DA9062_16 Datasheet, PDF (40/96 Pages) Dialog Semiconductor – PMIC for applications requiring up to 8.5 A

DA9062
PMIC for applications requiring up to 8.5 A
7.7 Switching Regulators
DA9062 includes four step-down switching regulators operating at 3 MHz. All switching regulators
employ a synchronous topology with an internal NFET, thus eliminating the need for an external
Schottky diode. The output voltage can be set in 10 mV steps (20 mV steps for Buck3) and the
regulation accuracy is ±3 % over the whole operating temperature range. Static line and load
regulation are also considered in this accuracy.
The switching frequency (3 MHz) is high enough to warrant the use of a small 1.0 µH inductor. The
programming of the converter current limit depends on the coil parameters, as illustrated in Table 24.
Table 24: Buck Current Limit
Min. ISAT (mA)
1750
1460
1180
940
Frequency (MHz)
3
3
3
3
Buck current limit (mA)
1500
1200
950
750
7.7.1 Control
The buck can be enabled manually by writing directly to a control register, with an external signal
connected to GPI, see Section 7.3.1.1, or by assigning it to a power sequencer step, see
Section 7.9.2. Each buck converter features two voltage control registers
(VBUCK<x>_A/VBUCK<x>_B) which can be programmed with two different voltages. The active
setting can then be selected via a control bit (VBUCK<x>_SEL), via a GPI, see Section 7.3.1.1, or
automatically based on the power mode of DA9062.
7.7.2 Output Voltage Slewing
To limit in-rush current from the input supply, the buck converters can achieve a new output voltage
with controlled ramping. Ramping is achieved by stepping through all the V_BUCK values between the
old and new settings, at a rate defined by SLEW_RATE. The actual output slew rate, in mV/µs, for a
particular buck converter is then defined by the minimum voltage step of that buck and the common
step time programmed in SLEW_RATE. During PFM mode, the negative slew rate is load dependent
and might be lower than the one mentioned above. An event E_DVC_RDY is triggered when all buck
converters have reached their target voltage.
7.7.3 Soft-Start
The buck converter supports two options for starting up. The normal start-up option ramps up the
power rail as fast as possible, typically within 1 ms. This implies a high in-rush current. The slow
start-up is selected by setting BUCK_SLOWSTART, which increases the start-up time and limits the
input current.
7.7.4 Active Discharge
When switching off a buck converter the output rail can be actively discharged. This feature is
enabled by setting BUCK_ACTV_DISCHRG. The discharge is implemented by ramping down the
output voltage using DVC.
7.7.5 Peak Current Limit
All buck converters feature a programmable current limit (BUCK<x>_ILIM). The current limit protects
the inductor and the pass devices from excessive current. If the current limit is exceeded, the buck
continues to run normally but the duty cycle is limited.
Datasheet
Revision 3.3
40 of 96
24-Nov-2016
© 2016 Dialog Semiconductor