Datasheet LT3487 (Analog Devices) - 6
| Manufacturer | Analog Devices |
| Description | Boost and Inverting Switching Regulator for CCD Bias |
| Pages / Page | 16 / 6 — PI FU CTIO S. CAP (Pin 1):. RUN/SS (Pin 8):. SWP (Pin 2):. VBAT (Pin 3):. … |
| File Format / Size | PDF / 296 Kb |
| Document Language | English |
PI FU CTIO S. CAP (Pin 1):. RUN/SS (Pin 8):. SWP (Pin 2):. VBAT (Pin 3):. SWN (Pin 4):. FBP (Pin 9):. DN (Pin 5):. VIN (Pin 6):
Model Line for this Datasheet
Text Version of Document
LT3487
U U U PI FU CTIO S CAP (Pin 1):
Disconnect-PNP Emitter and Positive Schottky
RUN/SS (Pin 8):
Run/Soft-Start Pin. Connect to an open- Cathode. Acts as an intermediate positive (boost) output. drain transistor. The transistor must sink 1.4µA from Connect boost output capacitor to this pin. RUN/SS. Pull RUN/SS below 100mV to shut down the chip. Connect a capacitor from RUN/SS to ground to program
SWP (Pin 2):
Switch Pin and Schottky Anode for Positive soft-start functionality. The soft-start will slowly bring the Channel. Connect boost inductor to this pin. boost channel into regulation and then slowly bring up
VBAT (Pin 3):
Battery Voltage. Connect this pin to the sup- the inverter. RUN/SS must be above 1.6V to allow both ply voltage for the boost inductor. The disconnect drive channels to reach full current. If soft-start is not required, current is returned to this pin. The disconnect operates this pin can be driven with a logic signal, but the RUN/SS until CAP falls to 1.2V above VBAT. voltage must remain below VIN.
SWN (Pin 4):
Switch Pin for Negative (Inverter) Chan-
FBP (Pin 9):
Feedback Pin for Boost. Connect boost nel. Connect inverter input inductor and fl ying capacitor feedback resistor R1 from FBP to CAP. Choose R1 ac- here. cording to:
DN (Pin 5):
Anode of Internal Schottky for Inverter. Connect VPOS – 1.23 inverter output inductor and fl ying capacitor here. R1= µA 25
VIN (Pin 6):
Input Supply Pin. VIN is used to power the Pin voltage = 1.23V when regulated. control circuitry of the LT3487. This pin must be locally bypassed with an X5R or X7R type ceramic capacitor.
VPOS (Pin 10):
Output Pin for Boost Channel. VPOS is the collector of the output disconnect PNP. Connect the
FBN (Pin 7):
Feedback Pin for Inverter. Connect feedback boost load to V resistor R2 from this pin to V POS. Connect capacitor C5 between CAP NEG. Choose R2 according and V to: POS for stability. V
Exposed Pad (Pin 11):
GND. Tie directly to ground plane R NEG 2 = – through multiple vias under the package for optimum µA 25 thermal performance. Pin voltage = 0V when regulated. 3487f 6
U U U PI FU CTIO S CAP (Pin 1):
Disconnect-PNP Emitter and Positive Schottky
RUN/SS (Pin 8):
Run/Soft-Start Pin. Connect to an open- Cathode. Acts as an intermediate positive (boost) output. drain transistor. The transistor must sink 1.4µA from Connect boost output capacitor to this pin. RUN/SS. Pull RUN/SS below 100mV to shut down the chip. Connect a capacitor from RUN/SS to ground to program
SWP (Pin 2):
Switch Pin and Schottky Anode for Positive soft-start functionality. The soft-start will slowly bring the Channel. Connect boost inductor to this pin. boost channel into regulation and then slowly bring up
VBAT (Pin 3):
Battery Voltage. Connect this pin to the sup- the inverter. RUN/SS must be above 1.6V to allow both ply voltage for the boost inductor. The disconnect drive channels to reach full current. If soft-start is not required, current is returned to this pin. The disconnect operates this pin can be driven with a logic signal, but the RUN/SS until CAP falls to 1.2V above VBAT. voltage must remain below VIN.
SWN (Pin 4):
Switch Pin for Negative (Inverter) Chan-
FBP (Pin 9):
Feedback Pin for Boost. Connect boost nel. Connect inverter input inductor and fl ying capacitor feedback resistor R1 from FBP to CAP. Choose R1 ac- here. cording to:
DN (Pin 5):
Anode of Internal Schottky for Inverter. Connect VPOS – 1.23 inverter output inductor and fl ying capacitor here. R1= µA 25
VIN (Pin 6):
Input Supply Pin. VIN is used to power the Pin voltage = 1.23V when regulated. control circuitry of the LT3487. This pin must be locally bypassed with an X5R or X7R type ceramic capacitor.
VPOS (Pin 10):
Output Pin for Boost Channel. VPOS is the collector of the output disconnect PNP. Connect the
FBN (Pin 7):
Feedback Pin for Inverter. Connect feedback boost load to V resistor R2 from this pin to V POS. Connect capacitor C5 between CAP NEG. Choose R2 according and V to: POS for stability. V
Exposed Pad (Pin 11):
GND. Tie directly to ground plane R NEG 2 = – through multiple vias under the package for optimum µA 25 thermal performance. Pin voltage = 0V when regulated. 3487f 6
