K

R

V

I

CC

REF

CC

_

OUT

˜

12

TPS61235P, TPS61236P

SLVSCK4A – SEPTEMBER 2015 – REVISED MAY 2016

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Product Folder Links: TPS61235P TPS61236P

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Copyright © 2015–2016, Texas Instruments Incorporated

Feature Description (continued)

The CC pin can be connected to ground to disable the output current monitor function, and it will not affect the

CV operation.

8.3.4.3 Constant Current Operation

As Equation 1 shows, the CC pin voltage is proportional to the output current. The TPS6123x monitors the CC

(2)

Where:

K is the coefficient between the output current and the internal built current signal, K = 100,000.

If the load current is higher than the CC setting, the output voltage drops. A balance can be achieved if the load

TPS6123x can keep CC operation, output the constant current, and maintain the output voltage at the balanced

level. If the output voltage is pulled below the input voltage by a strong load before the balance is achieved, the

the device can complete the pre-charge phase, but its output voltage will be pulled down again in the switching

phase due to the limited output current, so an oscillation may happen.

In order to avoid the potential oscillation, the CC operation is only recommended for pure resistive loads or load

before the output voltage is pulled below the input voltage, so to avoid the TPS6123x entering into the startup

process.

should be set lower than the maximum output capability of the converter; otherwise, the TPS6123x will trigger the

over current protection first and fail to regulate the output current. Refer to the Over Current Protection section

for details.

The CC operation can be disabled by shorting the CC pin to ground. By doing so, the CC loop is disabled, so the

TPS6123x works as a normal boost converter to regulate the output voltage, and its maximum output current

capability is decided by the internal current limit.

8.3.5 Over Current Protection

To protect the device from over load condition, an internal cycle-by-cycle current limit is implemented. Once the

inductor valley current reaches the internal current limit, the protection is triggered and it clamps the valley

Figure 15 illustrates the valley current limit scheme. The average of the rectifier ripple current equals the output

begins.