Low-Cost, Dual-Output, Step-Down

Controller with Fast Transient Response

6

_______________________________________________________________________________________

Pin Description

PIN

NAME

FUNCTION

1

DH1

High-Side MOSFET Driver Output for Controller 1. Connect DH1 to the gate of the high-side MOSFET. DH1 is

low in shutdown and UVLO.

2

LX1

External Inductor Connection for Controller 1. Connect LX1 to the switching node of the MOSFETs and

inductor. Make sure LX1 is close to the source of the high-side MOSFET(s) to form a Kelvin connection for

high-side current sensing. LX1 is high impedance during monotonic startup and shutdown.

3

BST1

Boost Capacitor Connection for the High-Side MOSFET Driver for Controller 1. Connect a 0.22µF ceramic

capacitor from BST1 to LX1.

4

DL1

Low-Side MOSFET Driver Output for Controller 1. Connect DL1 to the gate of the low-side MOSFET(s) for

controller 1. DL1 is low in shutdown and UVLO.

5VL

Low-Side Gate Drive Supply and Output of the 6.5V Linear Regulator. Connect a 4.7µF ceramic capacitor from

load VL when IC is disabled.

6

PGND

Power Ground. Connect to the power ground plane. Connect power and analog grounds at a single point near

the output capacitor’s ground.

7

DL2

Low-Side MOSFET Driver Output for Controller 2. Connect DL2 to the gate of the low-side MOSFET(s) for

controller 2. DL2 is low in shutdown and UVLO.

8

BST2

Boost Capacitor Connection for the High-Side MOSFET Driver for Controller 2. Connect a 0.22µF ceramic

capacitor from BST2 to LX2.

9

LX2

External Inductor Connection for Controller 2. Connect LX2 to the switching node of the MOSFETs and

inductor. Make sure LX2 is close to the source of the high-side MOSFET(s) to form a Kelvin connection for

high-side current sensing. LX2 is high impedance during monotonic startup and shutdown.

10

DH2

High-Side MOSFET Driver Output for Controller 2. Connect DH2 to the gate of the high-side MOSFET(s) for

controller 2. DH2 is low in shutdown and UVLO.

11

ILIM2

Current-Limit Set for Controller 2. Connect a resistor from the drain of the high-side MOSFET(s) to ILIM2. See

the Setting the Overcurrent Threshold section.

12

FB2

Feedback Input for Controller 2. Connect FB2 to the center of a resistor-divider connected between the output

13

REFIN2

an external reference, connect REFIN2 through a resistor (> 1k

Ω) to a reference voltage between 0V and

1.3V. An RC lowpass filter is recommended when using an external reference and soft-start is not provided by

the external reference. For tracking applications, connect REFIN2 to the center of a resistor voltage-divider

between the output of controller 1 and GND (see Figure 3). Connect REFIN2 to GND to disable controller 2.

14

OSC/EN12

Switching Frequency Set Input. Connect a 22.6k

Ω to 226kΩ resistor from OSC/EN12 to GND to set the

switching frequency between 1000kHz and 100kHz. Connect a switch in series with this resistor for

enable/shutdown control. When the switch is open, the IC enters low-power shutdown mode. In shutdown,

OSC/EN12 is internally driven to approximately 800mV.

15

IN

Internal 6.5V Linear Regulator Input. Connect IN to a 7.2V to 28V supply, and connect a 0.47µF or larger

ceramic capacitor from IN to PGND. When using a 4.5V to 5.5V supply, connect IN to VL.

16

GND

Analog Ground. Connect to the analog ground plane. Connect the analog and power ground planes at a

single point near the output capacitor’s ground.