SM72445 Datasheet, PDF (13/19 Pages) Texas Instruments – Programmable Maximum Power Point Tracking Controller With Adjustable PWM Frequency

reg4 Register Description
Bits
Field
Reset Value
R/W
55:32
RSVD
24'd0
R/W
31:24
Vout offset
8'h0
R/W
23:16
Iout offset
8'h0
R/W
15:8
Vin offset
8'h0
R/W
7:0
Iin offset
8'h0
R/W
Bit Field Description
Reserved
Voltage out offset
Current out offset
Voltage in offset
Current in offset
reg5 Register Description
Bits
Field
Reset Value
R/W
55:40
RSVD
15'd0
R/W
39:30
iin_hi_th
10'd40
R/W
29:20
iin_lo_th
10'd24
R/W
19:10
iout_hi_th
10'd40
R/W
9:0
iout_lo_th
10'd24
R/W
Bit Field Description
Reserved
Current in high threshold for start
Current in low threshold for start
Current out high threshold for start
Current out low threshold for start
The open loop operation allows the user to set a fixed oper-
ating duty cycle (buck or boost) on the converter. The unit will
not sense current or voltage in this mode and will perform an
internal reset when exiting open loop mode.
The bb_reset bit performs a limited reset of the IC. While this
bit is set high, the unit will not output any driving signal and
will not sense any input. When this bit is transited back to zero,
the unit will go through its initialization phase according to the
programming mode set and possible I2C overrides. The IC
will NOT perform a sample of the A0–A6 input when the
bb_reset bit is cleared.
To change the PWM frequency options the first time after
power up, the following programming sequence must be
used :
• set bb_reset bit (reg3[2]), set over-ride bit (reg3[46]), set
to the desired PWM code (reg3[42:40])
• reset bb_reset bit, keep over-ride bit, keep the desired
PWM code
To change PWM options subsequent to an earlier program-
ming :
• set bb_reset bit, reset over-ride bit, set to the desired PWM
code
• reset bb_reset bit, reset over-ride bit, keep the desired
PWM code
• set bb_reset bit, set over-ride bit, keep the desired PWM
code
• reset bb_reset bit, keep over-ride bit, keep the desired
PWM code
The switching frequency will be returned to the default exter-
nal resistor setting after each hard reset of the IC.
The “tdoff” and” tdon” (REG3[14:19]) parameters allow mod-
ification of the dead time. the dead time for the turning on of
the synchronous rectifier (affecting buck and boost mode) will
be set by (td_on/256)*(1/f_switch). The default parameter for
td_on is 3.
The dead time for the turning on of the main switch after the
synchronous rectifier as turned off (affecting buck and boost
mode) will be set by (td_off/256)*(1/f_switch). The default pa-
rameter for td_off is 3. The dead time parameters are returned
to their default value after each hard reset of the IC.
The offsets are 8 bit signed numbers which are added or sub-
stracted to the results of the A/D converter and affect the
sensed values displayed in Register 0 as well as the thresh-
olds.
Using the I2C port, the user will be able to control the duty
cycle of the PWM signal. Input and output voltage and current
offsets can also be controlled using I2C on register 4. Control
registers are available for additional flexibility.
The thresholds iin_hi_th, iin_lo_th, iout_hi_th, iout_lo_th, in
reg5 are compared to the values read in by the ADC on the
AIIN and AIOUT pins. Scaling is set by the scaling of the ana-
log signal fed into AIIN and AIOUT. These 10–bit values
determine the entry and exit conditions for MPPT. The startup
high thresholds set the voltages at pin AIIN and AIOUT above
which the unit will begin transition from PM_Startup state to
MPPT state. The low thresholds set the voltage below which
the unit will transition back to PM_Startup (stand-by). The ini-
tial thresholds are a function of the value programmed in A6.
As determined by , if A6 was between 0 and 1.56V at start-
up, the thresholds will be 0.023*VDDA and 0.039*VDDA.
To run the system in Open Loop configuration, the Soft Reset
bit must be set then cleared. The ADC channels are inactive
when the device is used in Open Loop configuration.
COMMUNICATING WITH THE SM72445
The SCL line is an input, the SDA line is bidirectional, and the
device address can be set by the I2C0, I2C1 and I2C2 pins.
Three device address pins allow connection of up to 7
SM72445s to the same I2C master. A pull-up resistor
(10kΩ) to a 5V supply is used to set a bit 1 on the device
address. Device addressing for slaves are as follows:
I2C0
I2C1
I2C2
Hex
0
0
1
0x1
0
1
0
0x2
0
1
1
0x3
1
0
0
0x4
1
0
1
0x5
1
1
0
0x6
1
1
1
0x7
13
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