. Pin 8 is also the (–) input for the current comparator. + SENSE (Pin 9): The (+) Input for the Current Comparator. ...
Page 6
... To minimize the frequency variation as dropout is approached, the off- . When the timing time controller increases the discharge current as V drops below V MOSFET is turned on continuously. W Pin 10 connection shown for LTC1149-3.3 and LTC1149-5; changes create LTC1149. 500k – S ...
Page 7
... LTC1149 series and external is known, C SENSE T component values yields: are selected and the R SENSE A graph for selecting R current is given in Figure 2. The LTC1149 series works well with values of R The load current below which Burst Mode operation commences both track I SC(PK ...
Page 8
... ESR requirements for the output capacitor are T eased at the expense of efficiency. If too small an inductor is used, the inductor current will decrease past zero and change polarity. A consequence of this is that the LTC1149 is analogous to the series may not enter Burst Mode operation and efficiency will be severely degraded at low currents. ...
Page 9
... R = 0.007/ C can be used as an approximation for low voltage MOSFETs. C electrical characteristics. The constant K is much harder to pin down, but can be used for the LTC1149 series to estimate the relative contributions of the two terms in the P-channel dissipation equation. N-Channel MOSFET and D1 Selection < ...
Page 10
... DS(ON) The selection of C series resistance (ESR). The ESR Note DS(ON) than twice the value of R LTC1149 series: C Required ESR < 2R OUT Optimum efficiency is obtained by making the ESR equal the ESR is increased DS(ON) SENSE efficiency degrades by less than 1%. If the ESR is greater ...
Page 11
... APPLICATIO S I FOR ATIO output ripple at low frequencies will be large enough to trip the voltage comparator. This causes the Burst Mode operation to be activated when the LTC1149 series would normally be in continuous operation. The effect is most pronounced with low values of R improved by operating at higher frequencies with lower values of L ...
Page 12
... The DC supply current is the current which flows into V Pin 2 less the gate charge current. For V IN LTC1149 DC supply current is 0.6mA for no load, and increases proportionally with load up to 2mA after the LTC1149 series has entered continuous mode. Because the DC supply current is drawn from V resulting loss increases with input voltage ...
Page 13
... High input voltage applications in which large MOSFETs are being driven at high frequencies may cause the maxi- mum junction temperature rating for the LTC1149 series to be exceeded. The LTC1149 supply current is dominated by the gate charge supply current, which is given as a function of operating frequency in the Typical Perfor- mance Characteristics ...
Page 14
... R1, R2 must be connected between the (+) plate of C ground. 3. Are the SENSE minimum PC trace spacing? The differential decou- pling capacitor between Pins 8 and 9 should be as close as possible to the LTC1149 100 may be placed Pin 6 high to when the NGATE Pin 13 goes ...
Page 15
... Is the V decoupling capacitor connected closely CC between Pin 5 of the LTC1149 and power ground? This capacitor carries the MOSFET driver peak currents the SHDN1 Pin 10 (fixed output versions only) actively pulled to ground during normal operation? The SHDN1 pin is high impedance and must not be allowed to float ...
Page 16
... SHDN1 TH >2V = SHUTDOWN 8 9 – + SENSE SENSE 1000pF *COILTRONICS CTX02-11932 **DALE WSC-1/2-0 20V 1N4148 IRF9Z34 1 16 PGATE CAP SHDN2 RGND PDRIVE NGATE IRFZ34 LTC1149-3 PGND SGND SHDN1 SHUTDOWN – + SENSE SENSE 1000pF *COILTRONICS CTX33-4-KM **KRL SL-1-C1-0R033J + 100 F 35V SENSE 68 H 0.1 V OUT 3 ...
Page 17
... RGND PDRIVE NGATE Si9410DY LTC1149 PGND SGND SHDN1 SHUTDOWN – + SENSE SENSE 1000pF *DALE LPE-6562-220MB **KRL SL-1-C1-0R050J LTC1149 LTC1149-3.3/LTC1149-5 + 220 F 35V SENSE 33 H 0.05 V OUT 5V/2A + 220 F 10V 2 AVX 1N5818 1149 F12 + 100 F 25V SENSE 22 H 0.05 V OUT 5V/2A + 220 F 10V ...
Page 18
... SGND SHDN1 SHUTDOWN – + SENSE SENSE 1000pF *HURRICANE LAB HL-KI168M **IRC LR2512-01-R040 20V 1N4148 RFD15P05SM CAP 15 SHUTDOWN SHDN2 14 RGND 13 RFD14N05SM NGATE LTC1149 12 PGND 11 SGND R1A 100pF 10 33k – + SENSE 1000pF + 100 F 0.1 F 100V SENSE 68 H 0.04 V OUT 5V/2.5A + 220 F 10V OS-CON ...
Page 19
... Dimensions in inches (millimeters) unless otherwise noted. N Package 16-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.045 – 0.065 (1.143 – 1.651) 0.065 (1.651) TYP 0.018 0.003 0.100 0.010 (0.457 0.076) LTC1149 LTC1149-3.3/LTC1149-5 + 1000 F 220 63V 0.1 F 2N2222 MTP30N06EL L* R SENSE 50 H 0.02 ...
Page 20
... TYP V IN 20V TO 30V 1N4148 MTP23P06 100 H 16 PGATE CAP 15 V SHDN2 SHUTDOWN RGND CC 13 PDRIVE NGATE MTP36N06E LTC1149 12 V PGND SGND T 100pF 100 9 – + SENSE SENSE 1000pF 100 COMMENTS 4V < < V 3.5V < V 3.5V < ...