Datasheet LTC3836 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Dual 2-Phase, No RSENSE Low VIN Synchronous Controller |
| Pages / Page | 30 / 1 — FEATURES. DESCRIPTION. No Current Sense Resistors Required. Out-of-Phase … |
| File Format / Size | PDF / 474 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. No Current Sense Resistors Required. Out-of-Phase Controllers Reduce Required Input. Capacitance
Model Line for this Datasheet
Text Version of Document
LTC3836 Dual 2-Phase, No R TM SENSE Low VIN Synchronous Controller
FEATURES DESCRIPTION
n
No Current Sense Resistors Required
The LTC®3836 is a 2-phase dual output synchronous n
Out-of-Phase Controllers Reduce Required Input
step-down switching regulator controller with tracking
Capacitance
that drives external N-channel power MOSFETs using few n
All N-Channel Synchronous Drive
external components. The constant-frequency current n VIN Range: 2.75V to 4.5V mode architecture with MOSFET VDS sensing eliminates n Constant-Frequency Current Mode Operation the need for sense resistors and improves effi ciency. n 0.6V ±1.5% Voltage Reference The power loss and noise due to the ESR of the input n Low Dropout Operation: 97% Duty Cycle capacitance are minimized by operating the two control- n True PLL for Frequency Locking or Adjustment lers out-of-phase. Pulse-skipping operation provides high n Selectable Pulse-Skipping/Continuous Operation effi ciency at light loads. The 97% duty cycle capability n Tracking Function provides low dropout operation, extending operating time n Internal Soft-Start Circuitry in battery-powered systems. n Power Good Output Voltage Monitor The operating frequency is selectable from 300kHz to n Output Overvoltage Protection 750kHz, allowing the use of small surface mount induc- n Micropower Shutdown: IQ = 6.5μA tors and capacitors. For noise sensitive applications, the n Tiny Low Profi le (4mm × 5mm) QFN and Narrow LTC3836 operating frequency can be externally synchro- SSOP Packages nized from 250kHz to 850kHz.
APPLICATIONS
The LTC3836 features an internal 1ms soft-start that can be extended with an external capacitor. A tracking input al- n General Purpose 3.3V to 1.X Supplies lows the second output to track the fi rst during start-up. n Single Lithium-Ion Powered Devices n The LTC3836 is available in the tiny thermally enhanced Distributed DC Power Systems (4mm × 5mm) QFN and 28-lead narrow SSOP packages. L, LT, LTC, LTM, Linear Technology, Burst Mode, OPTI-LOOP and the Linear logo are registered trademarks and No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6144194, 6304066, 6498466, 6580258, 6611131.
TYPICAL APPLICATION High Effi ciency, 2-Phase, Dual Synchronous DC/DC Step-Down Converter Effi ciency/Power Loss vs Load Current
V 100 10000 IN 3.3V-1.8V 3.3V EFFICIENCY V 22 90 IN μF BOOST1 BOOST2 × 3 80 3.3V-1.2V SENSE1+ SENSE2+ EFFICIENCY 1000 POWER LOSS (mW) 70 TG1 TG2 0.47μH 60 SW1 SW2 0.47μH LTC3836 50 100 3.3V-1.2V BG1 BG2 40 POWER LOSS EFFICIENCY (%) PGND 30 118k 59k 3.3V-1.8V V 10 OUT1 V V OUT2 POWER LOSS FB1 VFB2 20 1.8V AT 1.2V AT I I 15A TH1 TH2 820pF 15A 10 SGND 820pF 100 CIRCUIT OF FIGURE 15 μF 59k 100μF 0 1 × 2 59k 15k 15k × 2 10 100 1000 10000 100000 LOAD CURRENT (mA) 3836 TA01b 3836 TA01 3836fb 1 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL CHARACTERISTICS TYPICAL PERFORMANCE CHARACTERISTICS PIN FUNCTIONS FUNCTIONAL DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION REVISION HISTORY RELATED PARTS
FEATURES DESCRIPTION
n
No Current Sense Resistors Required
The LTC®3836 is a 2-phase dual output synchronous n
Out-of-Phase Controllers Reduce Required Input
step-down switching regulator controller with tracking
Capacitance
that drives external N-channel power MOSFETs using few n
All N-Channel Synchronous Drive
external components. The constant-frequency current n VIN Range: 2.75V to 4.5V mode architecture with MOSFET VDS sensing eliminates n Constant-Frequency Current Mode Operation the need for sense resistors and improves effi ciency. n 0.6V ±1.5% Voltage Reference The power loss and noise due to the ESR of the input n Low Dropout Operation: 97% Duty Cycle capacitance are minimized by operating the two control- n True PLL for Frequency Locking or Adjustment lers out-of-phase. Pulse-skipping operation provides high n Selectable Pulse-Skipping/Continuous Operation effi ciency at light loads. The 97% duty cycle capability n Tracking Function provides low dropout operation, extending operating time n Internal Soft-Start Circuitry in battery-powered systems. n Power Good Output Voltage Monitor The operating frequency is selectable from 300kHz to n Output Overvoltage Protection 750kHz, allowing the use of small surface mount induc- n Micropower Shutdown: IQ = 6.5μA tors and capacitors. For noise sensitive applications, the n Tiny Low Profi le (4mm × 5mm) QFN and Narrow LTC3836 operating frequency can be externally synchro- SSOP Packages nized from 250kHz to 850kHz.
APPLICATIONS
The LTC3836 features an internal 1ms soft-start that can be extended with an external capacitor. A tracking input al- n General Purpose 3.3V to 1.X Supplies lows the second output to track the fi rst during start-up. n Single Lithium-Ion Powered Devices n The LTC3836 is available in the tiny thermally enhanced Distributed DC Power Systems (4mm × 5mm) QFN and 28-lead narrow SSOP packages. L, LT, LTC, LTM, Linear Technology, Burst Mode, OPTI-LOOP and the Linear logo are registered trademarks and No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6144194, 6304066, 6498466, 6580258, 6611131.
TYPICAL APPLICATION High Effi ciency, 2-Phase, Dual Synchronous DC/DC Step-Down Converter Effi ciency/Power Loss vs Load Current
V 100 10000 IN 3.3V-1.8V 3.3V EFFICIENCY V 22 90 IN μF BOOST1 BOOST2 × 3 80 3.3V-1.2V SENSE1+ SENSE2+ EFFICIENCY 1000 POWER LOSS (mW) 70 TG1 TG2 0.47μH 60 SW1 SW2 0.47μH LTC3836 50 100 3.3V-1.2V BG1 BG2 40 POWER LOSS EFFICIENCY (%) PGND 30 118k 59k 3.3V-1.8V V 10 OUT1 V V OUT2 POWER LOSS FB1 VFB2 20 1.8V AT 1.2V AT I I 15A TH1 TH2 820pF 15A 10 SGND 820pF 100 CIRCUIT OF FIGURE 15 μF 59k 100μF 0 1 × 2 59k 15k 15k × 2 10 100 1000 10000 100000 LOAD CURRENT (mA) 3836 TA01b 3836 TA01 3836fb 1 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL CHARACTERISTICS TYPICAL PERFORMANCE CHARACTERISTICS PIN FUNCTIONS FUNCTIONAL DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION REVISION HISTORY RELATED PARTS
