Datasheet

6 Detailed description
The SPV1040 is a monolithic, high efficiency, low voltage, self-powered DC-DC converter that operates over a 0.3
V to 5.5 V DC input voltage range and provides a single output voltage. The device provides regulated output
voltage and current by sensing the VCTRL feedback of the external resistor divider and the voltage drop on the
external sense resistor Rs, respectively. High efficiency is ensured by low power consumption in any working
mode and by the embedded perturb and observe MPPT algorithm. The SPV1040 guarantees its own safety and
application safety by stopping the N-channel power switch in case of overcurrent or overtemperature conditions.
6.1 Soft-start
In order to guarantee the power-up even when VOUT is very low (battery completely discharged), a proper start-
up strategy has been implemented. Taking into account that the device is powered by the VOUT voltage, If VOUT
is lower than 0.8 V, the device moves from power off to soft-start mode and the current flows from the input to
output through the intrinsic body diode of the synchronous rectifier. In this condition VOUT follows the LX voltage.
The IC exits start-up mode when VOUT reaches 0.8 V.
6.2 Start-up mode
When VOUT goes above 0.8 V but it is still lower than 2 V, a proper biasing of both MOSFETs is not guaranteed
yet. In such conditions, the N-channel power switch is forced ON with a fixed duty cycle and the energy is
transferred to the load via the intrinsic body diode of the P-channel synchronous switch. If the shutdown
overcurrent limit is exceeded, the power switch is immediately turned OFF. The SPV1040 leaves start-up mode as
soon as VOUT goes above 2 V.
6.3 MPPT mode
Once the device has exited start-up mode, the SPV1040 enters MPPT mode to search for the maximum power
point. The perturb and observe algorithm is based on monitoring either the voltage or the current supplied by the
DC power source unit so that the PWM signal duty cycle is increased or decreased step-by-step according to the
input power trend. Refer to Figure 6 , which illustrates the MPPT working principle.
6.4 Constant voltage regulation
The constant voltage control loop consists of an internal voltage reference, an op-amp and an external resistor
divider that senses the battery voltage and fixes the voltage regulation set-point at the value specified by the user.
6.5 Constant current regulation
The constant current control loop consists of an op-amp and an external sense resistor that feeds the current
sensing circuit with a voltage proportional to the DC output current. This resistor determines the current regulation
set-point and must be adequately rated in terms of power dissipation. It provides the capability to fix the maximum
output current to protect the battery.
6.6 Overcurrent protection (OVC)
When the current that flows through the inductor reaches 1.8 A (overcurrent shutdown limit), the N-channel power
switch is immediately forced OFF and the P-channel synchronous rectifier is switched ON. Once the overcurrent
condition has expired (the inductor current goes below 1.8 A
pk
) the N-channel power switch is turned back ON.
6.7 Overtemperature protection
When the temperature sensed at silicon level reaches 155 °C (overtemperature shutdown limit), the N-channel
power switch is immediately forced OFF and the P-channel synchronous rectifier is switched ON. The device
becomes operative again as soon as the silicon temperature goes below 130 °C.
6.8 Shutdown mode
The XSHUT pin low shuts OFF all internal circuitry, achieving the lowest power consumption mode.
SPV1040
Detailed description
DS6991 - Rev 8
page 8/17