Table 7-1. SS Pin Strap for the Soft-start Time, Fault Response, and Internal Compensation (continued)

SS Pin to AGND Resistor

(kΩ)

Soft-start time (ms)

Internal Compensation

VOUT OV, UV Fault Response

Floating

4

Compensation1

Latch-off

Note

The pin strap detection happens at the first stage of power-up sequence. After the detection finishes,

the detection results are latched in and do not change during the following operation. If a new

selection is desired, toggling VCC (or AVIN) is required. Toggling the EN pin does not affect the pin

strap detection results.

Shutdown

The TPS548C26 device features a simple shutdown sequence. Both high-side and low-side FET drivers are

turned off immediately at the time when the EN pin is pulled low, and the output voltage discharge slew rate is

controlled by the external load. The internal reference is discharged down to zero to get ready for the next soft

start.

7.3.6 Loop Compensation

The TPS548C26 device features D-CAP+ control topology with internal loop compensation for fast transient

response. As listed in Table 7-1, two sets of loop compensation are provided for tuning the output voltage

feedback and response to transients. Compensation1 is the recommended compensation for any application

using relative large inductor (for example, 400 nH or higher). Compensation2 is the recommended compensation

for any application using relative small inductor (for example, 200 nH or lower). TI does not recommend electing

Compensation2 for a large inductor design because the control loop does not receive the right amount of current

sensing signal when the low-side FET conduction time is approaching tOFF(min).

To avoid wrong pin strap detection, TI recommends ±1% tolerance resistors with a typical temperature coefficient

of ±100 ppm/°C.

7.3.7 Set Switching Frequency and Operation Mode

TPS548C26 device provides programmable operation mode including the forced CCM operation for tight output

voltage ripple and auto-skipping Eco-mode for high light-load efficiency. The TPS548C26 device allows users to

select the switching frequency and operation mode through the pin strap detection on MODE pin. Table 7-2 lists

the resistor values for the switching frequency and operation mode selections. TI recommends ±1% tolerance

resistors with a typical temperature coefficient of ±100 ppm/°C.

The FCCM bit is set during initial power-on and latched after the power conversion is enabled (EN=high). While

the device is enabled, a write to FCCM bit is acknowledged but the operation mode does not change until an EN

toggle happens.

Table 7-2. MODE Pin Strap for Switching Frequency and Operation MODE

MODE Pin to AGND Resistor

(kΩ)

Switching Frequency (kHz)

Operation Mode

0

600

FCCM

1.50

800

2.49

1000

3.48

1200

10.5

600

Auto-skipping Eco-mode (DCM)

12.1

800

14

1000

16.2

1200

Floating

800

FCCM

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TPS548C26

SLVSGM2 – MARCH 2023

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