S-8540A15FN-IAAT2Z Datasheet, PDF (20/36 Pages) Seiko Instruments Inc – SWITCHABLE SWITCHING REGULATOR CONTROLLER

STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8540/8541 Series
Rev.4.0_01
 Application Circuits
1. External adjustment of output voltage
The output voltage can be adjusted or changed in the output voltage setting range (1.5 to 6.0 V) by
adding external resistors (RA, RB) and a capacitor (CFB) in the S-8540/8541B00AFN and S-
8540/8541D00AFN, as shown in Figure 15. Temperature gradient can be given by inserting a
thermistor in series to RA and RB.
R_SENSE
L
SENSE
Tr
VIN ^{Power for IC Triangular wave}
oscillation circuit
+
−
EXT
PWM comparator
Phase
compensation
circuit
125mV
VOUT
−
V_IN
SD
+
Error amplifier
CFB
RA
C_IN
PWM, PWM/PFM
−
switching control
circuit
+
C_OUT
FB
Shutdown soft start
circuit
V_REF=1.0 V
Voltage/current
VSS
RB
reference
One point ground
ON/OFF
VON/OFF
CVREF
Figure 15
Caution The above connection diagram and constant will not guarantees successful operation.
Perform through evaluation using the actual application to set the constant.
20