ISL98607

4. Application Information

FN8421 Rev.1.00

Page 21 of 29

Jun.3.19

4.14.3 Tie ENP and ENN together (1 GPIO control)

There is also an option to sequence the VN and VP regulators if there is only a single GPIO available in the

system. The method to control turn on/off by GPIO is valid when the respective enable bits in the ENABLE

register at Register Address 0x05 are set to ‘1’ (default). So, this method is used at IC power-ON (no I2C

communication is required).

If the ENP and ENN are tied together and both pulled HIGH, there is a default delay sequence in the IC. VP will

come up first and after 2ms VN soft-starts. For turn off, both VN and VP start to shut down together, but the decay

in the VP and VN voltage is controlled using the output capacitance value.

Figure 28 shows turn on when the ENN and ENP pins are tied together. There is a 2ms delay between VP and VN

turning on.

Figure 29 shows turn off when the ENN and ENP are tied together.

4.15 VP Output Hi-Z Mode

The ISL98607 VP regulator can be configured in a Hi-Z mode for when the regulators are turned off. Using I2C, bit

<b6> in the ENABLE register can be set to ‘1’ to disable the internal pull-down resistor (this is Hi-Z Mode).

Configuring the VP regulator in Hi-Z mode prevents any leakage current flowing between VP and VN when the

TFT-LCD is in sleep/standby mode, which minimizes the system power consumption.

Figure 26. On Sequence - 2 GPIO Control

Figure 27. Off Sequence - 2 GPIO Control

Figure 28. On Sequence - 1 GPIO Control

Figure 29. Off Sequence - 1 GPIO Control

ENN = 1V/Div (DC)

ENP = 1V/Div (DC)

1ms/Div

VP = 2V/Div (DC)

VN = 2V/Div (DC)

VP

VN

ENP

ENN

0V

-5V

0V

0V

+5V

ENN = 1V/Div (DC)

ENP = 1V/Div (DC)

VP = 2V/Div (DC)

VN = 2V/Div (DC)

1ms/Div

0V

0V

-5V

+5V

0V

ENN = 1V/Div (DC)

ENP = 1V/Div (DC)

VP = 2V/Div (DC)

VN = 2V/Div (DC)

1ms/Div

VP

VN

ENP

ENN

0V

-5V

0V

+5V

0V

ENN = 1V/Div (DC)

ENP = 1V/Div (DC)

VP = 2V/Div (DC)

VN = 2V/Div (DC)

1ms/Div

VP

VN

ENP

ENN

0V

-5V

0V

0V

+5V