LM5069 datasheet(19/28 Pages) TI

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R4 =

(VOVH - 2.5V)

2.5V x R3

R3 =

VOVH - VOVL

21 PA

VOV(HYS)

21 PA

R2 =

(VUVL - 2.5V)

2.5V x R1

R1 =

VUVH - VUVL

21 PA

VUV(HYS)

21 PA

VIN

UVLO

OVLO

GND

TIMER AND GATE

LOGIC CONTROL

LM5069

21 PA

2.5V

VSYS

VOVL = [(R1 + R2) x (2.5V) - 21 PA)] + 2.5V

VOVH =

2.5V x (R1 + R2 + R3)

VUVL =

2.5V x (R1 + R2 + R3)

R2 + R3

VUVH = 2.5V + [R1 x (21 PA +

(R2 + R3)

2.5V

)]

R2 =

2.5V x 190.5 k:

(32V - 2.5V)

- 8.61 k: = 7.53 k:

LM5069

www.ti.com

SNVS452D – SEPTEMBER 2006 – REVISED MAY 2013

The lower OVLO threshold calculates to 55.8V, and the OVLO hysteresis is 4.2V. Note that the OVLO hysteresis

is always slightly greater than the UVLO hysteresis in this configuration. When the R1-R3 resistor values are

known, the threshold voltages and hysteresis are calculated from the following:

VUV(HYS) = R1 x 21 µA

VOV(HYS) = (R1 + R2) x 21 µA

Option B: If all four thresholds must be accurately defined, the configuration in Figure 34 can be used.

Figure 34. Programming the Four Thresholds

The four resistor values are calculated as follows:

- Choose the upper and lower UVLO thresholds (VUVH) and (VUVL).

-Choose the upper and lower OVLO threshold (VOVH) and (VOVL).

As an example, assume the application requires the following thresholds: VUVH = 22V, VUVL = 17V, VOVH = 60V,

and VOVL = 58V. Therefore VUV(HYS) = 5V, and VOV(HYS) = 2V. The resistor values are:

R1 = 238 k

Ω, R2 = 41 kΩ

R3 = 95.2 k

Ω, R4 = 4.14 kΩ

Where the R1-R4 resistor values are known, the threshold voltages and hysteresis are calculated from the

following:

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