Datasheet LT1912 (Analog Devices) - 7

LT1912
PIN FUNCTIONS BD (Pin 1):
This pin connects to the anode of the boost
SYNC (Pin 6):
This is the external clock synchronization Schottky diode. BD also supplies current to the internal input. Ground this pin when SYNC function is not used. Tie regulator. to a clock source for synchronization. Clock edges should
BOOST (Pin 2):
This pin is used to provide a drive have rise and fall times faster than 1µs. See synchronizing voltage, higher than the input voltage, to the internal bipolar section in Applications Information. NPN power switch.
N/C (Pin 7):
This pin should be tied to ground.
SW (Pin 3):
The SW pin is the output of the internal power
FB (Pin 8):
The LT1912 regulates the FB pin to 0.790V. switch. Connect this pin to the inductor, catch diode and Connect the feedback resistor divider tap to this pin. boost capacitor.
VC (Pin 9):
The VC pin is the output of the internal error
VIN (Pin 4):
The VIN pin supplies current to the LT1912’s amplifier. The voltage on this pin controls the peak switch internal regulator and to the internal power switch. This current. Tie an RC network from this pin to ground to pin must be locally bypassed. compensate the control loop.
RUN/SS (Pin 5):
The RUN/SS pin is used to put the
RT (Pin 10):
Oscillator Resistor Input. Connecting a resis- LT1912 in shutdown mode. Tie to ground to shut down tor to ground from this pin sets the switching frequency. the LT1912. Tie to 2.5V or more for normal operation. If
GND (Exposed Pad Pin 11):
Ground. The exposed pad the shutdown feature is not used, tie this pin to the VIN must be soldered to PCB. pin. RUN/SS also provides a soft-start function; see the Applications Information section.
BLOCK DIAGRAM
VIN VIN 4 C1 – INTERNAL 0.79V REF + BD 1 RUN/SS 5 ∑ SLOPE COMP SWITCH BOOST LATCH 2 R RT OSCILLATOR C3 Q 10 200kHz–500kHz S RT SW L1 V 3 OUT SYNC 6 C2 D1 SOFT-START ERROR AMP VC CLAMP + VC – 9 CC CF RC GND FB 11 8 R2 R1 1912 BD 1912fa 7 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 Package Description Revision History Typical Application Related Parts