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DA6102

6-Channel High Efficiency PMIC for 2-Cell Systems

Datasheet

Revision 2.1

28-Apr-2017

37 of 82

9.6

Channel 1, BuckBoost Regulator

Channel 1 is a 4-switch BuckBoost. This channel consists of two buck switches connected between

VIN1, LXD1, and GND; and two boost switches connected between VO1, LXU1, and GND. For most

of the input voltage range, where the battery voltage is greater than VO1, channel 1 will operate in

buck mode. In buck mode, the high side boost switch is turned on at 100% duty, which is the most

efficient mode of operation.

As the input voltage approaches VO1 and the high side buck duty increases to 80%, the boost stage

turns on. When in BuckBoost mode, the buck switch operates at a nearly constant duty cycle, while

the boost duty varies with input voltage. The BuckBoost turn-on threshold can be estimated as

shown:

Vout

Vin

BOOST 

And once in BuckBoost mode (assuming 80% buck duty) the boost duty can be calculated as:

Vout

Vin

BOOST







Once the boost begins switching, Channel 1 can maintain regulation with input voltages as low as

2.9 V. In BuckBoost mode, all four switches are switching with the boost stage operating at

increasing duty cycle as input voltage decreases. Channel 1 does not have a boost-only mode.

The buck to BuckBoost transition point can be adjusted if necessary via the BB_OPT register (0x31).

A lower duty threshold will degrade efficiency as there will be more time spent in the 4-switch

BuckBoost region. However, a lower threshold may improve the performance when transitioning

between modes. The default setting of 80 % is recommended for nearly all applications. In some

cases such as high switching frequency, the buck may hit maximum duty cycle before the BuckBoost

transition occurs. As the input voltage drops lower than this point, Channel1 will drop out of

regulation before the boost stage begins switching. To prevent this, either reduce the transition

threshold, or enable the pulse skipping function which essentially increases the maximum duty cycle

capability.

Channel 1 maximum load current is rated to 700 mA, which includes the current required to support

the LDO1 output, LDSW1, and VDR rail. The maximum expected load from the VO1 pin is expected

to be less than 500 mA. Because Channel 1 supports additional internal loads, the current limit

threshold is set accordingly.

Although Channel 1 is capable of regulating from very low input voltage, load current capability may

be limited as input voltage drops. The maximum peak inductor current occurs in BuckBoost mode

and can be approximated as shown below.

fsw

Vin

Iout

BOOST

PEAK









Highest peak and average inductor current occurs at the minimum input voltage.

Channel 1 can also be configured to operate as a buck-only regulator. This function is enabled in the

BB_OPT register (0x31). To configure Channel 1 as a buck-only switching regulator, disconnect L1

from the LXU1 pin and connect it directly to the output cap and FB pin. The VO1 and LXU1 pins

should be connected to ground to minimize leakage current. In buck only mode, the pulse skipping

function remains available and operates the same as the other switching channels.

9.7

Channels 2 and 4, Buck Regulators

Channels 2 and 4 are integrated synchronous buck switching regulators with nearly identical control

and features. Channel 2 has a maximum load current capability of 2.2 A with an output voltage range

of 3.0 V to 4.55 V. Due to the low on-time required at high input voltage, Channel 2 should be

operated at a maximum switching frequency of 2 MHz. If the on-time reaches minimum, Channel 2

will be unregulated at higher input voltage.

DA6102 Datasheet(PDF) 37 Page - Dialog Semiconductor

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