S-1702 Datasheet, PDF (24/45 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. Regulator block
2. 1 Basic operation
Figure 25 shows a block diagram of the regulator block.
The error amplifier compares the reference voltage (Vref) with feedback voltage (Vfb), which is the output voltage
resistance-divided by feedback resistors (Rs and Rf). It supplies the gate voltage necessary to maintain the
constant output voltage which is not influenced by the input voltage and temperature change, to the output
transistor.
The regulator output voltage (VOUT) of the S-1702 Series can be selected from a value between 1.5 V and 5.5 V.
VIN
V_IN
Current
supply
Error amplifier
Vref
−
+
Reference
voltage circuit
VSS
V_SS
*1. Parasitic diode
Output circuit
Output transistor
*1
V_OUT
R_f
V_fb
R_s
Discharge
shunt
circuit
Figure 25
VOUT
2. 2 Output circuit
The output circuit of the regulator block consists of an output transistor and a discharge shunt circuit.
The discharge shunt function is enabled or disabled for the VOUT pin. Refer to “Table 1 Product Types” for
details. The equivalent circuits are shown below.
V_IN
V_IN
*1
V_OUT
R_f
V_fb
VOUT
*1
V_OUT
R_f
V_fb
VOUT
R_s
R_s
V_SS
V_SS V_SS
V_SS V_SS V_SS V_SS
Discharge shunt function: enabled
Discharge shunt function: disabled
*1. Parasitic diode
Figure 26 Equivalent Circuits of VOUT Pin
24