VBIAS

PH

BOOT

VIN

LSG

VBIAS

Error

Amplifier

2x Oscillator

PWM Ramp

(FeedFoward)

SYNC

RT

VSENSE

PWM

Comparator

Reference

System

ENA

VBIAS2

Hiccup

Timer

Thermal

Shutdown

Current Limit

Hiccup

Hiccup

UVLO

UVLO

UVLO

1.2V

Bias + Drive

Regulator

PWRGD

AGND

PGND

Rising

Edge

Delay

VBIAS

COMP

Adaptive Deadtime

and

Control Logic

97% Ref

POWERPAD

VSENSE

UVLO

S

R

Q

320 k

Ω

125 k

5

µA

Z3

Z1

Z2

Z5

Z4

TPS5435x

DETAILED DESCRIPTION

Undervoltage Lockout (UVLO)

R1 +

VIN(start)

1 kW

1.24 V

* 1 kW

(1)

VIN(stop) +

(R1 ) 1 kW)

1.02 V

1 kW

(2)

TPS54352-EP

,, TPS54353-EP,, TPS54354-EP

TPS54355-EP

, TPS54356-EP, TPS54357-EP

FUNCTIONAL BLOCK DIAGRAM

The UVLO system has an internal voltage divider from VIN to AGND. The defaults for the start/stop values are

labeled VIN and are given in Table 1. The internal UVLO threshold can be overridden by placing an external

resistor divider from VIN to ground. The internal divider values are approximately 320 k

Ω for the high-side

resistor and 125 k

Ω for the low-side resistor. The divider ratio (and, therefore, the default start/stop values) is

quite accurate, but the absolute values of the internal resistors may vary as much as 15%. If high accuracy is

required for an externally adjusted UVLO threshold, select lower-value external resistors to set the UVLO

threshold. Using a 1-k

Ω resistor for the low-side resistor (R2 see Figure 1) is recommended. Under no

circumstances should the UVLO pin be connected directly to VIN.

Table 1. Start/Stop Voltage Threshold

START VOLTAGE THRESHOLD

STOP VOLTAGE THRESHOLD

TPS54352-6

4.49

3.69

VIN (default)

TPS54357

6.65

5.45

UVLO

1.24

1.02

The equations for selecting the UVLO resistors are:

8

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