S-1702 Datasheet, PDF (20/45 Pages) Seiko Instruments Inc – Built-in overcurrent protection circuit

SUPER-LOW CURRENT CONSUMPTION 150 mA VOLTAGE REGULATOR WITH BUILT-IN HIGH-ACCURACY VOLTAGE DETECTOR AND RESET INPUT FUNCTION
S-1702 Series
Rev.2.2_01
2. 6 Oscillation
In applications where a resistor is connected to the input side (Figure 22), the through-type current which is
generated when the detector output voltage (VDOUT) goes from low to high (release) causes a voltage drop equal
to Through-type current × Input resistance across the resistor. When the input voltage drops below the detection
voltage as a result, the detector output voltage (VDOUT) goes from high to low. In this state, the through-type
current stops, its resultant voltage drop disappears, and the detector output voltage (VDOUT) goes from low to high.
The through-type current is then generated again, a voltage drop appears, and repeating the process finally
induces oscillation.
VIN
R_a
V_IN
R_b
S-1702
VD
block
VDOUT
VSS
Figure 22 Example of Bad Implementation of Detection Voltage Changer
2. 7 Detection voltage temperature characteristics
The shaded area in Figure 23 is the range where −VDET varies within the operation temperature range when the
detection voltage temperature coefficient is ±100 ppm/°C (Refer to *7 of Table 7 for how to calculate the
temperature change of the detection voltage [mV/°C]).
Example of −V_DET = 3.0 V typ. product
−V_DET [V]
+0.30 mV/°C
3.000
−0.30 mV/°C
−40
+25
+85 Ta [°C]
Figure 23
2. 8 Release voltage temperature characteristics
The temperature change
Δ + VDET
ΔTa
of the release voltage is calculated by the temperature change
of the detection voltage as follows:
Δ − VDET
ΔTa
Δ + VDET
ΔTa
=
+ VDET
− VDET
×
Δ
− VDET
ΔTa
The temperature changes of the release voltage and the detection voltage consequently have the same sign.
2. 9 Hysteresis voltage temperature characteristics
The temperature change of the hysteresis voltage is expressed as
Δ + VDET
ΔTa
−
Δ
− VDET
ΔTa
and is calculated as follows:
Δ + V DET
Δ Ta
−
Δ
− V DET
Δ Ta
=
V HYS
− V DET
×
Δ
− V DET
Δ Ta
20