Datasheet LTC3875 (Analog Devices) - 9
| Manufacturer | Analog Devices |
| Description | Dual, 2-Phase, Synchronous Controller with Low Value DCR Sensing and Temperature Compensation |
| Pages / Page | 46 / 9 — PIN FUNCTIONS TK/SS1, TK/SS2 (Pin 1, Pin 8):. ENTMPB (Pin 18):. PGOOD … |
| File Format / Size | PDF / 997 Kb |
| Document Language | English |
PIN FUNCTIONS TK/SS1, TK/SS2 (Pin 1, Pin 8):. ENTMPB (Pin 18):. PGOOD (Pin 19):. EXTV. CC (Pin 24):
Model Line for this Datasheet
Text Version of Document
LTC3875
PIN FUNCTIONS TK/SS1, TK/SS2 (Pin 1, Pin 8):
Output Voltage Tracking
ENTMPB (Pin 18):
Enable Pin for Temperature Balanc- and Soft-Start Inputs. When one channel is configured to ing Function. Ground this pin to enable the temperature be the master, a capacitor to ground at this pin sets the balancing function. Float this pin for normal operation. ramp rate for the master channel’s output voltage. When
PGOOD (Pin 19):
Power Good Indicator Output. Open-drain the channel is configured to be the slave, the feedback logic that is pulled to ground when either channel’s output voltage of the master channel is reproduced by a resistor exceeds ±7.5% regulation window, after the internal 20µs divider and applied to this pin. Internal soft-start currents power bad mask timer expires. of 1.25µA charge these pins.
EXTV V + + CC (Pin 24):
External Power Input to an Internal Switch
OSNS1 , VOSNS2 (Pin 2, Pin 6):
Positive Inputs of Remote Connected to INTV Sensing Differential Amplifiers. These pins receive the CC. This switch closes and supplies the IC power, bypassing the internal low dropout regulator, remotely sensed feedback voltage from external resistive whenever EXTV divider across the output. The differential amplifier out- CC is higher than 4.7V. Do not exceed 6V on this pin and make sure that EXTV puts are connected directly to the error amplifiers’ inputs CC < VIN at all times. internally inside the IC.
INTVCC (Pin 25):
Internal 5.5V Regulator Output. The con- trol circuits are powered from this voltage. Decouple this
V – – OSNS1 , VOSNS2 (Pin 3, Pin 7):
Negative Inputs of Re- pin to PGND with a minimum of 4.7µF low ESR tantalum mote Sensing Differential Amplifiers. Connect these pins or ceramic capacitor. to the negative terminal of the output capacitors when remote sensing is desired. Connect these pins to local
VIN (Pin 26):
Main Input Supply. Decouple this pin to signal ground if remote sensing is not used. PGND with a capacitor (0.1µF to 1µF).
ITH1, ITH2 (Pin 4, Pin 5):
Current Control Threshold and
BG1, BG2 (Pin 27, Pin 23):
Bottom Gate Driver Outputs. Error Amplifier Compensation Points. The current com- These pins drive the gates of the bottom N-channel parators’ tripping thresholds increase with these control MOSFETs between INTVCC and PGND. voltages.
BOOST1, BOOST2 (Pin 28, Pin 22):
Boosted Floating
TAVG (Pin 13):
Average Temperature Summing Point. Con- Driver Supplies. The (+) terminal of the booststrap capaci- nect a resistor to ground to sum all currents together for tors connect to these pins. These pins swing from a diode multi-channels or multi-IC operations when temperature voltage drop below INTVCC up to VIN + INTVCC. balancing function is enabled. The value of the resistor
TG1, TG2 (Pin 29, Pin 21):
Top Gate Driver Outputs. These should be the TRSET resistor value divided by the number are the outputs of floating drivers with a voltage swing of channels in the system. Float this pin if thermal balanc- equal to INTV ing is not used. CC superimposed on the switch node voltage.
