Datasheet LTC3894 (Analog Devices) - 8

LTC3894
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Shutdown (RUN) Threshold vs GATE Bias LDO (VIN - VCAP) Load GATE Bias LDO (VIN - VCAP) Temperature Regulation Dropout Regulation
1.300 0.00 7.00 VIN = 12V VIN = 7V 1.250 –0.60 6.88 1.200 –1.20 6.75 TION (%) TION (V) TAGE (V) 1.150 –1.80 6.63 ) REGULA ) REGULA 1.100 CAP CAP –2.40 6.50 RUN PIN VOL –V -V IN IN(V (V 1.050 –3.00 125°C 6.38 125°C RUN RISING 25°C 25°C RUN FALLING –55°C –55°C 1.000 –3.60 6.25 –75 –50 –25 0 25 50 75 100 125 150 0 4 8 12 16 20 0 4 8 12 16 20 TEMPERATURE (°C) IGATE (mA) IGATE (mA) 3894 G28 3894 G29 3894 G30
PIN FUNCTIONS GATE (Pin 1):
Gate Drive Output for External P-Channel and SENSE– pins across the sense resistor. For DCR sens- MOSFET. The voltage swing on this pin is between CAP ing, Kelvin connect SENSE+ and SENSE– pins across the and VIN. The GATE driver output is held low at VCAP to filter capacitor. When SENSE– is greater than 3.2V, the turn on the P-channel MOSFET and held high at VIN to SENSE– pin supplies power to internal circuitry. To reduce turn off the MOSFET. The gate driver output is held high sensing errors, minimize the impedance in series with the when (VIN-VCAP) is less than VUVLO. SENSE– pin.
RUN (Pin 3):
Run Control High Impedance Input. A RUN
ITH (Pin 7):
Error Amplifier Output and Switching voltage above the 1.26V threshold enables normal opera- Regulator Compensation Point. The voltage on this pin tion, while forcing this pin below 1.12V shuts down the sets the current sense threshold. controller. Forcing this pin below 0.7V shuts down the
PGUV (Pin 8):
Pgood Undervoltage (UV) Comparator entire LTC3894, reducing quiescent current to approxi- High Impedance Input. Connect the PGUV pin to the out- mately 7µA. This pin can be tied to VIN directly or pulled put through a resistor feedback divider or connect directly up by a resistor. Do not float this pin. to VFB pin to program the output PGOOD UV threshold.
SENSE+ (Pin 5):
Differential Current Sensing (+) Input. When the PGUV pin voltage falls below 0.72V (0.8V – 10%) For RSENSE current sensing, Kelvin (4-wire) connect or lower, the PGOOD pin is asserted low after a 100µs SENSE+ and SENSE– pins across the sense resistor. For blanking period. DCR sensing, Kelvin connect SENSE+ and SENSE– pins
V
across the sense filter capacitor.
FB (Pin 9):
Output Feedback Sense Input. A resistor divider from the output to this pin sets the regulated out-
SENSE– (Pin 6):
Differential Current Sensing (–) Input. For put voltage. The LTC3894 will nominally regulate VFB to RSENSE current sensing, Kelvin (4-wire) connect SENSE+ the internal reference value of 0.8V. Rev. A 8 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Electrical Characteristics Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts