MB39C831 Datasheet, PDF (9/40 Pages) Cypress Semiconductor – Ultra Low Voltage Boost Power Management IC for Solar/Thermal Energy Harvesting Datasheet

MB39C831
7. Function
7.1 Outline of Operation
MB39C831 is the boost DC/DC converter which has the function controls for the synchronous rectification operation of the
integrated FET using the frequency set by the built-in oscillator. The converter operates in PFM at light load currents.
This converter is equipped with a constant voltage mode (MPPT_ENA = L) and a charge mode (MPPT_ENA = H).
Constant voltage mode: An output terminal VOUT outputs a constant voltage set by the S2, S1 and S0 pins.
Charge mode
: The input voltage (VIN) is adjusted by following the MPPT value set by the S2, S1 and S0 pins, and a
Li-ion battery can be charged.
7.2 Start-up/Shut-down Sequence
Constant Voltage Mode: MPPT_ENA = L, ENA = H
In order to operate the constant voltage mode, it supposes that to connect ceramic capacitor, electrolytic capacitor, tantalum
capacitor, electric double layered capacitor, and so on, to VCC pin. See Figure 11-1 circuit to use the constant voltage mode.
The constant voltage mode is necessary to set MPPT_ENA = L and ENA = H. MPPT_ENA pin is connected to GND, and ENA
pin is connected to VCC pin. See Figure 10-1 Start-up/shut-down sequences of constant voltage mode.
Figure 7-1 Start-up/Shut-down Sequences of Constant Voltage Mode (MPPT_ENA=L, ENA=H)
0.35V
VDD Voltage _0V
VST
startup voltage _0V
0.2V
0V
VCC Voltage
0V
VOUT Voltage
0V
LX
switching
VCC-VOUT
SW1
OFF
DET1
0V
2.9V
VCC=VOUT
2.6V
2.6V
0V
2.9V
Constant Voltage Operation
2.6V
0V
ON
OFF
Same as VCC Voltage
0V
DET0
0V
0V
U
[1]
S
DS
[2] [3]
DD
[4]
D
U
U
[5]
[6]
Mark
U
S
D
State
UVLO
Start-Up
Boost DC/DC
[1] When 0.35V (Minimum input voltage at start-up: VSTART) or higher voltage is applied to the VDD pin, the start-up circuit
activates charging the VCC capacitor C2 (see Figure 3-1).
Document Number: 002-08404 Rev *A
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