MCP19110_16 Datasheet, PDF (18/226 Pages) Microchip Technology – Digitally-Enhanced Power Analog Controller

MCP19110/11
3.3 Output Voltage
The output voltage is configured by the settings
contained in the OVCCON and OVFCON registers. No
external resistor divider is needed to set the output
voltage. Refer to Section 6.10 “Output Voltage
Configuration”.
The MCP19110/11 contains a unity gain differential
amplifier used for remote sensing of the output voltage.
Connect the +V_SEN and -V_SEN pins directly at the load
for better load regulation. The +V_SEN and -V_SEN are the
positive and negative inputs, respectively, of the
differential amplifier.
3.4 Switching Frequency
The switching frequency is configurable over the range
of 100 kHz to 1.6 MHz. The Timer2 module is used to
generate the HDRV/LDRV switching frequency. Refer
to Section 26.0 “PWM Module” for more information.
Example 3-1 shows how to configure the
MCP19110/11 for a switching frequency of 300 kHz.
EXAMPLE 3-1: CONFIGURING F_SW
BANKSEL
CLRF
CLRF
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
T2CON
T2CON
TMR2
0x19
PR2
0x0A
PWMRL
0x00
PWMPHL
0x04
T2CON
;Turn off Timer2
;Initialize module
;Fsw=300 kHz
;Max duty cycle=40%
;No phase shift
;Turn on Timer2
3.5 Compensation
The MCP19110/11 is an analog peak current mode
controller with integrated adjustable compensation.
The CMPZCON register is used to adjust the
compensation zero frequency and gain. Figure 3-1
shows the internal compensation network with the
output differential amplifier.
FIGURE 3-1:
SIMPLIFIED INTERNAL
COMPENSATION
+V_SEN
-V_SEN
V_REF
3.6 Slope Compensation
In current mode control systems, slope compensation
needs to be added to the control path to help prevent
subharmonic oscillation when operating with greater
than 50% duty cycle. In the MCP19110/11, a negative
slope is added to the error amplifier output signal
before it is compared to the current sense signal. The
amount of slope added is controlled by the
SLPCRCON register, Register 6-7.
Note 1: To enable the slope compensation
circuitry, the ABECON<SLCPBY> bit
must be cleared.
The amount of slope compensation added should be
equal to the inductor current down slope during the
high-side off time.
3.7 Current Sense
The output current is differentially sensed by the
MCP19110/11. The sense element can be either a
resistor placed in series with the output, or the series
resistance of the inductor. If the inductor series resis-
tance is used, a filter is needed to remove the large AC
component of the voltage that appears across the
inductor and leave only the small AC voltage that
appears across the inductor resistance, as shown in
Figure 3-2. This small AC voltage is representative of
the output current.
FIGURE 3-2:
INDUCTOR CURRENT
SENSE FILTER
VIN
-ISEN
+ISEN
HDRV
PHASE
LDRV
RS
CS
L
RL
To Load
The value of R_S and C_S can be found by using
Equation 3-3. When the current sense filter time
constant is set equal to the inductor time constant, the
voltage appearing across C_S approximates the current
flowing in the inductor, multiplied by the inductor
resistance.
DS20002331D-page 18
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