LTC1909-8 LINER [Linear Technology], LTC1909-8 Datasheet
LTC1909-8
Available stocks
Related parts for LTC1909-8
LTC1909-8 Summary of contents
Page 1
... Fault protection is provided by internal foldback current limiting, an output overvoltage comparator and optional short-circuit shutdown timer. The LTC1909-8 is available in the 28-lead SSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation trademark of Linear Technology Corporation. ...
Page 2
... TG, BG, INTV , EXTV RMS Currents .............. 50mA CC CC Operating Ambient Temperature Range LTC1909-8EG (Note 2) ....................... – Junction Temperature (Note 4) ............................ 125 C Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS over the full operating temperature range, otherwise specifications are T ...
Page 3
... 5mA PGOOD 5.5V (Note 5) unless otherwise stated. CC CONDITIONS CPUON, PGTMR Pins Are Open V Programmed from 1.3V to 3.5V OSENSE SDA Not Acknowledging PIN V = 5.5V for VRON only PIN LTC1909-8 denotes specifications which apply = 15V unless otherwise noted. IN MIN TYP MAX 520 600 680 0.8 1.5 4 4.5 3.5 4.2 – 0.5 – ...
Page 4
... Specifications over the – operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: The LTC1909-8 is tested in a feedback loop that adjusts V achieve a specified error amplifier output voltage (I Note calculated from the ambient temperature T ...
Page 5
... G20 Current Sense Threshold vs I Voltage TH 300 RNG 1.4V 200 1V 0.7V 100 0.5V 0 –100 –200 0 1.0 1.5 2.0 2.5 0.5 I VOLTAGE (V) TH 19098 G23 LTC1909-8 Efficiency vs Load Current 100 DISCONTINUOUS 90 MODE 80 CONTINUOUS MODE 10V 2.5V OUT EXTV = 5V CC FIGURE 1 CIRCUIT 50 0.001 0.01 0.1 1 LOAD CURRENT (A) Load Regulation ...
Page 6
... LTC1909 TYPICAL PERFOR A CE CHARACTERISTICS Maximum Current Sense Threshold vs V Voltage RNG 300 250 200 150 100 50 0 0.5 0.75 1.0 1.25 1.5 1.75 2.0 V VOLTAGE (V) RNG 19098 G25 Error Amplifier g vs Temperature m 2.0 1.8 1.6 1.4 1.2 1.0 50 125 –50 – 100 TEMPERATURE ( C) 19098 G28 RUN/SS Pin Current vs Temperature 3 2 PULL-DOWN CURRENT ...
Page 7
... G05 SDA, CPUON, PGTMR Output Low Voltage vs Temperature 0. 3mA PIN V = 2.7V 0.20 CC 0.15 0. 5.5V CC 0.05 0 – 55 –35 – 105 125 TEMPERATURE ( C) 19098 G08 LTC1909-8 Resistance Between V and OSENSE FB Pins vs Temperature 20. 2.7V TO 5.5V CC 20.06 20.04 20.02 20.00 19.98 19.96 19.94 19.92 19.90 19.88 – 55 –35 – 105 125 TEMPERATURE ( C) 19098 G03 ...
Page 8
... LTC1909 TYPICAL PERFOR A CE CHARACTERISTICS SDA, PGTMR, CPUON Sink Current vs Temperature 5.5V SK2 2.7V SK1 – 55 –35 – 105 125 TEMPERATURE ( C) 19098 G10 VRON Pull-Up Current vs Supply Voltage 3 RON 2.5 2.0 1.5 1.0 0.5 0 1.5 2.5 3.5 4.5 5.5 6.5 SUPPLY VOLTAGE (V) ...
Page 9
... VRON (Pin 13): Global Control Input. This TTL compatible input pin is pulled up internally by a 2.5 A current source. Pulling VRON low forces the open-drain output pins (CPUON and PGTMR) to pull to ground. If the LTC1909-8 is programmed to turn on a DC/DC converter, pulling VRON high three-states the CPUON pin and allows the switching regulator to soft-start if CPUON is tied to the RUN/SS pin ...
