The LM5576 is an easy to use SIMPLE SWITCHER® buck regulator which allows design engineers to design and optimize a robust power supply using a minimum set of components. Operating with an input voltage range of 6 - 75 V, the LM5576 delivers 3 A of continuous output current with an integrated 170 mΩ N-Channel MOSFET. The regulator utilizes an Emulated Current Mode architecture which provides inherent line regulation, tight load transient response, and ease of loop compensation without the usual limitation of low-duty cycles associated with current mode regulators. The operating frequency is adjustable from 50 kHz to 500 kHz to allow optimization of size and efficiency. To reduce EMI, a frequency synchronization pin allows multiple ICs from the LM(2)557x family to self-synchronize or to synchronize to an external clock. The LM5576 ensures robustness with cycle-by-cycle current limit, short-circuit protection, thermal shut-down, and remote shut-down. The device is available in a power enhanced HTSSOP-20 package featuring an exposed die attach pad for thermal dissipation. The LM5576 is supported by the full suite of WEBENCH® On-Line design tools.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM5576 | HTSSOP (20) | 6.50 mm x 4.40 mm |
LM5576-Q1 |
Changes from I Revision (April 2013) to J Revision
Changes from H Revision (April 2013) to I Revision
PIN | I/O | DESCRIPTION | APPLICATION INFORMATION | |
---|---|---|---|---|
NO. | NAME | |||
1 | VCC | O | Output of the bias regulator | VCC tracks VIN up to 9 V. Beyond 9 V, VCC is regulated to 7 Volts. A 0.1-uF to 1-uF ceramic decoupling capacitor is required. An external voltage (7.5 V – 14 V) can be applied to this pin to reduce internal power dissipation. |
2 | SD | I | Shutdown or UVLO input | If the SD pin voltage is below 0.7 V the regulator will be in a low power state. If the SD pin voltage is between 0.7 V and 1.225 V the regulator will be in standby mode. If the SD pin voltage is above 1.225 V the regulator will be operational. An external voltage divider can be used to set a line undervoltage shutdown threshold. If the SD pin is left open circuit, a 5-µA pull-up current source configures the regulator fully operational. |
3, 4 | VIN | I | Input supply voltage | Nominal operating range: 6 V to 75 V |
5 | SYNC | I | Oscillator synchronization input or output | The internal oscillator can be synchronized to an external clock with an external pull-down device. Multiple LM5576 devices can be synchronized together by connection of their SYNC pins. |
6 | COMP | O | Output of the internal error amplifier | The loop compensation network should be connected between this pin and the FB pin. |
7 | FB | I | Feedback signal from the regulated output | This pin is connected to the inverting input of the internal error amplifier. The regulation threshold is 1.225 V. |
8 | RT | I | Internal oscillator frequency set input | The internal oscillator is set with a single resistor, connected between this pin and the AGND pin. |
9 | RAMP | O | Ramp control signal | An external capacitor connected between this pin and the AGND pin sets the ramp slope used for current mode control. Recommended capacitor range 50 pF to 2000 pF. |
10 | AGND | GROUND | Analog ground | Internal reference for the regulator control functions |
11 | SS | O | Soft-start | An external capacitor and an internal 10-µA current source set the time constant for the rise of the error amp reference. The SS pin is held low during standby, VCC UVLO and thermal shutdown. |
12 | OUT | O | Output voltage connection | Connect directly to the regulated output voltage. |
13, 14 | PGND | GROUND | Power ground | Low side reference for the PRE switch and the IS sense resistor. |
15, 16 | IS | I | Current sense | Current measurement connection for the re-circulating diode. An internal sense resistor and a sample/hold circuit sense the diode current near the conclusion of the off-time. This current measurement provides the DC level of the emulated current ramp. |
17, 18 | SW | O | Switching node | The source terminal of the internal buck switch. The SW pin should be connected to the external Schottky diode and to the buck inductor. |
19 | PRE | I | Pre-charge assist for the bootstrap capacitor | This open drain output can be connected to SW pin to aid charging the bootstrap capacitor during very light load conditions or in applications where the output may be pre-charged before the LM5576 is enabled. An internal pre-charge MOSFET is turned on for 265 ns each cycle just prior to the on-time interval of the buck switch. |
20 | BST | I | Boost input for bootstrap capacitor | An external capacitor is required between the BST and the SW pins. A 0.022-µF ceramic capacitor is recommended. The capacitor is charged from VCCvia an internal diode during the off-time of the buck switch. |
NA | EP | GROUND | Exposed Pad | Exposed metal pad on the underside of the device. It is recommended to connect this pad to the PWB ground plane, in order to aid in heat dissipation. |