LOW DROPOUT CMOS VOLTAGE REGULATOR
S-818 Series
Rev.1.2
Technical Terms
1. Low dropout voltage regulator
The low dropout voltage regulator is a voltage regulator having a low dropout voltage characteristic due to the
internal low on-resistance transistor.
2. Output voltage (VOUT)
The accuracy of the output voltage is ensured at ± 2.0% under the specified conditions of input voltage,
output current, and temperature, which differ product by product.
Note:
When the above conditions are changed, the output voltage may vary and go out of the accuracy range of
the output voltage. See the electrical characteristics and characteristic data for details.
3. Line regulations 1 and 2 (∆VOUT1, ∆VOUT2)
Line regulation indicates the input voltage dependence of the output voltage. The value shows how much the
output voltage changes due to the change of the input voltage when the output current is kept constant.
4. Load regulation (∆VOUT3)
Load regulation indicates the output current dependence of output voltage. The value shows how much the
output voltage changes due to the change of the output current when the input voltage is kept constant.
5. Dropout voltage (Vdrop)
Let VIN1 be an input voltage where the output voltage falls to the 98% of the actual output voltage VOUT(E)
when gradually decreasing input voltage. The dropout voltage is the difference between the VIN1 and the
resultant output voltage defined as following equation.
Vdrop = VIN1-[VOUT(E) × 0.98]
6. Temperature coefficient of output voltage [∆VOUT/(∆Ta • VOUT)]
The shadowed area in Figure 6 is the range where VOUT varies in the operating temperature range when the
temperature coefficient of the output voltage is ±100 ppm/°C.
Typical Example of the S-818A28A
OUT
V
[V]
+0.28mV/ C
°
VOUT (E) is a mesured value of
output voltage at 25 C.
OUT
(E)
°
-0.28mV/ C
°
-40
25
Ta [ C]
85
°
Figure 6 Temperature coefficient range of output voltage
A change of output voltage in temperature [mV/°C] is calculated using the following equation.
∆VOUT
∆Ta • VOUT
∆VOUT
∆Ta
[ppm/°C] ÷1000
[mV/°C] = VOUT(S)[V] ×
Specified output voltage
Output voltage temperature coefficient
Change of output voltage in temperatures
6
Seiko Instruments Inc.
SII [ SEIKO INSTRUMENTS INC ]
