Datasheet LTC1702A (Analog Devices) - 5
| Manufacturer | Analog Devices |
| Description | Dual 550kHz Synchronous 2-Phase Switching Regulator Controller |
| Pages / Page | 36 / 5 — PIN FUNCTIONS. CC (Pin 1):. BOOST1 (Pin 2):. PGOOD1 (Pin 7):. FCB (Pin … |
| File Format / Size | PDF / 427 Kb |
| Document Language | English |
PIN FUNCTIONS. CC (Pin 1):. BOOST1 (Pin 2):. PGOOD1 (Pin 7):. FCB (Pin 8):. BG1 (Pin 3):. RUN/SS1 (Pin 9):. TG1 (Pin 4):
Model Line for this Datasheet
Text Version of Document
LTC1702A
U U U PIN FUNCTIONS PV
controller 1. If the voltage drop across the bottom MOSFET,
CC (Pin 1):
Driver Power Supply Input. PVCC provides power to the two BGn output drivers. PV QB1, exceeds the magnitude of the voltage at I CC must be MAX1, connected to a voltage high enough to fully turn on the controller 1 will go into current limit. The IMAX1 pin has an external MOSFETs QB1 and QB2. PV internal 10 CC should generally µA current source pull-up, allowing the current be connected directly to V threshold to be set with a single external resistor to PGND. IN. PVCC requires at least a 1µF bypass capacitor directly to PGND. See the Current Limit Programming section for more information on choosing RIMAX.
BOOST1 (Pin 2):
Controller 1 Top Gate Driver Supply. The BOOST1 pin supplies power to the floating TG1 driver.
PGOOD1 (Pin 7):
Controller 1 Power Good. PGOOD1 is an BOOST1 should be bypassed to SW1 with a 1µF capacitor. open-drain logic output. PGOOD1 will pull low whenever An additional Schottky diode from V FB1 IN to BOOST1 pin will falls 5% below its programmed value. When RUN/SS1 create a complete floating charge-pumped supply at is low (side 1 shut down), PGOOD1 will go high. BOOST1. No other external supplies are required. A 5Ω to
FCB (Pin 8):
Force Continuous Bar. The FCB pin forces 10Ω resistor in series with this pin can help control ringing both converters to maintain continuous synchronous at the switch node. See the EXTERNAL COMPONENTS operation regardless of load when the voltage at FCB SELECTION/MOSFET Series Resistors section for more drops below 0.8V. FCB is normally tied to VCC. To force information. continuous operation, tie FCB to SGND. FCB can also be
BG1 (Pin 3):
Controller 1 Bottom Gate Drive. The BG1 pin connected to a feedback resistor divider from a secondary drives the gate of the bottom N-channel synchronous winding on one converter’s inductor to generate a third switch MOSFET, QB1. BG1 is designed to drive up to regulated output voltage. Do not leave FCB floating. 10,000pF of gate capacitance directly. If RUN/SS1 goes
RUN/SS1 (Pin 9):
Controller 1 Run/Soft-start. Pulling low, BG1 will go low, turning off QB1. If FAULT mode is RUN/SS1 to SGND will disable controller 1 and turn off tripped, BG1 will go high and stay high, keeping QB1 on both of its external MOSFET switches. Pulling both until the VCC is cycled. BG1 should be directly connected RUN/SS pins down will shut down the entire LTC1702A, to the MOSFET gate. Do not use a series resistor. See the dropping the quiescent supply current below 100µA. A EXTERNAL COMPONENTS SELECTION/MOSFET Series capacitor from RUN/SS1 to SGND will control the turn-on Resistors section for more information. time and rate of rise of the controller 1 output voltage at
TG1 (Pin 4):
Controller 1 Top Gate Drive. The TG1 pin drives power-up. An internal 3.5µA current source pull-up at the gate of the top N-channel MOSFET, QT1. The TG1 driver RUN/SS1 pin sets the turn-on time at approximately draws power from the BOOST1 pin and returns to the SW1 500ms/µF. pin, providing true floating drive to QT1. TG1 is designed to
COMP1 (Pin 10):
Controller 1 Loop Compensation. The drive up to 10,000pF of gate capacitance directly. In COMP1 pin is connected directly to the output of the first shutdown or fault modes, TG1 will go low. TG1 should be controller’s error amplifier and the input to the PWM directly connected to the MOSFET gate. Do not use a series comparator. An RC network is used at the COMP1 pin to resistor. See the EXTERNAL COMPONENTS SELECTION/ compensate the feedback loop for optimum transient MOSFET Series Resistors section for more information. response.
