Backlight

NHL-2NA grip keyboard uses six white backlight LEDs. These LEDs are "smart LEDs" (0.6mm height). The LED type is LWL88S, NMP code 4860331. NHL-2NA grip uses brightness groups M1-M2, N1-N2 and P1. There is only one brightness group in one grip-module.

Electrical interface

The idea is to connect these six LEDs parallel. LEDs are using current that is taken from battery voltage. The voltage is controlled by charge pump (NMP code 4341137) and the current by serial resistor. The idea of the charge pump is to keep the supply voltage of the LEDs constant although Vbat changes. Serial resistors limit the current that goes to LEDs. Current for one LED is ~4mA. The circuit and LEDs consume ~52mA current.

LEDs need one line of flex (Called 1). Called 1 controls the charge pump SD pin. Called 1 signal rises close to Vbat voltage (required for the SD signal in specification of the current pump). The output of the current pump is 4.1V (@Vbat 3.0V to 4.2V).

Figure 38: Electrical implementation of the grip keyboard backlight

Figure 38: Electrical implementation of the grip keyboard backlight

BatGND
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