SNVSC55 September 2025 LM51770-Q1
PRODUCTION DATA
- 1
- 1 Features
- 2 Applications
- 3 Description
- 4 Device Comparison
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Parameter Measurement Information
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3
Feature Description
- 8.3.1 Power-On Reset (POR System)
- 8.3.2 Buck-Boost Control Scheme
- 8.3.3 Power Save Mode
- 8.3.4 Supply Voltage Selection – VMAX Switch
- 8.3.5 Enable and Undervoltage Lockout
- 8.3.6 Oscillator Frequency Selection
- 8.3.7 Frequency Synchronization
- 8.3.8 Voltage Regulation Loop
- 8.3.9 Output Voltage Tracking
- 8.3.10 Slope Compensation
- 8.3.11 Configurable Soft Start
- 8.3.12 Peak Current Sensor
- 8.3.13 Current Monitoring and Current Limit Control Loop
- 8.3.14 Short Circuit - Hiccup Protection
- 8.3.15 nFLT Pin and Protections
- 8.3.16 Device Configuration Pin
- 8.3.17 Dual Random Spread Spectrum – DRSS
- 8.3.18 Gate Driver
- 8.4 Device Functional Modes
-
9 Application and Implementation
- 9.1 Application Information
- 9.2
Typical Application
- 9.2.1 Design Requirements
- 9.2.2
Detailed Design Procedure
- 9.2.2.1 Custom Design with WEBENCH Tools
- 9.2.2.2 Frequency
- 9.2.2.3 Feedback Divider
- 9.2.2.4 Inductor and Current Sense Resistor Selection
- 9.2.2.5 Slope Compensation
- 9.2.2.6 Output Capacitor
- 9.2.2.7 Input Capacitor
- 9.2.2.8 UVLO Divider
- 9.2.2.9 Soft-Start Capacitor
- 9.2.2.10 MOSFETs QH1 and QL1
- 9.2.2.11 MOSFETs QH2 and QL2
- 9.2.2.12 Output Voltage Frequency Compensation
- 9.2.2.13 External Component Selection
- 9.2.3 Application Curves
- 9.3 System Examples
- 9.4 Power Supply Recommendations
- 9.5 Layout
- 10Device and Documentation Support
- 11Revision History
- 12Mechanical, Packaging, and Orderable Information
Package Options
Refer to the PDF data sheet for device specific package drawings
Mechanical Data (Package|Pins)
- DCP|38
Thermal pad, mechanical data (Package|Pins)
Orderable Information
6.7 Typical Characteristics
The following conditions apply (unless otherwise noted): TJ = 25°C; V(VCC) = 5V
Figure 6-1 Switching Frequency Versus RT Resistance
Figure 6-3 VIN LDO - VCC Voltage
versus VCC Load Current
Figure 6-5 BIAS LDO - VCC Voltage
versus VCC Load Current
Figure 6-7 FB Pin Reference Voltage
versus Temperature
Figure 6-9 CSA Input Current versus
Temperature 
Figure 6-11 Minimum Controllable
On-time versus Switching Frequency
Figure 6-13 UVLO Threshold Voltage
versus Temperature 
Figure 6-15 Shutdown Current into VIN
versus TemperatureVEN/UVLO = 0V ,V(VIN) = 12V, V(BIAS) = 0V
Figure 6-17 Shutdown Current into BIAS
versus Temperature VEN/UVLO = 0V ,V(BIAS) = 12V, V(VIN) = 3.5V
Figure 6-19 Quiescent Current into
BIAS versus Pin Voltage VEN/UVLO = 3.3V, V(BIAS) = 12V, V(VIN) = 3.5 V
Figure 6-21 Soft-Start current versus
Temperature Figure 6-2 Switching Frequency Versus
Temperature R(RT) = 75kΩ
Figure 6-4 VIN LDO - VCC Voltage
versus VIN Voltage I(VCC) = 20mA
Figure 6-6 BIAS LDO - VCC Voltage
versus BIAS Voltage I(VCC) = 50mA
Figure 6-8 Current Limit Threshold
Voltage Versus Temperature
Figure 6-10 CSB Input Current versus
Temperature 
Figure 6-12 Minimum Controllable
Off-time versus Switching Frequency
Figure 6-14 Shutdown Current into VIN
versus Pin Voltage VEN/UVLO = 0V ,V(VIN) = 12V, V(BIAS) = 0V
Figure 6-16 Shutdown Current into BIAS
versus Pin Voltage VEN/UVLO = 0V ,V(BIAS) = 12V, V(VIN) = 3.5V
Figure 6-18 Standby Current into VIN
versus Temperature VEN/UVLO = 0.8V, V(VIN) = 12V, V(BIAS) = 0V
Figure 6-20 Quiescent Current into
BIAS versus Temperature VEN/UVLO = 3.3V, V(BIAS) = 12V, V(VIN) = 3.5V
Figure 6-22 Hysteresis Current on
EN/UVLO versus Temperature