The LM5149 is a 80-V, ultra-low IQ 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 VIN 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.
PART NUMBER | PACKAGE(1) | BODY SIZE (NOM) |
---|---|---|
LM5149 | RGY (VQFN, 24) | 3.50 mm × 5.50 mm |
Changes from Revision * (December 2020) to Revision A (January 2023)
Additional features of the LM5149 include 150°C maximum junction temperature operation, user-selectable diode emulation for lower current consumption at light-load conditions, open-drain power-good flag for fault reporting and output monitoring, precision enable input, monotonic start-up into prebiased load, integrated VCC bias supply regulator and bootstrap diode, internal 3-ms soft-start time, and thermal shutdown protection with automatic recovery.
The LM5149- controller comes in a 3.5-mm × 5.5-mm thermally enhanced, 24-pin VQFN package with an exposed pad to aid in thermal dissapation.
PIN | I/O(1) | DESCRIPTION | |
---|---|---|---|
NO. | NAME | ||
1 | AVSS | G | Active EMI bias ground connection |
2 | INJ | O | Active EMI injection output |
3 | CNFG | 1 | Connect a resistor to ground to set primary/secondary, spread spectrum enable/disable, or interleaved operation. After start-up, use CNFG to enable AEF. |
4 | RT | I | Frequency programming pin. A resistor from RT to AGND sets the oscillator frequency between 100 kHz and 2.2 MHz. |
5 | EXTCOMP | O | The output of the transconductance error amplifier. If used, connect the compensation network from EXTCOMP to AGND. |
6 | FB | I | Connect FB to VDDA to set the output voltage to 3.3 V. Connect FB using a 24.9 kΩ or 49.9 kΩ to VDDA to set the output voltage to 5 V or 12 V, respectively. Install a resistor divider from VOUT to AGND to set the output voltage setpoint between 0.8 V and 55 V. The regulation voltage at FB is 0.8 V. |
7 | AGND | G | Analog ground connection. Ground return for the internal voltage reference and analog circuits. |
8 | VDDA | O | Internal analog bias regulator. Connect a ceramic decoupling capacitor from VDDA to AGND. |
9 | VCC | P | VCC bias supply pin. Connect ceramic capacitors between VCC and PGND. |
10 | PGND | G | Power ground connection pin for low-side power MOSEFT gate driver |
11 | LO | O | Low-side power MOSFET gate driver output |
12 | VIN | P | Supply voltage input source for the VCC regulators |
13 | HO | O | High-side power MOSFET gate driver output |
14 | SW | P | Switching node of the buck regulator and high-side gate driver return. Connect to the bootstrap capacitor, the source terminal of the high-side MOSFET, and the drain terminal of the low-side MOSFET. |
15 | CBOOT | P | High-side driver supply for bootstrap gate drive |
16 | VCCX | P | Optional input for an external bias supply. If VVCCX > 4.3 V, VCCX is internally connected to VCC and the internal VCC regulator is disabled. |
17 | PG/SYNCOUT | P | An open-collector output that goes low if VOUT is outside the specified regulation window. The PG/SYNCOUT pin of the primary controller in dual-phase mode provides a 180° phase-shifted SYNCOUT signal. |
18 | PFM/SYNC | I | Connect PFM/SYNC to VDDA to enable diode emulation mode. Connect PFM to GND to operate the LM5149 in forced PWM (FPWM) mode with continuous conduction at light loads. PFM/SYNC can also be used as a synchronization input to synchronize the internal oscillator to an external clock. |
19 | EN | I | An active-high precision input with rising threshold of 1 V and hysteresis current of 10 µA. If the EN voltage is less than 0.5 V, the LM5149 is in shutdown mode, unless a SYNC signal is present on PFM/SYNC. |
20 | ISNS+ | I | Current sense amplifier input. Connect the ISNS+ to the inductor side of the external current sense resistor (or to the relevant sense capacitor terminal if inductor DCR current sensing is used) using a Kelvin connection. |
21 | VOUT | I | Output voltage sense and the current sense amplifier input. Connect VOUT to the output side of the current sense resistor (or to the relevant sense capacitor terminal if inductor DCR current sensing is used). |
22 | AEFVDDA | P | Active EMI bias power. Connect a ceramic capacitor between AEFVDDA and AVSS. |
23 | SENSE | I | Active EMI sense input |
24 | REFAGND | G | Active EMI reference ground |