High Efficiency Linear and Switching Solutions for Splitting a Digital Supply (Design Note 172)
Compare linear (LT1118) and switching (LTC1504) solutions for generating a 2.5V split supply from a 5V rail with source/sink capability and high efficiency.
Overview
This design note details two methods for creating a split supply (virtual ground) from a single 5V digital rail, offering improvements over high-impedance resistor dividers. The first solution utilizes the LT1118-2.5 linear regulator to source up to 800mA and sink up to 400mA with low output noise and 50% power efficiency. The second solution uses the LTC1504 synchronous switching regulator for applications requiring higher efficiency (up to 90%) when sourcing or sinking up to 500mA. The document compares transient response, quiescent current, and thermal performance for both circuits, including component selection for output capacitors and inductors from AVX and Sumida.
Use Cases
- Analog circuitry virtual ground generation
- SCSI termination supplies
- Positive ECL (PECL) supplies
- Battery-powered digital systems
- Low-noise analog subsystem power
Topics
Referenced Parts
CDRH73-220
Sumida
SUMIDA CDRH73-220 (22μH: FAST TRANSIENT RESPONSE)
CDRH73-470
Sumida
L EXT: SUMIDA CDRH73-470 (47μH: LOW RIPPLE, HIGH EFFICIENCY)
LT1118
Linear Technology
The LT1118 is a specialized linear regulator designed to source or sink current
LT1118-2.5
Linear Technology
Figure 2. LT1118-2.5 Supply Splitter
LTC1504
Linear Technology
Figure 5. LTC1504 Supply Splitter
| TAJC476M016R | AVX | COUT: AVX TAJC476M016R |
| CDRH73-220 | Sumida | SUMIDA CDRH73-220 (22μH: FAST TRANSIENT RESPONSE) |
| CDRH73-470 | Sumida | L EXT: SUMIDA CDRH73-470 (47μH: LOW RIPPLE, HIGH EFFICIENCY) |
| LT1118 | Linear Technology | The LT1118 is a specialized linear regulator designed to source or sink current |
| LT1118-2.5 | Linear Technology | Figure 2. LT1118-2.5 Supply Splitter |
| LTC1504 | Linear Technology | Figure 5. LTC1504 Supply Splitter |