SW1, SW2 (Pin 30, Pin 20):
Switch Node Connections to
FREQ (Pin 15):
There is a precision 10µA current flowing Inductors. Voltage swing at these pins is from a Schottky out of this pin. A resistor to ground sets a voltage which diode (external) voltage drop below ground to V in turn programs the frequency. Alternatively, this pin can IN. be driven with a DC voltage to vary the frequency of the
CLKOUT (Pin 31):
Clock Output Pin. Clock output with internal oscillator. phase changeable by PHASMD to enable usage of multiple LTC3875s in multiphase systems signal swing is from
IFAST (Pin 17):
Programmable Pin for Fast Transient Op- INTV eration for Channel 2 Only. A resistor to ground programs CC to ground. the threshold of the output load transient excursion. Float this pin to disable this function. See the Applications Information section for more details. 3875fb For more information www.linear.com/LTC3875 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Related Parts
PIN FUNCTIONS TK/SS1, TK/SS2 (Pin 1, Pin 8):
Output Voltage Tracking
ENTMPB (Pin 18):
Enable Pin for Temperature Balanc- and Soft-Start Inputs. When one channel is configured to ing Function. Ground this pin to enable the temperature be the master, a capacitor to ground at this pin sets the balancing function. Float this pin for normal operation. ramp rate for the master channel’s output voltage. When
PGOOD (Pin 19):
Power Good Indicator Output. Open-drain the channel is configured to be the slave, the feedback logic that is pulled to ground when either channel’s output voltage of the master channel is reproduced by a resistor exceeds ±7.5% regulation window, after the internal 20µs divider and applied to this pin. Internal soft-start currents power bad mask timer expires. of 1.25µA charge these pins.
EXTV V + + CC (Pin 24):
External Power Input to an Internal Switch
OSNS1 , VOSNS2 (Pin 2, Pin 6):
Positive Inputs of Remote Connected to INTV Sensing Differential Amplifiers. These pins receive the CC. This switch closes and supplies the IC power, bypassing the internal low dropout regulator, remotely sensed feedback voltage from external resistive whenever EXTV divider across the output. The differential amplifier out- CC is higher than 4.7V. Do not exceed 6V on this pin and make sure that EXTV puts are connected directly to the error amplifiers’ inputs CC < VIN at all times. internally inside the IC.
INTVCC (Pin 25):
Internal 5.5V Regulator Output. The con- trol circuits are powered from this voltage. Decouple this
V – – OSNS1 , VOSNS2 (Pin 3, Pin 7):
Negative Inputs of Re- pin to PGND with a minimum of 4.7µF low ESR tantalum mote Sensing Differential Amplifiers. Connect these pins or ceramic capacitor. to the negative terminal of the output capacitors when remote sensing is desired. Connect these pins to local
VIN (Pin 26):
Main Input Supply. Decouple this pin to signal ground if remote sensing is not used. PGND with a capacitor (0.1µF to 1µF).
ITH1, ITH2 (Pin 4, Pin 5):
Current Control Threshold and
BG1, BG2 (Pin 27, Pin 23):
Bottom Gate Driver Outputs. Error Amplifier Compensation Points. The current com- These pins drive the gates of the bottom N-channel parators’ tripping thresholds increase with these control MOSFETs between INTVCC and PGND. voltages.
BOOST1, BOOST2 (Pin 28, Pin 22):
Boosted Floating
TAVG (Pin 13):
Average Temperature Summing Point. Con- Driver Supplies. The (+) terminal of the booststrap capaci- nect a resistor to ground to sum all currents together for tors connect to these pins. These pins swing from a diode multi-channels or multi-IC operations when temperature voltage drop below INTVCC up to VIN + INTVCC. balancing function is enabled. The value of the resistor
TG1, TG2 (Pin 29, Pin 21):
Top Gate Driver Outputs. These should be the TRSET resistor value divided by the number are the outputs of floating drivers with a voltage swing of channels in the system. Float this pin if thermal balanc- equal to INTV ing is not used. CC superimposed on the switch node voltage.
SW1, SW2 (Pin 30, Pin 20):
Switch Node Connections to
FREQ (Pin 15):
There is a precision 10µA current flowing Inductors. Voltage swing at these pins is from a Schottky out of this pin. A resistor to ground sets a voltage which diode (external) voltage drop below ground to V in turn programs the frequency. Alternatively, this pin can IN. be driven with a DC voltage to vary the frequency of the
CLKOUT (Pin 31):
Clock Output Pin. Clock output with internal oscillator. phase changeable by PHASMD to enable usage of multiple LTC3875s in multiphase systems signal swing is from
IFAST (Pin 17):
Programmable Pin for Fast Transient Op- INTV eration for Channel 2 Only. A resistor to ground programs CC to ground. the threshold of the output load transient excursion. Float this pin to disable this function. See the Applications Information section for more details. 3875fb For more information www.linear.com/LTC3875 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Related Parts
