Datasheet LT3688 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Dual 800mA Step-Down Switching Regulator with Power-On Reset and Watchdog Timer |
| Pages / Page | 28 / 1 — FEATURES. DESCRIPTION. Wide Input Range:. Operation from 3.8V to 36V. Low … |
| File Format / Size | PDF / 430 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide Input Range:. Operation from 3.8V to 36V. Low Ripple (<25mVP-P ) Burst Mode Operation:
Model Line for this Datasheet
Text Version of Document
LT3688 Dual 800mA Step-Down Switching Regulator with Power-On Reset and Watchdog Timer
FEATURES DESCRIPTION
n
Wide Input Range:
The LT®3688 is an adjustable frequency (350kHz to
Operation from 3.8V to 36V
2.2MHz) dual monolithic step-down switching regulator n
Low Ripple (<25mVP-P ) Burst Mode Operation:
with two power-on reset timers and a watchdog timer.
IQ = 115μA at 12VIN to 3.3V and 5V
The regulator operates off inputs up to 36V. Low ripple n
Programmable, Defeatable Window Watchdog Timer
Burst Mode® operation maintains high effi ciency at low n
Two Independently Programmable Power-On-Reset
output current while keeping output ripple below 25mV in
Timers
a typical application, with input quiescent current of just n
Synchronizable, Adjustable 350kHz-2.2MHz
115μA. Shutdown circuitry reduces input supply current
Switching Frequency
to less than 1μA while EN/UVLO is pulled low. n Two 800mA Output Switching Regulators with Internal The reset and watchdog timeout periods are both adjust- Power Switches able using external capacitors. Tight accuracy specifi ca- n Programmable Input Undervoltage Lockout with tions and glitch immunity ensure reliable reset operation Hysteresis without false triggering. The open collector RST pins will n Thermally Enhanced 24-Pin TSSOP and 4mm × 4mm pull down if the monitored output voltage drops 10% QFN Packages below the programmed value. The LT3688 watchdog timer
APPLICATIONS
monitors for watchdog falling edges grouped too close together or too far apart. n Automotive Electronic Control Units The LT3688 is available in 24-Pin TSSOP and 4mm × n Industrial Power Supplies 4mm QFN packages, each with an exposed pad for low n High-Reliability μProcessor Systems thermal resistance. L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION 5V and 3.3V Regulator with Power-On Reset and Watchdog Timers Effi ciency
VIN 90 10000.0 6V TO 36V VIN = 12V 4.7μF VOUT = 3.3V EN/UVLO VIN BIAS 80 L = 4.7μH 1000.0 BST1 BST2 f = 800kHz POWER LOSS (mW) V 18μH 0.22μF OUT1 0.22μF 12μH VOUT2 5V 70 100.0 SW1 SW2 3.3V 800mA 800mA LT3688 523k 316k 22pF DA1 DA2 22pF 60 10.0 FB1 FB2 22μF 100k 1nF 1nF 100k 22μF EFFICIENCY (%) 50 1.0 RUN/SS1 RUN/SS2 40 0.1 μP CWDT I/O WDI CPOR1 I/O WDO 1nF C 30 0.01 RESET RST1 POR2 4.7nF 0.0001 0.001 0.01 0.1 1 RST2 RT 4.7nF LOAD CURRENT (A) GND SYNC 3688 TA01b 110k 3688 TA01a fSW = 500kHz 3688f 1
FEATURES DESCRIPTION
n
Wide Input Range:
The LT®3688 is an adjustable frequency (350kHz to
Operation from 3.8V to 36V
2.2MHz) dual monolithic step-down switching regulator n
Low Ripple (<25mVP-P ) Burst Mode Operation:
with two power-on reset timers and a watchdog timer.
IQ = 115μA at 12VIN to 3.3V and 5V
The regulator operates off inputs up to 36V. Low ripple n
Programmable, Defeatable Window Watchdog Timer
Burst Mode® operation maintains high effi ciency at low n
Two Independently Programmable Power-On-Reset
output current while keeping output ripple below 25mV in
Timers
a typical application, with input quiescent current of just n
Synchronizable, Adjustable 350kHz-2.2MHz
115μA. Shutdown circuitry reduces input supply current
Switching Frequency
to less than 1μA while EN/UVLO is pulled low. n Two 800mA Output Switching Regulators with Internal The reset and watchdog timeout periods are both adjust- Power Switches able using external capacitors. Tight accuracy specifi ca- n Programmable Input Undervoltage Lockout with tions and glitch immunity ensure reliable reset operation Hysteresis without false triggering. The open collector RST pins will n Thermally Enhanced 24-Pin TSSOP and 4mm × 4mm pull down if the monitored output voltage drops 10% QFN Packages below the programmed value. The LT3688 watchdog timer
APPLICATIONS
monitors for watchdog falling edges grouped too close together or too far apart. n Automotive Electronic Control Units The LT3688 is available in 24-Pin TSSOP and 4mm × n Industrial Power Supplies 4mm QFN packages, each with an exposed pad for low n High-Reliability μProcessor Systems thermal resistance. L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION 5V and 3.3V Regulator with Power-On Reset and Watchdog Timers Effi ciency
VIN 90 10000.0 6V TO 36V VIN = 12V 4.7μF VOUT = 3.3V EN/UVLO VIN BIAS 80 L = 4.7μH 1000.0 BST1 BST2 f = 800kHz POWER LOSS (mW) V 18μH 0.22μF OUT1 0.22μF 12μH VOUT2 5V 70 100.0 SW1 SW2 3.3V 800mA 800mA LT3688 523k 316k 22pF DA1 DA2 22pF 60 10.0 FB1 FB2 22μF 100k 1nF 1nF 100k 22μF EFFICIENCY (%) 50 1.0 RUN/SS1 RUN/SS2 40 0.1 μP CWDT I/O WDI CPOR1 I/O WDO 1nF C 30 0.01 RESET RST1 POR2 4.7nF 0.0001 0.001 0.01 0.1 1 RST2 RT 4.7nF LOAD CURRENT (A) GND SYNC 3688 TA01b 110k 3688 TA01a fSW = 500kHz 3688f 1
