BD64550EFV_1 Datasheet, PDF (12/17 Pages) Rohm – System Driver for Ink Jet Printers

BD64550EFV
Technical Note
④Low voltage protection/overvoltage protection circuit
All functions are shutout on the condition of setting value (+30%, -30%) while DSEN pin voltage (pin 18) of switching
regulator circuit is monitored.
Set voltage
Mask time
State after operation
VSWLV
0.60(V)
10µsec
All function shutout
VSWOH
1.20(V)
10µsec
All function shutout
Note that output overvoltage and output low voltage protection does not work until soft start count finish (32.8 ms, Typ.)
at the time of start up of DC/DC power after power-on.
Operating
Switching regulator
OFF
Series regulator
OFF
DC motor
OFF
RESET
L
Re-start
Again power-on
DSEN
0.9V
BIAS
DAC
SS
COUNTER
DRIVER
0.60V
1.21V
Mask during
soft starting
All function
off circuit
SWOUT
DSEN
Fig.27 Switching Regulator Block Diagram
○RESET function
Power-on RESET circuit is built-in for VM power source.
H is output at RESET pin through DELAY time of internal counter when power voltage goes up to V_MPORH (6.5 V, Typ.) or
higher at the time of power-on. In addition, hysteresis is set up at the time of power-down to output L at RESET pin with
VMPORL (6.1 V, Typ.) And no response time (2.5µs, Typ.) of voltage detection is set in order to avoid wrong detection by
sudden power-off.If protection circuits other than overcurrent protection of motor starts operating, RESET is not released if
VM power is not on again.
VM
Internal
regulator
B.G
OSC
RESET1 _DCOC
DCOC
Counter
VM
RESET2
VM
UVLO _RESET1
POWER
monitor
AND
POR _AND
Counter
RESET
BG
Protection detection other than
DCOC
BG
Latch circuit
SWOFF
OSC
SS
Counter
（SOFT START）
Fig.28 RESET Internal Circuit Block Diagram
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12/16
2010.06 - Rev.A