HA16113FPJ Datasheet, PDF (10/18 Pages) Hitachi Semiconductor – Dual Watchdog Timers

HA16113FPJ
External Circuit Constant Calculations (cont)
Item
V_NMI
V_STBY
WDT.
Equation
V _NMI
=
1.2 ×
1
+ ^{(R1 // 71.7)}
(R2 // 25)
NMI recovery voltage
(V_NMI high) is:
V_NMI high =
86.65 ₊ 86.65 _{+ 1.2}
R1 R2 // 25
1 + ^73.8
R1
(R1 and R2 are in kΩ)
V_STBY =
1.47×
1+
71
31.2 + (36.8 // R3)
(R3 is in kΩ)
Line1 =
0.31 × (Du – 24)
Cf × Rf
Line2 = Du (= 25%)*
Line3 = ^0.015
Cf × Rf
Line4 = ^{1 – Du}
2.1 × t_RH
Line5 = 99%*
Remarks
Voltage at which the NMI signal is output when Vout
drops. The NMI trigger voltage and NMI recovery voltage
can be trimmed by connecting resistors between the
NMIadj pin and Vout (R1), and between NMIadj and GND
(R2).
Vout
R1
NMIadj
R2
Vout
NMI
V_NMI
V_NMI high
NMI
t
Voltage at which the STBY signal is output when Vout
drops. The STBY trigger voltage can be adjusted by
connecting a resistor (R3) between the STBYadj pin and
GND. The STBY recovery voltage cannot be adjusted.
Vout
STBYadj
V_STBY high
Vout
STBY
V_STBY
R3
STBY
t
The watchdog timer function determines whether the P-
RUN pulse is normal or not. A reset pulse is output if P-
RUN is determined to be abnormal. The normal region is
the part bounded by Line1 to Line3 (or Line4) in the
diagram. Line4 applies in certain cases, depending on
C_R, Cf, and the state of P-RUN.
(Hz) _Line1
Du is the duty cycle of the P-RUN
pulse.
Du = ^tRH
t _RL + t _RH
Note: Line2 and Line5 are fixed.
Frequency
Normal area
Line2
Line3
Line4
Duty
Line5
(%)
10