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L6615

2

CURRENT SENSE SECTION

A sense resistor is typically used to generate the voltage drop, proportional to the load current, measured

through two identical resistors (RG1 and RG2).

The CSA consists of 2 sections (see fig. 10), one responsible for the high side sensing, the other for low

side sensing. An internal comparator activates the relevant section in accordance with the voltage present

at CS+ pin: if this voltage is higher than 1.6V (typ), then the high side sensing section will be activated

the controlled current mirror to:

– sink current from the CS+ pin in case of high side sensing (neglecting input bias current, no current flows

through CS- pin);

– source current from the CS- pin in case of low side sensing (neglecting input bias current, no current

flows through CS- pin).

The local feedback imposes the same voltage at the current sense input pins, so under closed loop con-

The current

at the current sense pins.

In noisy applications, two capacitors of small value (e.g. 1nF) connected between current sense pins and

ground could be useful to clean the signal at the input of the current sense amplifier.

For low voltage buses application, see paragraph 7.

Figure 10. Current sense section

I

CS

I

OU T

R

SEN SE

⋅

R

G

---------------------------------------

=

V

SH

V

SNS

R

G

-------------- R

CGA

⋅

=

COMPARE

CS-

CS+

LSA

CGA

PS+

LOAD(+)

I

OUT

R

SENSE

R

G

R

G

V

SENSE

I

CGA

I

CS+

V

RG

HSA

+

-

+

-

R

CGA

L6615

1.6V

CONTROLLED

CURRENT

MIRROR

1:1

SINK

CSA

LOAD(-) / GND

PS-

COMPARE

CS-

CS+

LSA

CGA

I

OUT

R

SENSE

R

G

R

G

V

SENSE

I

CGA

V

RG

HSA

+

-

+

-

R

CGA

L6615

1.6V

CONTROLLED

CURRENT

MIRROR

SOURCE

CSA

1:1

I

CS-

COMPARE

CS-

CS+

LSA

CGA

PS+

LOAD(+)

I

OUT

R

SENSE

R

G

R

G

V

SENSE

I

CGA

I

CS+

V

RG

HSA

+

-

+

-

R

CGA

L6615

1.6V

CONTROLLED

CURRENT

MIRROR

1:1

SINK

CSA

LOAD(-) / GND

PS-

COMPARE

CS-

CS+

LSA

CGA

I

OUT

R

SENSE

R

G

R

G

V

SENSE

I

CGA

V

RG

HSA

+

-

+

-

R

CGA

L6615

1.6V

CONTROLLED

CURRENT

MIRROR

SOURCE

CSA

1:1

I

CS-

a) high side sensing

b) low side sensing