Current Limit

Detect

Control Logic

Soft

start

Thermal

Shutdown

UVLO

GM

Gate Drive

VIN

GND

FB

Vref

EN

SW

+

_

DBG

DBG

PMOS

NMOS

Valley

Current

Detect

Pulse

Modulator

Duty Detect

SW

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7

TLV62565, TLV62566

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SLVSBC1D – OCTOBER 2013 – REVISED OCTOBER 2016

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9 Detailed Description

9.1 Overview

The TLV62565/6 device family includes two high-efficiency synchronous step-down converters. Each device

operates with an adaptive on-time control scheme, which is able to dynamically adjust the on-time duration

based on the input voltage and output voltage so that it can achieve relative constant frequency operation. The

device operates at typically 1.5-MHz frequency pulse width modulation (PWM) at moderate to heavy load

currents. Based on the VIN/VOUT ratio, a simple circuit sets the required on time for the high-side MOSFET. It

makes the switching frequency relatively constant regardless of the variation of input voltage, output voltage, and

load current. At the beginning of each switching cycle, the high-side switch is turned on and the inductor current

ramps up to a peak current that is defined by on time and inductance. In the second phase, once the on time

expires, the high-side switch is turned off while the low-side switch is turned on. The current through the inductor

then decays until triggering the valley current level determined by the output of the error amplifier. Once this

occurs, the on timer is set to turn the high-side switch back on again and the cycle is repeated.

The TLV62565/6 device family offers excellent load transient response with a unique fast response constant on-

time valley current mode. The switching frequency changes during load transition so that the output voltage

comes back in regulation faster than a traditional fixed PWM control scheme. Internal loop compensation is

integrated which simplifies the design process while minimizing the number of external components. At light load

currents the device automatically operates in Power Save Mode with pulse frequency modulation (PFM).

9.2 Functional Block Diagrams

Figure 4. TLV62565 Functional Block Diagram