(nF) x VFB(V)

(nF) x 0.773 V

SS

SS

t

(ms) =

=

SS

I

( A)

SS

C

C

6.4 A

m

m

(

)

IN

OUT

OUT

OUT(LL)

SW

IN

V -V

×V

1

I

=

×

2×L×f

V

13

TPS53014

www.ti.com

SLVSBF1A – MAY 2012 – REVISED FEBRUARY 2019

Product Folder Links: TPS53014

Submit Documentation Feedback

Copyright © 2012–2019, Texas Instruments Incorporated

Feature Description (continued)

7.3.2 Auto-Skip Eco-Mode™ Control

The TPS53014 is designed with Auto-Skip Eco-mode™ to increase light load efficiency. As the output current

decreases from heavy load condition, the inductor current is also reduced and eventually comes to point where

its rippled valley touches zero level, which is the boundary between continuous conduction and discontinuous

conduction modes. The rectifying MOSFET is turned off when its zero inductor current is detected. As the load

current further decreases the converter run into discontinuous conduction mode. The on-time is kept almost half

as is was in the continuous conduction mode because it takes longer time to discharge the output capacitor with

smaller load current to the level of the reference voltage. The transition point to the light load operation IOX(LL)

current can be calculated in Equation 1 with 500kHz used as fsw.

(1)

7.3.3 Drivers

TPS53014 contains two high-current resistive MOSFET gate drivers. The low-side driver is a PGND referenced,

VREG5 powered driver designed to drive the gate of a high-current, low RDS(on) N-channel MOSFET whose

source is connected to PGND. The high-side driver is a floating SW referenced, VBST powered driver designed

to drive the gate of a high-current, low RDS(on) N-channel MOSFET. To maintain the VBST voltage during the

high-side driver ON time, a capacitor is placed from SW to VBST. Each driver draws average current equal to

Gate Charge (Qg @ Vgs = 5V) times Switching frequency (fsw). To prevent cross-conduction, there is a narrow

dead-time when both high-side and low-side drivers are OFF between each driver transition. During this time the

inductor current is carried by one of the MOSFETs body diodes.

7.3.4 5-Volt Regulator

The TPS53014 has an internal 5V Low-Dropout (LDO) Regulator to provide a regulated voltage for all both

drivers and the ICs internal logic. A high-quality 4.7µF or greater ceramic capacitor from VREG5 to GND is

required to stabilize the internal regulator.

7.3.5 Soft Start and Pre-Biased Soft Start

The soft start function is adjustable. When the EN pin becomes high, 6.4-µA current begins charging the

capacitor which is connected from the SS pin to GND. Smooth control of the output voltage is maintained during

start up. The equation for the slow start time is shown in Equation 2. VFB voltage is 0.773 V and SS pin source

current is 6.4-µA.

(2)

The TPS53014 contains a unique circuit to prevent current from being pulled from the output during startup if the

output is pre-biased. When the soft-start commands a voltage higher than the pre-bias level (internal soft start

becomes greater than internal feedback voltage VFB), the controller slowly activates synchronous rectification by

starting the first low side FET gate driver pulses with a narrow on-time. It then increments that on-time on a

cycle-by-cycle basis until it coincides with the time dictated by (1-D), where D is the duty cycle of the converter.

This scheme prevents the initial sinking of the pre-biased output, and ensures that the output voltage (VO) starts

and ramps up smoothly into regulation from pre-biased startup to normal mode operation.

7.3.6 Overcurrent Protection

TPS53014 has a cycle-by-cycle over current limit feature. The over current limits the inductor valley current by

monitoring the voltage drop across the low-side MOSFET RDS(on) during the low-side driver on-time. If the

inductor current is larger than the over current limit (OCL), the TPS53014 delays the start of the next switching

cycle until the sensed inductor current falls below the OCL current. MOSFET RDS(on) current sensing is used to

provide an accuracy and cost effective solution without external devices. To program the OCL, a resister should

be connected between DRVL and PGND. The recommended values are given inTable 1.