Page 10
... LTC1909 CTIO S FB (Pin 17): Feedback Input. Center tap of the SMBus programmable divider that is connected to Pin 9. GND (Pin 18): SMBus Programmer Ground. Connect to regulator signal ground at Pin 7. V (Pin 19): Positive Supply of the SMBus VID Program- CC mer. 2.7V V 5.5V. May be connected to the INTV CC pin. Bypass this pin to ground with a 0.1 F ceramic capacitor if using an external supply ...
Page 11
... A 0.8V – FCNT ON SWITCH LOGIC SHDN – – RUN SS SHDN – RUN/SS 0.6V C *PART OF THE SMBus VID PROGRAMMER LTC1909 0.8V REF 5V REG BOOST SENSE INTV OSENSE ...
Page 12
... LTC1909 DIAGRA S 12 ACK DCON VID0 VID1 VID2 VID3 VID4 ACK ACK DCON VID0 VID0 VID1 VID1 VID2 VID2 VID3 VID4 VID3 VID4 ACK ACK R/W VID0 VID1 VID2 VID3 VID4 ACK ACK ACK ACK R/W R/W 19098f ...
Page 13
... PH SPL t t PGL PGL t SSL 90% 10% NOTE: TIMING RELATIVE TO THE STOP BIT (P) IS MEASURED FROM THE RISING EDGE OF SDA SEE TABLE 1 FOR V AND V SENSE VOLTAGES MIN MAX LTC1909-8 t HD:STA t SU:STO 19098 TD02 START STOP P 2nd OFF PROTOCOL PPL ...
Page 14
... LTC1909-8 U OPERATIO (Refer to Functional Diagram) The LTC1909-8 consists of two independent sections: a current mode controller for the DC/DC step-down con- verter and a SMBus VID voltage programmer. It simplifies the design of SMBus controlled power supplies. Current Mode Controller In normal operation, the top MOSFET of the current mode controller is turned on for a fixed interval determined by a one-shot timer OST ...
Page 15
... DC/DC converters are operating and latching in VID codes only in Setup protocols. After power-up, the microprocessor must set up the reg- isters before the LTC1909-8 recognizes On protocols. This requirement ensures that the correct DC/DC converter out- put is programmed before the converters are turned on. After setup, Read-Back allows the contents of Registers 0 and verified in case the VID codes were corrupted by noise or bus conflicts ...
Page 16
... Registers 0 and 1 are protected and can only be altered with Setup protocols if VRON is pulled low or two Off protocols are sent to the LTC1909-8 (to force SMBON low). During Read-Back, the microproces- sor can check the On or Off state of the controller by testing the DCON status bit that follows each 5-bit code ...
Page 17
... The maximum allowed sense is selected for IN voltage is about 1.33 times this nominal value. Connecting the SENSE The LTC1909-8 can be used with or without a sense Pin resistor. When using a sense resistor placed between the source of the bottom MOSFET M2 and ground. Con- nect the SENSE so that the resistor appears between the SENSE PGND pins ...
Page 18
... JUNCTION TEMPERATURE ( C) Figure 2. R vs. Temperature DS(ON The power dissipated by the top and bottom MOSFETs strongly depends upon their respective duty cycles and the load current. When the LTC1909-8 is operating in continuous mode, the duty cycles for the MOSFETs are: D TOP , (BR)DSS D BOT , reverse DS(ON) ...
Page 19
... LTC1909 OUT OUT The largest ripple current OUT(MAX guarantee that ripple current OUT OUT MAX ( ) IN MAX ( ) ® cores. A variety of inductors designed for high VON VON2 0.01 F 10k LTC1909 19098 F03 (3b) 19098f 19 ...
Page 20
... LTC1909 APPLICATIO S I FOR ATIO Schottky Diode D1 Selection The Schottky diode D1 shown in Figure 1 conducts during the dead time between the conduction of the power MOSFET switches intended to prevent the body diode of the bottom MOSFET from turning on and storing charge during the dead time, which can cause a modest (about 1%) efficiency loss ...
Page 21
... Minimum Off-time and Dropout Operation The minimum off-time t time that the LTC1909-8 is capable of turning on the bottom MOSFET, tripping the current comparator and turning the MOSFET back off. This time is generally about 300ns. The minimum off-time limit imposes a maximum ...
