RESET
Circuit Waveform
(1) = No Delay Capacitor
(2) = With Delay Capacitor
V
OUT
V
RH
V
V
RT(ON)
RESET
(3) = Max:
Voltage (1.0V)
RT(OFF)
(1)
RESET
(2)
(3)
V
RL
t
Delay
Delay
V
DH
V
DC(HI)
V
DC(LO)
V
DIS
(2)
RESET Circuit Functional Description
put voltage is above VRT(ON). Otherwise, the Delay lead
sinks current to ground (used to discharge the delay
capacitor). The discharge current is latched ON when the
output voltage is below VRT(OFF). The Delay capacitor is
fully discharged anytime the output voltage falls out of
regulation, even for a short period of time. This feature
The CS8129
function has hysteresis on both the
RESET
reset and delay comparators, a latching Delay capacitor
discharge circuit, and operates down to 1V.
The
circuit output is an open collector type with
RESET
ON and OFF parameters as specified. The RESET output
NPN transistor is controlled by the two circuits described
(see Block Diagram).
ensures a controlled
pulse is generated following
RESET
detection of an error condition. The circuit allows
the output transistor to go to the OFF (open) state
RESET
only when the voltage on the Delay lead is higher than
VDC(HI)
Low Voltage Inhibit Circuit
.
This circuit monitors output voltage, and when output
voltage is below the specified minimum causes the
The Delay time for the
the formula:
function is calculated from
RESET
output transistor to be in the ON (saturation)
RESET
C
Delay x VDelay Threshold
ICharge
state. When the output voltage is above the specified level,
this circuit permits the RESET output transistor to go into
Delay time =
the OFF state if allowed by the
Delay circuit.
RESET
Delay time = CDelay(µF) x 3.2 x 105
Reset Delay Circuit
If CDelay=0.1µF, Delay time (ms)=32ms ± 50%: i.e. 16ms to
48ms. The tolerance of the capacitor must be taken into
account to calculate the total variation in the delay time.
This circuit provides a programmable (by external capaci-
tor) delay on the output lead. The Delay lead pro-
vides source current to the external delay capacitor only
when the "Low Voltage Inhibit" circuit indicates that out-
RESET
5
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