SW1 (Pin 5):
Controller 1 Switching Node. SW1 should be
SGND (Pin 11):
Signal Ground. All internal low power connected to the switching node of converter 1. The TG1 circuitry returns to the SGND pin. Connect to a low driver ground returns to SW1, providing floating gate impedance ground, separated from the PGND node. All drive to the top N-channel MOSFET switch, QT1. The feedback, compensation and soft-start connections should voltage at SW1 is compared to IMAX1 by the current limit return to SGND. SGND and PGND should connect only at comparator while the bottom MOSFET, QB1, is on. a single point, near the PGND pin and the negative plate of
I
the C
MAX1 (Pin 6):
Controller 1 Current Limit Set. The IMAX1 IN bypass capacitor. pin sets the current limit comparator threshold for 1702afa 5
U U U PIN FUNCTIONS PV
controller 1. If the voltage drop across the bottom MOSFET,
CC (Pin 1):
Driver Power Supply Input. PVCC provides power to the two BGn output drivers. PV QB1, exceeds the magnitude of the voltage at I CC must be MAX1, connected to a voltage high enough to fully turn on the controller 1 will go into current limit. The IMAX1 pin has an external MOSFETs QB1 and QB2. PV internal 10 CC should generally µA current source pull-up, allowing the current be connected directly to V threshold to be set with a single external resistor to PGND. IN. PVCC requires at least a 1µF bypass capacitor directly to PGND. See the Current Limit Programming section for more information on choosing RIMAX.
BOOST1 (Pin 2):
Controller 1 Top Gate Driver Supply. The BOOST1 pin supplies power to the floating TG1 driver.
PGOOD1 (Pin 7):
Controller 1 Power Good. PGOOD1 is an BOOST1 should be bypassed to SW1 with a 1µF capacitor. open-drain logic output. PGOOD1 will pull low whenever An additional Schottky diode from V FB1 IN to BOOST1 pin will falls 5% below its programmed value. When RUN/SS1 create a complete floating charge-pumped supply at is low (side 1 shut down), PGOOD1 will go high. BOOST1. No other external supplies are required. A 5Ω to
FCB (Pin 8):
Force Continuous Bar. The FCB pin forces 10Ω resistor in series with this pin can help control ringing both converters to maintain continuous synchronous at the switch node. See the EXTERNAL COMPONENTS operation regardless of load when the voltage at FCB SELECTION/MOSFET Series Resistors section for more drops below 0.8V. FCB is normally tied to VCC. To force information. continuous operation, tie FCB to SGND. FCB can also be
BG1 (Pin 3):
Controller 1 Bottom Gate Drive. The BG1 pin connected to a feedback resistor divider from a secondary drives the gate of the bottom N-channel synchronous winding on one converter’s inductor to generate a third switch MOSFET, QB1. BG1 is designed to drive up to regulated output voltage. Do not leave FCB floating. 10,000pF of gate capacitance directly. If RUN/SS1 goes
RUN/SS1 (Pin 9):
Controller 1 Run/Soft-start. Pulling low, BG1 will go low, turning off QB1. If FAULT mode is RUN/SS1 to SGND will disable controller 1 and turn off tripped, BG1 will go high and stay high, keeping QB1 on both of its external MOSFET switches. Pulling both until the VCC is cycled. BG1 should be directly connected RUN/SS pins down will shut down the entire LTC1702A, to the MOSFET gate. Do not use a series resistor. See the dropping the quiescent supply current below 100µA. A EXTERNAL COMPONENTS SELECTION/MOSFET Series capacitor from RUN/SS1 to SGND will control the turn-on Resistors section for more information. time and rate of rise of the controller 1 output voltage at
TG1 (Pin 4):
Controller 1 Top Gate Drive. The TG1 pin drives power-up. An internal 3.5µA current source pull-up at the gate of the top N-channel MOSFET, QT1. The TG1 driver RUN/SS1 pin sets the turn-on time at approximately draws power from the BOOST1 pin and returns to the SW1 500ms/µF. pin, providing true floating drive to QT1. TG1 is designed to
COMP1 (Pin 10):
Controller 1 Loop Compensation. The drive up to 10,000pF of gate capacitance directly. In COMP1 pin is connected directly to the output of the first shutdown or fault modes, TG1 will go low. TG1 should be controller’s error amplifier and the input to the PWM directly connected to the MOSFET gate. Do not use a series comparator. An RC network is used at the COMP1 pin to resistor. See the EXTERNAL COMPONENTS SELECTION/ compensate the feedback loop for optimum transient MOSFET Series Resistors section for more information. response.
SW1 (Pin 5):
Controller 1 Switching Node. SW1 should be
SGND (Pin 11):
Signal Ground. All internal low power connected to the switching node of converter 1. The TG1 circuitry returns to the SGND pin. Connect to a low driver ground returns to SW1, providing floating gate impedance ground, separated from the PGND node. All drive to the top N-channel MOSFET switch, QT1. The feedback, compensation and soft-start connections should voltage at SW1 is compared to IMAX1 by the current limit return to SGND. SGND and PGND should connect only at comparator while the bottom MOSFET, QB1, is on. a single point, near the PGND pin and the negative plate of
I
the C
MAX1 (Pin 6):
Controller 1 Current Limit Set. The IMAX1 IN bypass capacitor. pin sets the current limit comparator threshold for 1702afa 5
