S-8540 Datasheet, PDF (20/36 Pages) Seiko Instruments Inc – STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER

STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8540/8541 Series
Rev.3.2_00
„ 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 (R_A, R_B) and a capacitor (C_FB) 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 R_A and R_B.
R_{SEN SE}
L
SENSE
Tr
VIN ^{Power for IC Triangular wave}
oscillation circuit
+
−
EXT
PWM comparator
−
Phase
comp ensation
ci rc ui t
125m V
VOUT
VIN
SD
C_IN
+
PW M, PW M/PFM
switching control
circuit
Error amplifier
−
+
CFB
RA
C_{OU T}
FB
Shutdown s of t start
circuit
VREF=1.0 V
V o lta ge / cu rre n t
VSS
RB
referenc e
One point ground
ON/OFF
V_ON/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
Seiko Instruments Inc.