RT6056GF datasheet(23/27 Pages) RICHTEK

23 / 27 page

RT6056

is a registered trademark of Richtek Technology Corporation

DS6056-00

April 2022

www.richtek.com

Application Information

Power Up

The VS pin must exceed the Power-On Reset threshold

(VPOR) of 2V to keep the RT6056 out of power-on reset.

Power-on reset will clear all of the register data.

Choosing the Sense Resistor

A high RSHUNT value causes the power-source voltage

to drop due to IR loss. For minimal voltage loss, use the

lowest RSHUNT value. VSENSE full scale should be less

than the full code of

−81.9175mV to 81.92mV. For

best performance with a 3.3V supply voltage, select

RSHUNT to provide approximately 40mV~60mV of

sense voltage for the full-scale current in each

application.

At low current levels, a high RSHUNT value allows lower

currents more accurately because offsets are less

significant when the sense voltage is larger.

At high current levels, the I2R loss in RSHUNT can be

significant. Notice the resistor value and power

dissipation rating when choosing. Also, the sense

resistor’s value might drift if it is allowed to heat up

excessively. The precision VOS 10

V (max) and Gain

Error 0.1% (max) of the RT6056 allows the use of small

sense resistors to reduce power dissipation and reduce

hot spots.

Filtering and Input Considerations

The RT6056 provides several methods to reduce the

effect from the input noise; for example, conversion time

and averaging mode can be flexibly chosen through the

damaging from the load dumps, reverse battery

protection, fast load-switching and inductive kickback

voltages, the input filter and input voltage clamping

schemes are needed to protect the device during such

conditions.

Figure 7 shows the recommended schematic for input

filtering. Filtering at the input means current noise is not

amplified and the RT6056 can drive a cleaner signal into

the ADC without an output filter loading down the ADC.

VBUS

IN+

IN-

Noisy Load

RSHUNT

RFILTER1

CFILTER

RFILTER2

Figure 7. Input Filter

If the chosen device states that the Absolute Maximum

Common-Mode Voltage rating cannot exceed system

maximum expected voltage surge, then it needs input

protection. Along with some passives, the current

sensor needs transient voltage suppression (TVS) or

Zener diodes at the inputs for protection. Figure 8

shows an example using the cost-optimized current

sensor.

VBUS

IN+

IN-

Noisy Load

RSHUNT

RFILTER1

CFILTER

RFILTER2

Figure 8. RT6056 with Input Protection

Total Error Analysis

In order to optimize the design, the first is to analyze the

contribution of each error; the main influences of sense

voltage errors can be identified as follows :

⚫

The tolerance of shunt resistor (RSHUNT)

⚫

Sense offset voltage, VS_OS. When the sense voltage

is small, especially low load current and small shunt

resistance, the error is dominated by the input offset

error.

RT6056GF Datasheet(PDF) 23 Page - Richtek Technology Corporation

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