CS1610A/11A

CS1612A/13A

DS976PP4

13

5.7.4

Overcurrent Protection

Overcurrent protection (OCP) is implemented by monitoring

the voltage across the second stage sense resistor. If this

condition occurs. The IC output is disabled, and the controller

attempts to restart after one second.

5.7.5

Open Loop Protection

Both open loop protection (OLP) and protection against a

short of the second stage sense resistor are implemented by

monitoring the voltage across the sense resistor. If the voltage

on pin FBSENSE does not reach protection OLP threshold

attempts to restart after one second.

5.8

Overtemperature Protection

The CS1610A/11A/12A/13A incorporates both internal over-

temperature protection (iOTP) and the ability to connect an ex-

ternal overtemperature sense circuit for IC protection.

Typically, a negative temperature coefficient (NTC) thermistor

is used.

5.8.1

Internal Overtemperature Protection

Internal overtemperature protection (iOTP) is activated, and

switching is disabled, when the die temperature of the device

exceeds 135°C. There is a hysteresis of about 14°C before

resuming normal operation.

5.8.2

External Overtemperature Protection

The external overtemperature protection (eOTP) pin is used to

implement overtemperature protection using an external NTC

thermistor. The total resistance on the eOTP pin is converted

to an 8-bit digital ‘CODE’ (which gives an indication of the

temperature) using a digital feedback loop, which adjusts

1.25V. Figure 17 illustrates the functional block diagram when

connecting an optional external NTC temperature sensor to

the eOTP circuit.

source with a full-scale current of 80

A. See Equation 9:

When the loop is in equilibrium, the voltage on pin eOTP

‘CODE’ output by the ADC is used to generate

In

normal

operating

mode,

line-cycle by a single ± LSB step. See Equation 10:

Using Equation 10 solve for digital CODE. See Equation 11:

The tracking range of this resistance ADC is approximately

15.5k

resistance of the NTC thermistor to fall within this ADC

tracking range so that the entire 8-bit dynamic range of the

ADC is well used. A 14k

 (±1% tolerance) series resistor is

required to allow measurements of up to 130°C to be within

the eOTP tracking range when a 100k

 NTC thermistor with

a Beta of 4334 is used. The eOTP tracking circuit is designed

to function accurately with external capacitance up to 470pF.

A higher 8-bit code output reflects a lower resistance and

hence a higher external temperature.

The ADC output code is filtered to suppress noise and

compared against a reference code that corresponds to

125/130°C. If the temperature exceeds this threshold, the

chip enters an external overtemperature state and shuts

down. This is not a latched protection state, and the ADC

keeps tracking the temperature in this state in order to clear

the fault state once the temperature drops below 110°C.

CS1610A/11A/12A/13A

+

-

I

CONNE CT

V

CONNE CT

(th)

Comp_Out

eOTP

Control

eOTP

NTC

V

DD

10

(Optional )

Figure 17. eOTP Functional Diagram



R

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

=

[Eq.9]

CODE

2

N

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





+

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

=

[Eq.10]

CODE

2

N





+





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

=

256 1.25 V



80

A



+





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

=

4M



+



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

=

[Eq.11]