RT6056 datasheet(24/27 Pages) RICHTEK

24 / 27 page

RT6056

is a registered trademark of Richtek Technology Corporation

www.richtek.com

DS6056-00

April 2022

⚫

Gain Error, GE%

⚫

PSRR of offset voltage, PSRR

⚫

Common mode rejection, CMRR

⚫

The offset voltage caused by input bias current

⚫

Nonlinearity Error, NLIN%

Max Output Error Estimation

This section gives an example. The system bus voltage

for IN+ = 36V, supply voltage VS = 5V, shunt resistor is

accuracy 1% 2m

, the load current is 25A. To set the

design goals, the maximum output voltage errors are

calculated as follows:

Input offset voltage error

The rate of offset error in the total error can be estimated

directly from the specification table. The input offset

voltage is 10

V at TA = 25C, the error due to offset can

be obtained by the equation below :

OS(MAX)

OS_err

SENSE

μV

100% =

100% = 0.02%

25A





Sense Voltage Gain Error

From the electrical characteristics, the max gain error is

1%.

PSRR Error

The PSRR error is to estimate the error caused by

different

supply

voltage;

the

RT6056

device

specification gives the specified power supply voltage

for the input offset voltage specification as VS = 3.3V;

when the system supply voltage is not exactly 3.3V, it

may result in an additional error. RT6056 device gives

the maximum PSRR as 2.5

V/V. Calculate the PSRR

error by the equation below :

S_DS

S_SYS

SENSE

PSRR

PSRR_err =

100%

μV

3.3 5 2.5

100% = 0.0085%

25A

−



−





CMRR Error

The CMRR error means the input offset error is

influenced by the variation of common-mode voltage; in

real conditions, calculate the maximum input offset by

determining the actual common-mode voltage as

applied to RT6056. According to the RT6056 device

specification, it gives the common-mode rejection ratio

minimum as 126dB (0.501

V/V). The offset voltage in

the data sheet is specified with a common-mode voltage

that is 12V. To calculate the actual common-mode error

at system bus voltage :

(

)

126dB

μV

126dB =

= 0.501



CM_DS

CM_SYS

SENSE

CMRR

CMRR_err =

100%

μV

12 36 0.501

100% = 0.024%

25A

−



−





Input Bias Current Error

The input bias current flows into shunt resistor to cause

additional offset; this error is calculated with respect to

the ideal voltage across the sense voltage.

SHUNT

B_err

SENSE

μA 2m

100% =

100% = 0.0001%

25A









Nonlinearity Error

For ideal cases, the voltage gain is constant over full

sense ranges, but in the real application, the voltage

gain is not exactly constant, the nonlinearity gain may

cause some additional errors. In the specification, the

RT6056 gives the nonlinearity error as 0.1% over sense

voltage from 20mV to 80mV.

RT6056 Datasheet(PDF) 24 Page - Richtek Technology Corporation

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