ISOUSB211DPR datasheet(32/44 Pages) TI

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This configuation offers the lowest power dissipation and the highest ambient temperature operation using

external regulators.

Peripheral

MCU

DGND

0 V

Digital

Ground

ISO

Ground

Galvanic

Isolation Barrier

ISOUSB211

3.3 VLV (local supply)

Upstream

Port

Connector

VCC

VBUS

GND

D-

D+

100 nF

0.1 µF

5 µF

1 µF

0.1 µF

3.3 VLV

VBUS (5.0 V)

LDO/

DC-DC

1.8 V

V3P3V1

VBUS1

VCC1

UD-

UD+

GND1

EQ10

GND1

EQ11

V2OK

V1P8V1

CDPENZ1

V3P3V2

VBUS2

VCC2

DD-

DD+

GND2

V1P8V2

EQ20

GND2

EQ21

V1OK

V1P8V2

V1P8V1

CDPENZ2

3.3 V

LDO/

DC-DC

1.8 VLV

10 nF

0.1 µF

2 µF

10 nF 0.1 µF

2 µF

10 nF 0.1 µF 2 µF

10 nF

0.1 µF

2 µF

Ferrite

Bead

Figure 10-7. Using ISOUSB211 with 1.8-V supplied with External Regulators

10.3.5 Example Configuration 3

In the application example shown in Figure 10-8, ISOUSB211 is powered using USB VBUS on the connector

side, and a local 3.3-V digital supply on the microcontroller side to generate V3P3Vx. The internal LDOs are used

to generate V1P8Vx on both sides like in Example Configuration 1. However, the VCC1 and VCC2 are connected to

VBUS and 3.3 VLV, not directly like in Example Configuration 1, but through resistors R1 (20 Ω, 250 mW) and

R2 (5 Ω, 50 mW) respectively.

The external resistors drop voltage, and dissipate power, helping reduce the power dissipation within

ISOUSB211, and the corresponding temperature rise. The resistor values are decided keeping in mind that

the VCCx voltage can be as low as 2.4 V. Additional 1-μF capacitors are needed on VCCx pins.

In this scenario, the total power consumption inside the IC from both sides taken together is:

VBUS1 × IVBUS1 + VBUS1 × IVCC1 - 20 Ω × IVCC1× IVCC1+ V3P3V2 × I3P3V2 + V3P3V2 × IVCC2- 5 Ω × IVCC2× IVCC2

Assuming 5.25 V as the maximum value of VBUS, and 3.5 V as the maximum value of the 3.3-V local supply,

the internal power dissipation is calculated as

5.25 V×13.5 mA + 5.25 V×96 mA - 20 Ω×96 mA×96 mA + 3.5 V×13.5 mA+3.5 V×96 mA - 5 Ω×96 mA×96 mA =

728 mW.

Since the junction-to-air thermal resistance is 44.2°C/W, this power dissipation results in a 33°C internal

temperature rise. Ambient temperature up to 117°C can be supported for this configuration.

ISOUSB211

SLLSFC5B – NOVEMBER 2021 – REVISED SEPTEMBER 2022

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