LTC1553L Linear Technology, LTC1553L Datasheet
LTC1553L
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LTC1553L Summary of contents
Page 1
... The LTC1553L uses a syn- chronous switching architecture with two external N-channel output devices, providing high efficiency and eliminating the need for a high power, high cost P-channel device ...
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... COMP = Open (Note INFORMATION TOP VIEW ORDER PART NUMBER OUTEN 3 VID0 18 LTC1553LCG 4 17 VID1 LTC1553LCSW 5 16 VID2 6 VID3 VID4 8 13 PWRGD 9 12 FAULT PACKAGE 20-LEAD PLASTIC SO = 125 C, = 100 125 C, = 100 C/ W (SW unless otherwise noted ...
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... Note 9: Under typical soft current limit, the net soft start discharge current will [–11 A(I SSIL current ratio is designed to be 5.5:1. Note 10: When VID0 to VID4 are all HIGH, the LTC1553L will be forced to shut down internally. The OUTEN trip voltages are guaranteed by design for all other input codes. LTC1553L MIN ...
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... LTC1553L W U TYPICAL PERFORMANCE CHARACTERISTICS Typical 2.8V V Distribution OUT 140 TOTAL SAMPLE SIZE = 1500 120 100 100 2.775 2.785 2.795 2.805 2.815 2.825 OUTPUT VOLTAGE (V) 1553L G01 Line Regulation 2.825 REFER TO TYPICAL APPLICATION 2.820 CIRCUIT FIGURE 1 OUTPUT = NO LOAD 2.815 ...
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... IMAX IFB SS CAP = 0.01 F 1.5 1.0 SHORT-CIRCUIT CURRENT 0 OUTPUT CURRENT (A) 1553L G17 LTC1553L Soft Start Source Current vs Temperature – 8 – 9 –10 –11 –12 –13 –14 –15 50 100 – 50 – TEMPERATURE ( C) 1553L G12 V Shutdown Supply Current CC vs Temperature ...
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... In hard current limit, the soft start capacitor will be forced low immedi- ately and the LTC1553L will rerun a complete soft start cycle. C must be selected such that during power-up the SS current through Q1 will not exceed the current limit value ...
Page 7
... OT trips. As OUTEN drops below 1.7V, the drivers are internally disabled to prevent the MOSFETs from heating further. If OUTEN is less than 1.2V for longer than 30 s, the LTC1553L will enter shutdown mode. The internal n oscillator can be synchronized to a faster external clock by applying the external clocking signal to the OUTEN pin. ...
Page 8
... G1 LTC1553L FAULT I MAX OT G2 COMP SS SGND GND SENSE NC Figure 12V + 0 RISE/FALL 5000pF LTC1553L G2 G2 RISE/FALL 5000pF GND Figure 1200 F 10k † Q1 15A V NC OUT MAX + †† ...
Page 9
... With external pull-up resistor † 1 Disabled (1.70) ** With respect to the output voltage selected in Table 3 as required by † 0 Disabled (1.75) Intel Specification VRM 8.2 † These code selections are disabled in LTC1553L X Don’t care LTC1553L INPUT PIN RATED OUTPUT VOLTAGE ( ID3 ID2 ID1 ...
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... OT will trip, issuing a warning to the external CPU. If the temperature continues to rise and the OUTEN input drops to 1.7V, the G1 and G2 pins will be forced low. If OUTEN is pulled below 1.2V, the LTC1553L will go into shutdown mode, cutting the supply current to a minimum. If thermal shutdown is not required, OUTEN can be con- nected to a conventional TTL enable signal ...
Page 11
... During start-up, the COMP pin is clamped to a diode drop above the voltage at the SS pin. This prevents the error amplifier, ERR, from forcing the loop to maxi- mum duty cycle. The LTC1553L will begin to operate at low duty cycle as the SS pin rises above about 1.2V (V 1.8V continues to rise amplifier begins to regulate the output ...
Page 12
... OUTEN pin. The synchronizing range extends from the initial operating frequency up to 500kHz. If the external frequency is much higher than the natural free-running frequency, the peak-to-peak sawtooth amplitude within the LTC1553L will decrease. Since the loop gain is in- . Their midpoint versely proportional to the amplitude of the sawtooth, the CC compensation network may need to be adjusted slightly ...
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... SO-8) or Siliconix SUD50N03 or Motorola MTD20N03HDL (both in D PAK) are small footprint sur- face mount devices with R of gate drive that work well in LTC1553L circuits. With higher output voltages, the R significantly lower than that for Q2. These conditions can often be met by paralleling two MOSFETs for Q1 and using a single device for Q2 ...
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... To minimize this effect, the inductor value should usually be in the range for most typical 5V input LTC1553L circuits. To optimize performance, different combinations of input and output voltages and expected loads may require different inductor values ...
Page 15
... ESR. During an output load transient, the output capacitor must supply all of the additional load current demanded by the load until the LTC1553L can adjust the inductor current to the new value. Output capacitor ESR results in a step in the output voltage equal to the ESR value multiplied by the change in load current ...
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... respectively. )(C1) C Figure 8b. Bode Plot of the LTC1553L Overall Transfer Function = f and Table 6. Suggested Compensation Network for 5V Input Application Using Multiple Paralleled 330 F AVX TPS Output Capacitors L ...
Page 17
... Once PWRGD goes low, the internal circuitry watches for the output voltage to exceed 115% of the rated voltage this happens, FAULT will be triggered. Once FAULT is triggered, G1 and G2 will be forced low immediately and the LTC1553L will remain in this state until V supply is recycled or OUTEN is toggled. 15% 5% RATED V OUT – ...
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... Do not connect these parts to the ground plane! 4. The V and PV decoupling capacitors should close to the LTC1553L as possible. The 10 F bypass ...
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... SYSTEM 5 5V 1.8k C1 DALE 150pF NTHS-1206N02 MOUNT THERMISTER IN CLOSE THERMAL PROXIMITY TO Q1 Figure 11. Single Supply LTC1553L 5V to 1.8V-3.5V Application with Thermal Monitor PACKAGE DESCRIPTION 0.205 – 0.212** (5.20 – 5.38) 0.005 – 0.009 0.022 – 0.037 (0.55 – 0.95) (0.13 – 0.22) * DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" ...
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... TYP COMMENTS Dual Version of LTC1148 Synchronous, V Synchronous, V Synchronous, V Synchronous N- or P-Channel FETs, Comparator/Low-Battery Detector Synchronous N-Channel FETs, Voltage Mode Drive Synchronous N-Channel, V Dual LTC1435 with Power-On Reset High Voltage Version of LTC1553L 0.394 – 0.419 (10.007 – 10.643 ...