DocumentationDatasheet
Application Note
Reliability Data
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Features
- Operates with Power Blocks, DrMOS or External Gate Drivers and MOSFETs
- Constant-Frequency Voltage Mode Control with Accurate Current Sharing
- ±0.75% 0.6V Voltage Reference
- Differential Remote Output Voltage Sense Amplifier
- Multiphase Capability—Up to 12-Phase Operation
- Programmable Current Limit
- Safely Powers a Prebiased Load
- Programmable or PLL-Synchronizable Switching Frequency Up to 2.25MHz
- Lossless Current Sensing Using Inductor DCR or Precision Current Sensing with Sense Resistor
- VCC Range: 3V to 5.5V
- VIN Range: 3V to 24V
- Power Good Output Voltage Monitor
- Output Voltage Tracking Capability
- Programmable Soft-Start
- Available in a 32-Pin 5mm × 5mm QFN Package
Typical Application
Description
The LTC®3861-1 is a dual PolyPhase® synchronous stepdown switching regulator controller for high current distributed power systems, digital signal processors, and other telecom and industrial DC/DC power supplies. It uses a constant-frequency voltage mode architecture combined with very low offset, high bandwidth error amplifiers and a remote output sense differential amplifier for excellent transient response and output regulation.
The controller incorporates lossless inductor DCR current sensing to maintain current balance between phases and to provide overcurrent protection. The chip operates from a VCC supply between 3V and 5.5V and is designed for stepdown conversion from VIN between 3V and 24V to output voltages between 0.6V and VCC – 0.5V.
Inductor current reversal is disabled during soft-start to safely power prebiased loads. The constant operating frequency can be synchronized to an external clock or linearly programmed from 250kHz to 2.25MHz. Up to six LTC3861-1 controllers can operate in parallel for 1-, 2-, 3-, 4-, 6- or 12-phase operation.
The LTC3861-1 is pin-to-pin compatible with the LTC3860. It is available in a 32-pin 5mm × 5mm QFN package. The LTC3861is a 36-pin QFN version of the LTC3861-1, which has dual differential output voltage sense amplifiers.
| # Diff Amps |
Config Pin | Package | |
| LTC3861 | 2 | Yes | 5 x 6 QFN-36 |
| LTC3861-1 | 1 | No | 5 x 5 QFN-32 |
5x5 QFN-32
Package Variations and Pricing
| Part Number | Package | Pins | Temp | Price (1-99) |
Price (1k)* |
|---|---|---|---|---|---|
| LTC3861EUH-1#PBF | QFN | 32 | E | $3.94 | $2.76 |
| LTC3861EUH-1#TRPBF | QFN | 32 | E | $2.82 | |
| LTC3861EUHE#PBF | QFN | 36 | E | $4.11 | $2.88 |
| LTC3861EUHE#TRPBF | QFN | 36 | E | $2.94 | |
| LTC3861IUH-1#PBF | QFN | 32 | I | $4.37 | $3.06 |
| LTC3861IUH-1#TRPBF | QFN | 32 | I | $3.12 | |
| LTC3861IUHE#PBF | QFN | 36 | I | $4.54 | $3.18 |
| LTC3861IUHE#TRPBF | QFN | 36 | I | $3.24 |
Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.