MAX797
Step-Down Controllers with Synchronous Rectifier for CPU Power
We Recommend Improved Performance Devices: MAX1652/MAX1653/MAX1654/MAX1655 for New Designs
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The MAX796/MAX799 are specially equipped with a secondary feedback input (SECFB) for transformer-based dual-output applications. This secondary feedback path improves cross-regulation of positive (MAX796) or negative (MAX799) auxiliary outputs.
The MAX797 has a logic-controlled and synchronizable fixed-frequency pulse-width-modulating (PWM) operating mode, which reduces noise and RF interference in sensitive mobile-communications and pen-entry applications. The SKIP-bar override input allows automatic switchover to idle-mode operation (for high-efficiency pulse skipping) at light loads, or forces fixed-frequency mode for lowest noise at all loads.
The MAX796/MAX797/MAX799 are all available in 16-pin DIP and narrow SO packages. See the table below to compare these three converters.
Key Features
- 96% Efficiency
- 4.5V to 30V Input Range
- 2.5V to 6V Adjustable Output
- Preset 3.3V and 5V Outputs (at up to 10A)
- Multiple Regulated Outputs
- +5V Linear-Regulator Output
- Precision 2.505V Reference Output
- Automatic Bootstrap Circuit
- 150kHz/300kHz Fixed-Frequency PWM Operation
- Programmable Soft-Start
- 375µA Typ Quiescent Current (VIN = 12V, VOUT = 5V)
- 1µA Typ Shutdown Current
Applications/Uses
- Cell Phones
- Notebook and Subnotebook Computers
- PDAs and Mobile Communicators
| VIN (V) (min) | 4.5 |
| VIN (V) (max) | 30 |
| VOUT1 (V) (min) | 2.5 |
| VOUT1 (V) (max) | 6 |
| IOUT1 (A) (max) | 10 |
| Switch Type | External |
| Preset VOUT (V) | 5 |
| Output Adjust. Method | Preset Resistor |
| Synchronous Switching? | Yes |
| # DC-DC Outputs | 1 |
| Switching Frequency (kHz) | 340 |
| Package/Pins | SOIC (N)/16 |
| Budgetary Price (See Notes) | $5.85 @1k |
Technical Docs
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Description
The MAX797 evaluation kit (EV kit) is a preassembled and tested demonstration board that embodies the standard 3.3V application circuit. The board comes configured to accept battery voltages between 4.5V and 28V, but can be reconfigured for voltages between 4.5V and 30V by substituting MOSFETs with higher breakdown voltage ratings.
The standard board is guaranteed to deliver at least 3A of load current. To modify the load-current capability, change the sense-resistor (R1) value and re-size the external components according to Table 1 in the MAX796/MAX797/MAX799 data sheet.
The main output voltage comes preset to 3.35V (nominal). To select 5V operation, move jumper J3 to position 1-2. For operation in adjustable mode, install resistors R4 & R5 and remove the jumper. There is a small PC trace jumper that shunts J3 on the board. This default jumper must be cut apart for either adjustable-mode or fixed 5V operation. Don't operate the circuit if a jumper or resistor divider has not been installed, as this will damage the IC due to output overvoltage.
In addition to the standard components, the EV kit has some extra pull-up and pull-down resistors (R4-R8) to set default logic input levels. These resistors can usually be omitted in the final design.
Features
- Battery Range: 4.5V to 28V
- Load Capability: 3.3V at 3A
- Adjustable 2.5V to 6V Output (optional resistor divider)
- Precision 2.505V Reference Output
- Oscillator SYNC Input
- Low-Noise Mode Control Input
Support & Training
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Filtered SearchOur dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal
Parameters
| VIN (V) (min) | 4.5 |
| VIN (V) (max) | 30 |
| VOUT1 (V) (min) | 2.5 |
| VOUT1 (V) (max) | 6 |
| IOUT1 (A) (max) | 10 |
| Switch Type | External |
| Preset VOUT (V) | 5 |
| Output Adjust. Method | Preset Resistor |
| Synchronous Switching? | Yes |
| # DC-DC Outputs | 1 |
| Switching Frequency (kHz) | 340 |
| Package/Pins | SOIC (N)/16 |
| Budgetary Price (See Notes) | $5.85 @1k |
Key Features
- 96% Efficiency
- 4.5V to 30V Input Range
- 2.5V to 6V Adjustable Output
- Preset 3.3V and 5V Outputs (at up to 10A)
- Multiple Regulated Outputs
- +5V Linear-Regulator Output
- Precision 2.505V Reference Output
- Automatic Bootstrap Circuit
- 150kHz/300kHz Fixed-Frequency PWM Operation
- Programmable Soft-Start
- 375µA Typ Quiescent Current (VIN = 12V, VOUT = 5V)
- 1µA Typ Shutdown Current
Applications/Uses
- Cell Phones
- Notebook and Subnotebook Computers
- PDAs and Mobile Communicators
Description
The MAX796/MAX799 are specially equipped with a secondary feedback input (SECFB) for transformer-based dual-output applications. This secondary feedback path improves cross-regulation of positive (MAX796) or negative (MAX799) auxiliary outputs.
The MAX797 has a logic-controlled and synchronizable fixed-frequency pulse-width-modulating (PWM) operating mode, which reduces noise and RF interference in sensitive mobile-communications and pen-entry applications. The SKIP-bar override input allows automatic switchover to idle-mode operation (for high-efficiency pulse skipping) at light loads, or forces fixed-frequency mode for lowest noise at all loads.
The MAX796/MAX797/MAX799 are all available in 16-pin DIP and narrow SO packages. See the table below to compare these three converters.
Technical Docs
Support & Training
Search our knowledge base for answers to your technical questions.
Filtered SearchOur dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal
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