LM5149 80-V, Synchronous, Buck, DC/DC Controller with Ultra-Low IQ and Integrated Active EMI Filter

1 Features

Functional Safety-Capable
- Documentation available to aid functional safety system design
Two integrated EMI mitigation mechanisms
- Active EMI Filter for enhanced EMI performance at lower frequencies
- Selectable dual random spread spectrum (DRSS) for enhanced EMI performance across low and high-frequency bands
- EMI reduced by an average of 25 dBµV
- Reduces the external differential-mode input filter size by 50% and lowers systems cost
- Optimized for CISPR 32 Class B requirements
Versatile synchronous buck DC/DC controller
- Wide input voltage range of 3.5 V to 80 V
- 1% accurate, fixed 3.3 V, 5 V, 12 V, or adjustable output from 0.8 V to 55 V
- 150°C maximum junction temperature
- Shutdown mode current: 2.3 µA
- No-load sleep current: 9.5 µA
- Stackable up to two phases
- Advanced dropout with frequency foldback
Switching frequency from 100 kHz to 2.2 MHz
- SYNC in and SYNC out capability
Inherent protection features for robust design
- Internal hiccup-mode overcurrent protection
- ENABLE and PGOOD functions
- VCC, VDDA, and gate-drive UVLO protection
- Internal or external loop compensation
- Thermal shutdown protection with hysteresis
Create a custom design using the LM5149 with WEBENCH® Power Designer

2 Applications

3 Description

The LM5149 is a 80-V, ultra-low I_Q synchronous buck DC/DC controller for high-current, single-output applications. The controller uses a peak current-mode control architecture for easy loop compensation, fast transient response, and excellent load and line regulation. The LM5149 can be set up in interleaved dual-phase mode with accurate current sharing for high-current applications. The device can operate with V_IN as low as 3.5 V, at nearly 100% duty cycle if needed.

The LM5149 has two unique EMI reduction features: active EMI filter and dual random spread spectrum (DRSS). The active EMI filter senses any noise or ripple voltage on the DC input bus and injects an out-of-phase cancellation signal to reduce the disturbance. DRSS combines low-frequency triangular and high-frequency randomized modulations to mitigate EMI across lower and higher frequency bands, respectively. This hybrid technique aligns with the multiple resolution bandwidth (RBW) settings specified in industry-standard EMC tests.

Package Information

PART NUMBER	PACKAGE⁽¹⁾	BODY SIZE (NOM)
LM5149	RGY (VQFN, 24)	3.50 mm × 5.50 mm

(1) For all available packages, see the orderable addendum at the end of the data sheet

Typical Application Schematic

CISPR 25 EMI Performance - 150 kHz to 30 MHz