Datasheet LT3689, LT3689-5 (Analog Devices)
| Fabricante | Analog Devices |
| Descripción | 700mA Step-Down Regulator with Power-On Reset and Watchdog Timer |
| Páginas / Página | 34 / 1 — FEATURES. DESCRIPTION. Wide Input Range:. Operation from 3.6V to 36V. … |
| Formato / tamaño de archivo | PDF / 986 Kb |
| Idioma del documento | Inglés |
FEATURES. DESCRIPTION. Wide Input Range:. Operation from 3.6V to 36V. Overvoltage Lockout Protects Circuits through
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LT3689/LT3689-5 700mA Step-Down Regulator with Power-On Reset and Watchdog Timer
FEATURES DESCRIPTION
n
Wide Input Range:
The LT®3689 is an adjustable frequency (350kHz to 2.2MHz)
Operation from 3.6V to 36V
monolithic step-down switching regulator with a power-on
Overvoltage Lockout Protects Circuits through
reset and watchdog timer. The regulator operates from
60V Transients
inputs up to 36V and withstands transients up to 60V. Low n
85µA IQ at 12VIN to 3.3VOUT
ripple Burst Mode® operation maintains high efficiency at n
Low Ripple Burst Mode
®
Operation Allows Output
low output current while keeping output ripple below 15mV
Ripple <15mVP-P
in a typical application, with input quiescent current of just n
Programmable, Defeatable Watchdog Timer with
85µA. Shutdown circuitry reduces input supply current to
Window or Timeout Control
less than 1µA while EN/UVLO is pulled low. Using a resis- n
Programmable Power-On Reset Timer (POR)
tor divider on the EN/UVLO pin provides a programmable n
Synchronizable, Adjustable 350kHz to 2.2MHz
undervoltage lockout. Current limit, frequency foldback
Switching Frequency
and thermal shutdown provide fault protection. n 700mA Output Switching Regulator with Internal The reset and watchdog timeout periods are indepen- Power Switch dently adjustable using external capacitors. Tight accuracy n Fixed 5V or Adjustable Output Voltage specifications and glitch immunity ensure reliable reset n 800mV Feedback Voltage operation of a system without false triggering. The open n Programmable Input Undervoltage Lockout with collector RST will pull down if output voltage drops 10% Hysteresis below the programmed value. The watchdog timer is n 16-Pin 3mm × 3mm QFN and 16-Pin MSOP Packages pin-selectable for window or timeout modes. In timeout
APPLICATIONS
mode, WDO pulls low if too long of a period passes before a watchdog transition is detected. In window mode, the n LT3689 monitors for WDI falling edges grouped too close Automotive Electronic Control Units n together or too far apart. Industrial Power Supplies L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION Efficiency 3.3V Regulator with Power-On Reset Timer and Watchdog Timer
90 1000 VIN = 12V VIN 80 VOUT = 3.3V 4.5V TO 36V 2.2µF f = 700kHz TRANSIENT TO 60V VIN EN/UVLO OUT 70 L = 12µH BST POWER LOSS (mW) TA = 25°C µP 0.1µF 12µH 60 100 3.3V I/O WDI SW 700mA 10pF LT3689 50 I/O WDO 40 RESET RST DA 316k EFFICIENCY (%) FB 30 10 CWDT CWDT RT 10nF 20 CPOR CPOR GND SYNC 22µF tWDU = 182ms 20.5k 100k 68nF t 10 WDL = 5.9ms t f RST = 157ms SW = 700kHz 0 1 3689 TA01 0.0001 0.001 0.01 0.1 1 LOAD CURRENT (A) 3689 TA01b 3689fe For more information www.linear.com/LT3689 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Timing Diagrams Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts
FEATURES DESCRIPTION
n
Wide Input Range:
The LT®3689 is an adjustable frequency (350kHz to 2.2MHz)
Operation from 3.6V to 36V
monolithic step-down switching regulator with a power-on
Overvoltage Lockout Protects Circuits through
reset and watchdog timer. The regulator operates from
60V Transients
inputs up to 36V and withstands transients up to 60V. Low n
85µA IQ at 12VIN to 3.3VOUT
ripple Burst Mode® operation maintains high efficiency at n
Low Ripple Burst Mode
®
Operation Allows Output
low output current while keeping output ripple below 15mV
Ripple <15mVP-P
in a typical application, with input quiescent current of just n
Programmable, Defeatable Watchdog Timer with
85µA. Shutdown circuitry reduces input supply current to
Window or Timeout Control
less than 1µA while EN/UVLO is pulled low. Using a resis- n
Programmable Power-On Reset Timer (POR)
tor divider on the EN/UVLO pin provides a programmable n
Synchronizable, Adjustable 350kHz to 2.2MHz
undervoltage lockout. Current limit, frequency foldback
Switching Frequency
and thermal shutdown provide fault protection. n 700mA Output Switching Regulator with Internal The reset and watchdog timeout periods are indepen- Power Switch dently adjustable using external capacitors. Tight accuracy n Fixed 5V or Adjustable Output Voltage specifications and glitch immunity ensure reliable reset n 800mV Feedback Voltage operation of a system without false triggering. The open n Programmable Input Undervoltage Lockout with collector RST will pull down if output voltage drops 10% Hysteresis below the programmed value. The watchdog timer is n 16-Pin 3mm × 3mm QFN and 16-Pin MSOP Packages pin-selectable for window or timeout modes. In timeout
APPLICATIONS
mode, WDO pulls low if too long of a period passes before a watchdog transition is detected. In window mode, the n LT3689 monitors for WDI falling edges grouped too close Automotive Electronic Control Units n together or too far apart. Industrial Power Supplies L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION Efficiency 3.3V Regulator with Power-On Reset Timer and Watchdog Timer
90 1000 VIN = 12V VIN 80 VOUT = 3.3V 4.5V TO 36V 2.2µF f = 700kHz TRANSIENT TO 60V VIN EN/UVLO OUT 70 L = 12µH BST POWER LOSS (mW) TA = 25°C µP 0.1µF 12µH 60 100 3.3V I/O WDI SW 700mA 10pF LT3689 50 I/O WDO 40 RESET RST DA 316k EFFICIENCY (%) FB 30 10 CWDT CWDT RT 10nF 20 CPOR CPOR GND SYNC 22µF tWDU = 182ms 20.5k 100k 68nF t 10 WDL = 5.9ms t f RST = 157ms SW = 700kHz 0 1 3689 TA01 0.0001 0.001 0.01 0.1 1 LOAD CURRENT (A) 3689 TA01b 3689fe For more information www.linear.com/LT3689 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Timing Diagrams Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts