M62211FP Ver la hoja de datos (PDF) - Renesas Electronics
Número de pieza
componentes Descripción
Lista de partido
M62211FP Datasheet PDF : 12 Pages
| |||
M62211P/FP
3. Soft Start, DTC, and Short Protection
1) Soft Start (The peripheral circuit is shown in Figure 1)
When the power is turned ON, IN1 and IN2 are at 0 V level. Therefore, the FB terminal is fixed to High level. The
DTC terminal goes up gradually starting from 0 V due to the internal charge current and the external CDTC.
When the level of DTC terminal reaches the lower limit of the triangular wave of the oscillator, PWM comparator
and the output circuit go into operation causing the output voltage, "VO" of the DC/DC converter to rise. The charge
current is designed to be approximately 35 µA.
FB
OSC
DTC
1.0 V
0.45 V
OFF
External Tr collector
ON
Figure 2
2) DTC
The dead time control is set by installing a resistor between the DTC terminal and GND. However, the DTC
terminal serves as the short protection circuit also. Therefore, its set up depends on whether the short protection
circuit is used and not.
When the short protection circuit is used
At this time, the charge current for DTC is approximately 10 µA. Therefore, RDTC should be set to 40 kΩ to 110
kΩ.
When the short protection circuit is not used
At this time, the charge current for DTC is approximately 45 µA. Therefore, RDTC is set to 12 kΩ to 25 kΩ.
3) Short protection circuit
The short protection circuit used the timer latch system. It is determined by setting the capacity used for the soft
start connected to the DTC terminal.
Figure 3 shows the short protection circuit and the timing chart for various modes.
When the power is turned on, the FB terminal goes high (approx. 2.4 V) and the DTC terminal goes low. (goes up
slowly from 0 V) Thus, approximately 35 µA current will flow when SW1: ON and SW2: OFF. The potential,
namely the potential of the FB terminal is in the amplitude of the triangular wave, SW1 will be OFF and SW2 will
be ON and approximately 45 µA will flow into the DTC terminal. This discharge current will cause the DTC
terminal to drop from 1.15 V.
At this time, if the potential of the FB terminal goes to the control potential before the potential at the DTC terminal
goes lower than 0.45 V which is the lower limit value of the triangular wave and if the potential of the FB terminal
is lower than the potential of the DTC terminal, then the system is activated.
When the output is shorted, the system is either activated or latched depending on whether the time for the high
potential of the FB terminal reaches the potential of the control state is long or short. (For detail, see [II] and [IV] of
the Mode)
There are two ways to go back to operation after the latch to shut off output. Either method can restart with soft
start.
1. Turning on the VCC.
2. Make the FB terminal to go to the low potential of 1.25 V or less. Then, it is cancelled.
REJ03D0842-0201 Rev.2.01 Nov 14, 2007
Page 8 of 11
Share Link: 