Datasheet LT1970A (Analog Devices) - 9

LT1970A
pin FuncTions VCSNK (Pin 12):
Sink Current Limit Control Voltage In- current. The current limit flag is off when the source put. The current sink limit amplifier will activate when current limit is not active. ISRC, ISNK and TSD may be the sense voltage between SENSE+ and SENSE– equals wired “OR” together if desired. ISRC may be left open if –1.0 • VVCSNK/10. VCSNK may be set between VCOMMON this function is not monitored. and VCOMMON + 6V. The transfer function between VCSNK
ISNK (Pin 17):
Sinking Current Limit Digital Output Flag. and VSENSE is linear except for very small input voltages ISNK is an open-collector digital output. ISNK pulls low at VCSNK < 60mV. VSENSE limits at a minimum set point whenever the sinking current limit amplifier assumes of 4mV typical to ensure that the sink and source limit control of the output. This pin can sink up to 10mA of amplifiers do not try to operate simultaneously. To force current. The current limit flag is off when the source zero output current, the ENABLE pin can be taken low. current limit is not active. ISRC, ISNK and TSD may be
VCSRC (Pin 13):
Source Current Limit Control Voltage wired “OR” together if desired. ISNK may be left open if Input. The current source limit amplifier will activate this function is not monitored. when the sense voltage between SENSE+ and SENSE–
TSD (Pin 18):
Thermal Shutdown Digital Output Flag. TSD equals VVCSRC/10. VCSRC may be set between VCOMMON is an open-collector digital output. TSD pulls low whenever and VCOMMON + 6V. The transfer function between VCSRC the internal thermal shutdown circuit activates, typically at and VSENSE is linear except for very small input voltages a die temperature of 160°C. This pin can sink up to 10mA at VCSRC < 60mV. VSENSE limits at a minimum set point of output current. The TSD flag is off when the die tem- of 4mV typical to ensure that the sink and source limit perature is within normal operating temperatures. ISRC, amplifiers do not try to operate simultaneously. To force ISNK and TSD may be wired “OR” together if desired. TSD zero output current, the ENABLE pin can be taken low. may be left open if this function is not monitored. Thermal
COMMON (Pin 14):
Control and ENABLE inputs and flag shutdown activation should prompt the user to evaluate outputs are referenced to the COMMON pin. COMMON electrical loading or thermal environmental conditions. may be at any potential between VEE and VCC – 3V. In
V+ (Pin 19):
Output Stage Positive Supply. V+ may equal typical applications, COMMON is connected to ground. VCC or may be smaller in magnitude. Only output stage
ENABLE (Pin 15):
ENABLE Digital Input Control. When current flows through V+, all other current flows into VCC. taken low this TTL-level digital input turns off the ampli- V+ may be used to drive the base/gate of an external power fier output and drops supply current to less than 1mA. device to boost the amplifier’s output current to levels above Use the ENABLE pin to force zero output current. Setting the rated 500mA of the on-chip output devices. Unless VCSNK = VCSRC = 0V allows IOUT = ±4mV/RSENSE to flow used to drive boost transistors, V+ should be decoupled in or out of VOUT. to ground with a low ESR capacitor.
ISRC (Pin 16):
Sourcing Current Limit Digital Output Flag.
Exposed Pad (Pin 21):
The exposed backside of the pack- ISRC is an open-collector digital output. ISRC pulls low age is electrically connected to the VEE pins on the IC die. whenever the sourcing current limit amplifier assumes The package base should be soldered to a heat spreading control of the output. This pin can sink up to 10mA of pad on the PC board that is electrically connected to VEE. 1970afc For more information www.linear.com/LT1970A 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram And Test Circuit Applications Information Package Description Applications Information Related Parts