Datasheet LT1425 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Isolated Flyback Switching Regulators |
| Pages / Page | 20 / 1 — FEATURES. DESCRIPTION. No Transformer “Third Winding” or Optoisolator. … |
| File Format / Size | PDF / 302 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. No Transformer “Third Winding” or Optoisolator. Required. 5% Accurate Output Voltage Without User Trims
Model Line for this Datasheet
Text Version of Document
LT1425 Isolated Flyback Switching Regulator
U FEATURES DESCRIPTION
■
No Transformer “Third Winding” or Optoisolator
The LT®1425 is a monolithic high power switching regu-
Required
lator specifically designed for the isolated flyback topol- ■ ±
5% Accurate Output Voltage Without User Trims
ogy. No “third winding” or optoisolator is required; the
(See Circuit Below)
integrated circuit senses the isolated output voltage ■ Resistor Programmable Output Voltage directly from the primary side flyback waveform. A high ■
Regulation Maintained Well Into Discontinuous
current, high efficiency switch is included on the die along
Mode (Light Load)
with all oscillator, control and protection circuitry. ■ Optional Load Compensation The LT1425 operates with input supply voltages from 3V ■ Operating Frequency: 285kHz to 20V and draws only 7mA quiescent current. It can ■ Easily Synchronized to External Clock deliver output power up to 6W with no external power ■ Available in 16-Pin Narrow SO Package devices. By utilizing current mode switching techniques, it
U
provides excellent AC and DC line regulation.
APPLICATIONS
The LT1425 has a number of features not found on other ■ Isolated Flyback Switching Regulators switching regulator ICs. Its unique control circuitry can ■ Ethernet Isolated 5V to – 9V Converters maintain regulation well into discontinuous mode in most ■ Medical Instruments applications. Optional load compensation circuitry allows ■ Isolated Telecom Supplies for improved load regulation. An externally activated shut- down mode reduces total supply current to 15µA for , LTC and LT are registered trademarks of Linear Technology Corporation. standby operation.
U TYPICAL APPLICATION 5V to Isolated – 9VOUT Load Regulation
500V ISOLATION BARRIER 9.5 5V 9.4 T1* V – + C1 9.3 C2 ISOLATED D1 100µF 12 47µF 9.2 1N5819 + –9V ± 5% AT 10V 16V 20mA TO 200mA VIN 11 • • 9.1 VSW R1 9.0 22.6k F LT1425 1% 8.9 *DALE LPE 4841-330MB 15 3 SHDN RFB 8.8 6 R2 OUTPUT VOLTAGE (V) SYNC 3.01k 8.7 4 5 1% V R C REF 8.6 C3 14 R 1000pF OCOMP 8.5 13 R R3 0 50 100 150 200 CCOMP C4 15k OUTPUT CURRENT (mA) SGND PGND 0.1µF 7 10 1425 TA02 1425 TA01 1
U FEATURES DESCRIPTION
■
No Transformer “Third Winding” or Optoisolator
The LT®1425 is a monolithic high power switching regu-
Required
lator specifically designed for the isolated flyback topol- ■ ±
5% Accurate Output Voltage Without User Trims
ogy. No “third winding” or optoisolator is required; the
(See Circuit Below)
integrated circuit senses the isolated output voltage ■ Resistor Programmable Output Voltage directly from the primary side flyback waveform. A high ■
Regulation Maintained Well Into Discontinuous
current, high efficiency switch is included on the die along
Mode (Light Load)
with all oscillator, control and protection circuitry. ■ Optional Load Compensation The LT1425 operates with input supply voltages from 3V ■ Operating Frequency: 285kHz to 20V and draws only 7mA quiescent current. It can ■ Easily Synchronized to External Clock deliver output power up to 6W with no external power ■ Available in 16-Pin Narrow SO Package devices. By utilizing current mode switching techniques, it
U
provides excellent AC and DC line regulation.
APPLICATIONS
The LT1425 has a number of features not found on other ■ Isolated Flyback Switching Regulators switching regulator ICs. Its unique control circuitry can ■ Ethernet Isolated 5V to – 9V Converters maintain regulation well into discontinuous mode in most ■ Medical Instruments applications. Optional load compensation circuitry allows ■ Isolated Telecom Supplies for improved load regulation. An externally activated shut- down mode reduces total supply current to 15µA for , LTC and LT are registered trademarks of Linear Technology Corporation. standby operation.
U TYPICAL APPLICATION 5V to Isolated – 9VOUT Load Regulation
500V ISOLATION BARRIER 9.5 5V 9.4 T1* V – + C1 9.3 C2 ISOLATED D1 100µF 12 47µF 9.2 1N5819 + –9V ± 5% AT 10V 16V 20mA TO 200mA VIN 11 • • 9.1 VSW R1 9.0 22.6k F LT1425 1% 8.9 *DALE LPE 4841-330MB 15 3 SHDN RFB 8.8 6 R2 OUTPUT VOLTAGE (V) SYNC 3.01k 8.7 4 5 1% V R C REF 8.6 C3 14 R 1000pF OCOMP 8.5 13 R R3 0 50 100 150 200 CCOMP C4 15k OUTPUT CURRENT (mA) SGND PGND 0.1µF 7 10 1425 TA02 1425 TA01 1
