VL53L5CX Ultra Lite Driver (ULD) - Enable/Disable Internal Charge Pump

[MFabb.1]

Hi,

The vl53l5cx_api.h file contains information about interesting functions to enable or disable the internal VCSEL charge pump:

/**
 * @brief This function is used to disable the VCSEL charge pump
 * This optimizes the power consumption of the device
 * To be used only if AVDD = 3.3V
 * @param (VL53L5CX_Configuration) *p_dev : VL53L5CX configuration structure.
 */
uint8_t vl53l5cx_enable_internal_cp(
		VL53L5CX_Configuration          *p_dev);
 
 
/**
 * @brief This function is used to disable the VCSEL charge pump
 * This optimizes the power consumption of the device
 * To be used only if AVDD = 3.3V
 * @param (VL53L5CX_Configuration) *p_dev : VL53L5CX configuration structure.
 */
uint8_t vl53l5cx_disable_internal_cp(
 	      VL53L5CX_Configuration          *p_dev);

Unfortunately, I cannot find other usefull information about this topic in the documentation.

What is the default state of the internal charge pump after initialization (ULD ver. 1.3.4)?

What is the expected power consumption delta when charge pump is enabled or disabled?

Could you explain how to correctly use the above functions to reduce the total power consumption of the VL53L5CX in each different power modes (LP Idle, HP idle, Ranging)?

In my setup AVDD = 3.3V requirement is already met.

Thank you

[John E KVAM · Accepted solution]

According to the data I have, the L5CX consumes, in continuous mode at 16 zones 60fps :

240 mW with AVDD = 3.3 V and charge pump enabled

180 mW with AVDD = 3.3 V and charge pump disabled

Now I also found:

The module uses an internal charge pump to generate a 3V6 voltage from AVDD which is the level required toenable the VCSEL.

However if a user has access to a 3V3 supply that can be guaranteed not to drop below 3V0, then the charge pump may be disabled via the configuration loaded before ranging starts.

Disabling the charge pump may be beneficial in some designs as it will reduce the typical current consumption on AVDD by upto 20mA.

Note: With the VCSEL power supply lowered from 3V6 to 3V0 there may be a small performance drop in ranging upto 6%.

Recommended limits on AVDD for use when the chage pump is enabled or disabled

Enabled - min is 2.5, typ is 2.8 and max is 3v3.

disabled - min is 3.0V, typ is 3.3V and max is 3.6V

[MFabb.1]

Hi John,

Thank you for your support.

I understood the working principle of the VCSEL charge pump.

I am only bit confused about your last sentence.

The min/typ/max voltage levels reported in the recommended operating conditions on the VL53L5CX datasheet are respectively 3.0/3.3/3.6V (in 3.3V configuration).

Hence, as suggested in your last sentence, the charge pump should be disabled by default in to meet the above conditions.

Could you double check if it is the case?

[John E KVAM]

In order to run our sensor in a cellphone, we were asked to make it work at 2.8V. In order to satisfy that requirement we added a charge pump to goose the voltage.

However if a user has access to a 3V3 supply that can be guaranteed not to drop below 3V0, then the charge pump may be disabled via the configuration loaded before ranging starts.

In the parts we sell to our non-cellphone customers we have the charge pump disabled, and really should have never included code that even mentions it.

USE the disabled option, and stick to the "disabled - min is 3.0V, typ is 3.3V and max is 3.6V"

[MFabb.1]

OK,

thank you John.