Page 22
... GATECHG 10 TG Soft-Start and Latchoff with the RUN/SS Pin The RUN/SS pin provides a means to shut down the LTC1909-8 as well as a timer for soft-start and overcurrent latchoff. Pulling the RUN/SS pin below 0.8V puts the LTC1909-8 into a low quiescent current shutdown CC (I < 30 A). Releasing the pin allows an internal 1.2 A ...
Page 23
... C produce the most improvement. Although all dissipative SS elements in the circuit produce losses, four main sources 19098 F06 account for most of the losses in LTC1909-8 circuits: (6d losses. These arise from the resistances of the MOSFETs, inductor and PC board traces and cause the efficiency to drop at high output currents ...
Page 24
... LTC1909 APPLICATIO S I FOR ATIO sufficient capacitance to prevent the RMS current from causing additional upstream losses in fuses or batteries. Other losses, including C ESR loss, Schottky diode D1 OUT conduction loss during dead time and inductor core loss generally account for less than 2% additional loss. When making adjustments to improve efficiency, the input cur- rent is the best indicator of changes in efficiency ...
Page 25
... V EXTV SEL SDA GND 12 17 SCL FB C2 6.8nF 13 16 VRON V OSENSE 14 15 PGTMR CPUON LTC1909 025 . 125 ( ) 50V 3 M1 IRF7811A 270 F IRF7811A UPS840 2V 2 19098 F07 C : UNITED CHEMICON THCR70EIH226ZT ...
Page 26
... First, the 7-bit slave ad- dress for both protocols is internally hardwired to 1110 001B = E2H. A single R/W bit follows the slave address. This bit is low for data transfer from the microprocessor to the LTC1909-8 and high for transfers in the opposite direction ...
Page 27
... SDA GND 12 17 SCL VRON V OSENSE 14 15 PGTMR CPUON V OUT 100mV/DIV 1.5V I 10A/DIV 3711 F09 Figure 10. Transient Response with Active Voltage Positioning LTC1909 50V 3 M1 IRF7811A IRF7811A B540 2 R SENSE 0.003 19098 F08 C : UNITED CHEMICON THCR70EIH226ZT CORNELL DUBILIER ...
Page 28
... SDA transitions respectively, while SCL is high. In between the start and stop bits, the microproces- sor transmits four bytes to the LTC1909-8. These are the address byte, an 8-bit command code and two data bytes. The LTC1909-8 samples each bit at the rising edges of the SCL clock ...
Page 29
... High byte). As defined in the SMBus specifications, the microprocessor does not acknowledge the last data byte. The LTC1909-8 enters an idle state to wait for the next start bit after clocking out the Data High byte. The five most significant bits (VID0-VID4) of the Data Low and High bytes are the resistor divider settings previously loaded using the Setup protocol ...
Page 30
... IN OUT compact area. It may help to have some components on the bottom side of the board. • Place LTC1909-8 chip with Pins facing the power components. Keep the components connected to Pins close to LTC1909-8 (noise sensitive components). • Use an immediate via to connect the components to ground plane including SGND, GND and PGND of LTC1909-8 ...
Page 31
... SDA GND 12 17 SCL VRON V OSENSE 14 15 PGTMR CPUON Figure 12. LTC1909-8 PCB Layout Diagram U G Package 28-Lead Plastic SSOP (5.3mm) (Reference LTC DWG # 05-08-1640) 1.25 0. 5.3 – 5.7 0.65 BSC – 8 0.65 0.55 – 0.95 (.0256) (.022 – .037) BSC 0.22 – ...
Page 32
... LTC1909-8 RELATED PARTS PART NUMBER DESCRIPTION LTC1380/LTC1393 Multiplexer with SMBus Interface LTC1622 550kHz Step-Down Controller LTC1623 SMBus Dual High Side Switch Controller LTC1625/LTC1775 No R Current Mode Synchronous Step-Down Controller SENSE LTC1628-SYNC Dual, 2-Phase Synchronous Step-Down Controller LTC1694/LTC1694-1 SMBus Accelerator LTC1699-80 SMBus VID Programmer Compliant with Intel ...