
LV8130V
2. Control Methods
Control using the EI+ pin (TOC pin) Current feedback
The output transistor duty is determined according to the result of comparing the TOC pin voltage with the RF voltage.
When the RF voltage reaches the target voltage set by the control voltage, the PWM is turned off to maintain a
constant current.
The TOC pin is the CTL amplifier output pin, so the control voltage cannot be input directly to the TOC pin.
Normally, the CTL amplifier is used as a full-feedback amplifier (with the EI- pin connected to the TOC pin), and DC
voltage is input to the EI+ pin (EI+ pin voltage will become equal to the TOC pin voltage).
When the EI+ pin is in open state, the motor will be driven. So connect a pull-down resistor to the EI+ pin if the motor
should not operate when the EI+ pin is open. When performing control using the TOC pin voltage, leave the PWMIN
pin voltage open or connect the pin to ground.
Pulse control using the PWMIN pin
The output can be controlled based on the duty of the pulse signal input to the PWMIN pin.
However, as there is a delay time as shown in the figure below, the input duty and
the output duty do not match.
To PWMIN pin
Pulse input
The output is on when a low-level voltage is input to the PWM pin, and off when
a high-level voltage is input to the PWM pin. When the PWMIN pin is open, it
goes to high level and the output is off. When inverted logic input is required, this
can be supported by adding an external transistor (NPN).
When controlling motor operation from the PWMIN pin, connect the EI- pin to ground and the EI+ pin to the TOC
pin.
Note that the PWM oscillation is also used as the internal circuit clock, connect a capacitor (approx. 1000pF) to the
PWM pin, even if the PWMIN pin is used to control the motor.
Waveform Example (3)
PWMIN
OUT
PRE-H
PRE-L
Delay time 4
μs
10
μs
5.0V
1
10
μs
20.0V
2
10
μs
20.0V
3
10
μs
20.0V
4
Input DUTY -- Output DUTY
0
20
30
40
50
60
70
80
90
10
100
08
40
60
20
100
Input ONDUTY -- %
Output
ONDUTY
-
%
0
25kHz
30kHz
40kHz
50kHz
The LV8130 has a delay time of 4
μs (between when the PWMIN pin input changes from high (OFF) to low (ON) and
when the PRE-H output changes from low (OFF) to high (ON)) in order to realize synchronous rectification.
Therefore, the relationship between the input duty and the output duty is as shown in the right figure.
This input duty - output duty relationship changes according to the input frequency to maintain a constant delay time.
No.A1708-13/19