Datasheet LT4351 (Analog Devices) - 6
| Manufacturer | Analog Devices |
| Description | MOSFET Diode-OR Controller |
| Pages / Page | 20 / 6 — PIN FUNCTIONS. GATE (Pin 1):. DD (Pin 2):. UV (Pin 7):. IN (Pin 3):. … |
| File Format / Size | PDF / 346 Kb |
| Document Language | English |
PIN FUNCTIONS. GATE (Pin 1):. DD (Pin 2):. UV (Pin 7):. IN (Pin 3):. FAULT (Pin 8):. SW (Pin 4):. GND (Pin 5):. STATUS (Pin 9):
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Text Version of Document
LT4351
PIN FUNCTIONS GATE (Pin 1):
MOSFET Gate Drive Pin. This pin is tied to fault. Overvoltage detection has filtering on it to prevent the gate(s) of the external N-channel MOSFET(s). The GATE false triggering. The filtering depends on the level of over- pin drives high when UV is above the VUV(TH) threshold, drive. Filtered tripping will occur when OV exceeds 0.3V. OV is below the VOV(TH) threshold and VIN is greater than If OV exceeds 0.33V, the gate immediately turns off (no OUT by 15mV. When not driven high, GATE actively pulls filtering). If overvoltage detection is not required, ground to GND. GATE can sink or source up to 600mA. the OV pin. See the Applications Information section for
V
further information.
DD (Pin 2):
Gate Drive Supply Pin. This is the supply pin for the gate drive amplifier. It is either generated by
UV (Pin 7):
Undervoltage Shutdown Pin. This pin is used the onboard boost regulator or supplied externally. When for the undervoltage detect function. It is connected to turning on the MOSFET(s), a large high current pulse a resistive divider from VIN. When the voltage is below flows through this pin. Bypass the pin with a 1µF capaci- the UV threshold, GATE pulls to GND disabling power tor placed in close proximity to the part. The voltage on transfer. In addition, the FAULT pin pulls low indicating a this pin is also the feedback for the boost regulator. If the fault. When the UV pin voltage drops below the threshold, VDD voltage exceeds the VIN voltage by 10.7V, the boost a 10µA current is pulled from the divider to provide hys- switch is held off. teresis. If undervoltage detection is not required, tie the
V
UV pin to a voltage greater than 320mV and not greater
IN (Pin 3):
Input Supply Pin. This pin is the supply pin for the control circuitry and the boost regulator. It is also than VIN. Do not force more than 9V on UV due to an one input in conjunction with OUT for controlling the internal clamp. See the Applications Information section MOSFET(s). Bypassing should include a low ESR/ESL for further information. capacitor placed in close proximity to the part.
FAULT (Pin 8):
Fault Comparator Status Pin. This pin pulls
SW (Pin 4):
Boost Regulator Switch Pin. This pin is the low when a fault occurs. A fault has occurred if the UV pin boost regulator switch output. It is connected to the boost is below threshold or the OV pin is above threshold. The inductor and the boost diode. Peak switch current is limited FAULT pin low indicates that there is a problem with the internally to 450mA. A Schottky diode between GND and VIN (source) supply. GATE is pulled to GND during a fault, SW is required. If an external V disabling the MOSFET(s) and prohibits common supply DD supply is used, leave this pin open. contamination. If the GATE pin goes to compliance (GATE equals the lesser of VDD – 2.3V or OUT + 7.4V) and VIN is
GND (Pin 5):
Device Ground Pin. This pin is ground for the greater than OUT by more than 0.21V, FAULT turns on as boost switch, gate driver as well as the control circuitry. an indicator that the MOSFETs are probably not function- Tie the VIN and VDD bypass capacitors and ground plane ing. Leave this pin open if not used. close to this pin to minimize the effects of switching cur- rents on part performance.
