S-1702 Datasheet, PDF (26/45 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
3. Detector block
3. 1 Basic operation
Figure 28 shows a block diagram of the detector block.
SENSE
VIN
V_SENSE
V_IN
Current
supply
R_a
V_ref
+
−
R_b
Delay ^VDOUT Output
circuit
circuit
VDOUT
CD
C_D
VSS
V_SS V_SS
N₁
R_c
Figure 28
(1) When the SENSE voltage (VSENSE) is the release voltage (+VDET) or more, the VDOUT pin outputs “H”.
((1) in Figure 29)
In this case, the transistor (N1) is off and the input voltage to the comparator is ^{(Rb + Rc) • VSENSE} .
R_a + R_b + R_c
(2) Although the SENSE voltage (VSENSE) drops to the release voltage (+VDET) or less, the VDOUT pin outputs
“H” when the SENSE voltage (VSENSE) is the detection voltage (−VDET) or more.
If the SENSE voltage (VSENSE) is the detection voltage (−VDET) or less (refer to point A in Figure 29), the
VDOUT pin outputs “L” ((2) in Figure 29).
The transistor (N1) is turned on and the input voltage to the comparator is ^{Rb • VSENSE} .
R_a + R_b
(3) If the VIN input voltage (VIN) further drops to the lowest operating voltage of the S-1702 Series, the VDOUT
pin is sets in high impedance.
If the VDOUT pin is pulled up to the regulator output voltage (VOUT), the VDOUT pin outputs VOUT (“H”) ((3)
in Figure 29).
(4) If the VIN input voltage (VIN) rises to the lowest operating voltage or more, the VDOUT pin outputs “L”.
Although the SENSE voltage (VSENSE) excceds the detection voltage (−VDET), it is the release voltage
(+VDET) or less, the VDOUT pin outputs “L” ((4) in Figure 29).
(5) If the SENSE voltage (VSENSE) rises to the release voltage (+VDET) or more (see point B in Figure 29), the
VDOUT pin outputs “H”. The VDOUT pin outputs “H” after it is delayed for tD by the delay circuit ((5) in
Figure 29).
In the S-1702 Series, the detection voltage (VDOUT) can be set within the range of 1.3 V to 5.2 V (operating voltage
range: VIN = 0.8 V to 6.5 V).
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