LM2745

HG

BOOT

LG

PGND

FB

SD

PWGD

FREQ/SYNC

SS/TRACK

SGND

EAO

PGND

1

2

3

4

5

6

7

8

9

10

11

12

13

14

LM2748

HG

BOOT

LG

PGND

FB

SD

PWGD

FREQ

SS/TRACK

SGND

EAO

PGND

1

2

3

4

5

6

7

8

9

10

11

12

13

14

LM2745, LM2748

SNOSAL2E – APRIL 2005 – REVISED APRIL 2013

www.ti.com

Figure 1. 14-Lead Plastic TSSOP,

Figure 2. 14-Lead Plastic TSSOP,

Top View

Top View

Package Number PW0014A

Package Number PW0014A

Pin Descriptions

BOOT (Pin 1) - Bootstrap pin. This is the supply rail for the high-side gate driver. When the high-side MOSFET turns on, the voltage on this

in the Application Information section for more details on how to select MOSFETs.

LG (Pin 2) - Low-gate drive pin. This is the gate drive for the low-side N-channel MOSFET. This signal is interlocked with the high-side gate

drive HG (Pin 14), so as to avoid shoot-through.

PGND (Pins 3, 13) - Power ground. This is also the ground for the low-side MOSFET driver. Both the pins must be connected together on

the PCB and form a ground plane, which is usually also the system ground.

SGND (Pin 4) - Signal ground. It should be connected appropriately to the ground plane with due regard to good layout practices in

switching power regulator circuits.

source through a pull-up resistor. Choose the pull-up resistor so that the current going into this pin is kept below 1 mA. A recommended

value for the pull-up resistor is 100 k

Ω for most applications. The voltage on this pin is thus pulled low under output undervoltage or

overvoltage fault conditions and also under input UVLO.

between this pin and the drain of the low-side MOSFET (switch node). The minimum value for this resistor is 1 k

Ω.

EAO (Pin 8) - Output of the error amplifier. The voltage level on this pin is compared with an internally generated ramp signal to determine

the duty cycle. This pin is necessary for compensating the control loop.

SS/TRACK (Pin 9) - Soft-start and tracking pin. This pin is internally connected to the non-inverting input of the error amplifier during soft-

start, and in fact any time the SS/TRACK pin voltage happens to be below the internal reference voltage. For the basic soft-start function, a

capacitor of minimum value 1 nF is connected from this pin to ground. To track the rising ramp of another power supply’s output, connect a

resistor divider from the output of that supply to this pin as described in Application Information.

FB (Pin 10) - Feedback pin. This is the inverting input of the error amplifier, which is used for sensing the output voltage and compensating

the control loop.

FREQ/SYNC (Pin 11) - Frequency adjust pin. The switching frequency is set by connecting a resistor of suitable value between this pin and

ground. Some typical values (rounded up to the nearest standard values) are 150 k

Ω for 200 kHz, 100 kΩ for 300 kHz, 51.1 kΩ for 500

kHz, 18.7 k

Ω for 1 MHz. This pin is also used in the LM2745 to synchronize to an external clock.

high-side and low-side drives are off. This pin also features a precision threshold for power supply sequencing purposes, as well as a low

threshold to ensure minimal quiescent current.

HG (Pin 14) - High-gate drive pin. This is the gate drive for the high-side N-channel MOSFET. This signal is interlocked with LG (Pin 2) to

avoid shoot-through.

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

2

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