Datasheet LTC1876 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | High Efficiency, 2-Phase, Dual Synchronous Step-Down Switching Controller and Step-Up Regulator |
| Pages / Page | 36 / 1 — FEATURES. DESCRIPTIO. Step-Down Controller. Out-of-Phase Controllers … |
| File Format / Size | PDF / 372 Kb |
| Document Language | English |
FEATURES. DESCRIPTIO. Step-Down Controller. Out-of-Phase Controllers Reduce Required Input
Model Line for this Datasheet
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LTC1876 High Efficiency, 2-Phase, Dual Synchronous Step-Down Switching Controller and Step-Up Regulator
U FEATURES DESCRIPTIO Step-Down Controller
The LTC®1876 is a high performance triple output switching ■
Out-of-Phase Controllers Reduce Required Input
regulator. It incorporates a dual step-down switching con-
Capacitance and Power Supply Induced Noise
troller that drives all N-channel synchronous power MOSFET ■
Power Good Output Voltage Indicator
stages. A step-up regulator with an internal 1A, 36V switch ■ OPTI-LOOPTM Compensation Minimizes C provides the third output. OUT ■ DC Programmed Fixed Frequency 150kHz to 300kHz The step-down controllers minimize power loss and noise ■ Wide VIN Range: 3.5V to 36V Operation by operating the output stage of each controller out of ■ Very Low Dropout Operation: 99% Duty Cycle phase. OPTI-LOOP compensation allows the transient ■ Adjustable Soft-Start Current Ramping response to be optimized over a wide range of output ■ Latched Short-Circuit Shutdown with Defeat Option capacitance and ESR values. A RUN/SS pin for each ■ Remote Output Voltage Sense and OV Protection controller provides both soft-start and an optional timed, ■ 5V and 3.3V Standby Regulators short-circuit shutdown that can be configured to latch off ■ Selectable Const. Freq. or Burst ModeTM Operation one or both controllers. Current foldback provides
Step-Up Regulator
additional short-circuit protection. In an overvoltage ■
High Operating Switching Frequency of 1.2MHz
condition, the bottom MOSFET is latched on until VOUT ■
Low Internal V
returns to normal. The FCB pin can be used to inhibit Burst
CESAT Switch: 400mV @ 1A, VIN = 3V
■ Wide
V Mode operation or to enable regulation of a secondary IN Range: 2.6V to 16V Operation ■ output voltage. High Output Voltage: Up to 34V
U APPLICATIO S
The step-up regulator operates at 1.2MHz, allowing the use of tiny low cost capacitors and inductors. In addition, ■ 3.3V Input Step-Down Converter its internal 1A switch allows high current outputs to be ■ Notebook and Palmtop Computers, PDAs generated. Its current mode control scheme provides ■ excellent line and load regulation. Battery-Operated Digital Devices , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation.
U TYPICAL APPLICATIO
V 10µH IN 5.2V 33µF + 10µF TO 28V + 35V 35V 1µF 4.7µF VOUT3 ALUM CER CER 10V 12V INTV AUXV CC IN VIN + 200mA M3 TG2 TG1 M1 10µF 0.1µF 0.1µF 20V 6.3µH BOOST2 BOOST1 SW2 SW1 6.8µH LTC1876 M4 BG2 BG1 M2 AUXSW PGND AUXVFB PGOOD AUXSD 86.6k, 1% SENSE2+ SENSE1+ 0.01Ω 1000pF 1000pF 0.01Ω V SENSE2– SENSE1– V OUT2 OUT1 3.3V 5V V 5A OSENSE2 VOSENSE1 4A 63.4k 105k 1% + ITH2 ITH1 56µF 1% + 47µF 220pF 4V RUN/SS2 SGND RUN/SS1 220pF 20k 6.3V 10.2k 20k SP 1% SP 1% 1% 15k 15k 0.1µF 0.1µF M1, M2, M3, M4: FDS6680A 1876 TA01
Figure 1. High Efficiency Triple 5V/3.3V/12V Power Supply
1876fa 1
U FEATURES DESCRIPTIO Step-Down Controller
The LTC®1876 is a high performance triple output switching ■
Out-of-Phase Controllers Reduce Required Input
regulator. It incorporates a dual step-down switching con-
Capacitance and Power Supply Induced Noise
troller that drives all N-channel synchronous power MOSFET ■
Power Good Output Voltage Indicator
stages. A step-up regulator with an internal 1A, 36V switch ■ OPTI-LOOPTM Compensation Minimizes C provides the third output. OUT ■ DC Programmed Fixed Frequency 150kHz to 300kHz The step-down controllers minimize power loss and noise ■ Wide VIN Range: 3.5V to 36V Operation by operating the output stage of each controller out of ■ Very Low Dropout Operation: 99% Duty Cycle phase. OPTI-LOOP compensation allows the transient ■ Adjustable Soft-Start Current Ramping response to be optimized over a wide range of output ■ Latched Short-Circuit Shutdown with Defeat Option capacitance and ESR values. A RUN/SS pin for each ■ Remote Output Voltage Sense and OV Protection controller provides both soft-start and an optional timed, ■ 5V and 3.3V Standby Regulators short-circuit shutdown that can be configured to latch off ■ Selectable Const. Freq. or Burst ModeTM Operation one or both controllers. Current foldback provides
Step-Up Regulator
additional short-circuit protection. In an overvoltage ■
High Operating Switching Frequency of 1.2MHz
condition, the bottom MOSFET is latched on until VOUT ■
Low Internal V
returns to normal. The FCB pin can be used to inhibit Burst
CESAT Switch: 400mV @ 1A, VIN = 3V
■ Wide
V Mode operation or to enable regulation of a secondary IN Range: 2.6V to 16V Operation ■ output voltage. High Output Voltage: Up to 34V
U APPLICATIO S
The step-up regulator operates at 1.2MHz, allowing the use of tiny low cost capacitors and inductors. In addition, ■ 3.3V Input Step-Down Converter its internal 1A switch allows high current outputs to be ■ Notebook and Palmtop Computers, PDAs generated. Its current mode control scheme provides ■ excellent line and load regulation. Battery-Operated Digital Devices , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation.
U TYPICAL APPLICATIO
V 10µH IN 5.2V 33µF + 10µF TO 28V + 35V 35V 1µF 4.7µF VOUT3 ALUM CER CER 10V 12V INTV AUXV CC IN VIN + 200mA M3 TG2 TG1 M1 10µF 0.1µF 0.1µF 20V 6.3µH BOOST2 BOOST1 SW2 SW1 6.8µH LTC1876 M4 BG2 BG1 M2 AUXSW PGND AUXVFB PGOOD AUXSD 86.6k, 1% SENSE2+ SENSE1+ 0.01Ω 1000pF 1000pF 0.01Ω V SENSE2– SENSE1– V OUT2 OUT1 3.3V 5V V 5A OSENSE2 VOSENSE1 4A 63.4k 105k 1% + ITH2 ITH1 56µF 1% + 47µF 220pF 4V RUN/SS2 SGND RUN/SS1 220pF 20k 6.3V 10.2k 20k SP 1% SP 1% 1% 15k 15k 0.1µF 0.1µF M1, M2, M3, M4: FDS6680A 1876 TA01
Figure 1. High Efficiency Triple 5V/3.3V/12V Power Supply
1876fa 1