STATUS (Pin 9):
MOSFET Status Pin. This pin pulls low when GATE is above VIN by more than 0.7V and VIN is
OV (Pin 6):
Overvoltage Shutdown Pin. This pin is used greater than OUT by 15mV. This indicates the MOSFET is for input overvoltage detection. It is connected to a resis- on. Leave this pin open if not used. tive divider from VIN. When the voltage exceeds the OV threshold (0.3V), GATE is pulled to GND disabling power
OUT (Pin 10):
Common Supply Pin. This pin is connected transfer. In addition, the FAULT pin pulls low indicating a to the supply common and is used in conjunction with VIN as one input controlling the MOSFET(s). 4351fd 6 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 Package Description Revision History Typical Application Related Parts
PIN FUNCTIONS GATE (Pin 1):
MOSFET Gate Drive Pin. This pin is tied to fault. Overvoltage detection has filtering on it to prevent the gate(s) of the external N-channel MOSFET(s). The GATE false triggering. The filtering depends on the level of over- pin drives high when UV is above the VUV(TH) threshold, drive. Filtered tripping will occur when OV exceeds 0.3V. OV is below the VOV(TH) threshold and VIN is greater than If OV exceeds 0.33V, the gate immediately turns off (no OUT by 15mV. When not driven high, GATE actively pulls filtering). If overvoltage detection is not required, ground to GND. GATE can sink or source up to 600mA. the OV pin. See the Applications Information section for
V
further information.
DD (Pin 2):
Gate Drive Supply Pin. This is the supply pin for the gate drive amplifier. It is either generated by
UV (Pin 7):
Undervoltage Shutdown Pin. This pin is used the onboard boost regulator or supplied externally. When for the undervoltage detect function. It is connected to turning on the MOSFET(s), a large high current pulse a resistive divider from VIN. When the voltage is below flows through this pin. Bypass the pin with a 1µF capaci- the UV threshold, GATE pulls to GND disabling power tor placed in close proximity to the part. The voltage on transfer. In addition, the FAULT pin pulls low indicating a this pin is also the feedback for the boost regulator. If the fault. When the UV pin voltage drops below the threshold, VDD voltage exceeds the VIN voltage by 10.7V, the boost a 10µA current is pulled from the divider to provide hys- switch is held off. teresis. If undervoltage detection is not required, tie the
V
UV pin to a voltage greater than 320mV and not greater
IN (Pin 3):
Input Supply Pin. This pin is the supply pin for the control circuitry and the boost regulator. It is also than VIN. Do not force more than 9V on UV due to an one input in conjunction with OUT for controlling the internal clamp. See the Applications Information section MOSFET(s). Bypassing should include a low ESR/ESL for further information. capacitor placed in close proximity to the part.
FAULT (Pin 8):
Fault Comparator Status Pin. This pin pulls
SW (Pin 4):
Boost Regulator Switch Pin. This pin is the low when a fault occurs. A fault has occurred if the UV pin boost regulator switch output. It is connected to the boost is below threshold or the OV pin is above threshold. The inductor and the boost diode. Peak switch current is limited FAULT pin low indicates that there is a problem with the internally to 450mA. A Schottky diode between GND and VIN (source) supply. GATE is pulled to GND during a fault, SW is required. If an external V disabling the MOSFET(s) and prohibits common supply DD supply is used, leave this pin open. contamination. If the GATE pin goes to compliance (GATE equals the lesser of VDD – 2.3V or OUT + 7.4V) and VIN is
GND (Pin 5):
Device Ground Pin. This pin is ground for the greater than OUT by more than 0.21V, FAULT turns on as boost switch, gate driver as well as the control circuitry. an indicator that the MOSFETs are probably not function- Tie the VIN and VDD bypass capacitors and ground plane ing. Leave this pin open if not used. close to this pin to minimize the effects of switching cur- rents on part performance.
STATUS (Pin 9):
MOSFET Status Pin. This pin pulls low when GATE is above VIN by more than 0.7V and VIN is
OV (Pin 6):
Overvoltage Shutdown Pin. This pin is used greater than OUT by 15mV. This indicates the MOSFET is for input overvoltage detection. It is connected to a resis- on. Leave this pin open if not used. tive divider from VIN. When the voltage exceeds the OV threshold (0.3V), GATE is pulled to GND disabling power
OUT (Pin 10):
Common Supply Pin. This pin is connected transfer. In addition, the FAULT pin pulls low indicating a to the supply common and is used in conjunction with VIN as one input controlling the MOSFET(s). 4351fd 6 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 Package Description Revision History Typical Application Related Parts
