DS9535A Datasheet, PDF (17/18 Pages) Richtek Technology Corporation – High Efficiency Switching Mode Battery Charge

Layout Consideration
Switch rise and fall times are under 20ns for maximum
efficiency. To prevent radiation, the SW pin, the rectifier
Schottky diode D1 and input bypass capacitor leads
should be kept as short as possible. A ground plane
should be used under the switching circuitry to prevent
inter-plane coupling and to act as a thermal spreading
path. Note that the rectifier Schottky diode D1 is
probably the most heat dissipating device in the
charging system. The voltage drop on a 2A Schottky
diode can be 0.5V. With 50% duty cycle, the power
RT9535A
dissipation can go as high as 0.5W. Expanded traces
should be used for the diode leads for low thermal
resistance. Another large heat dissipating device is
probably the inductor. The fast switching high current
ground path including the MOSFETs, D1 and input
bypass capacitor C2 should be kept very short. Another
smaller input bypass (1F ceramic or larger paralleled
with CIN) should be placed to VIN pin and GND pin as
close as possible.
Input capacitor and C7 must
be placed as close to
the IC as possible.
Input Power, V_IN
Place these power components as
close to the SW pin as possible.
D4
GND
SW
C7
CIN
C1
C8
RB
D2
BOOT
C2
D3
VHH
16 15 14 13
VIN ^{R1 EN} 1
C5
SS ₂
12 SW
11 _PGND
C3
R3
R4
C4
R5
ISET ₃
VC ₄
GND 17
10 ^{SNSH RS1}
9 ^{SNSL RS3}
RSH
RSL
5 6 78
C6
Locate the compensation components to
the SS/VC/ISET pin as close as possible.
NTC
R6
C11
C10
R7
V5V
VBATTH
RF2
RF1
C10 and C11 must be
placed as close to the IC as
possible.
Locate the compensation components to
the NTC/VFB pin as close as possible.
D1
L1
RS2
GND
CBATT
VBATT
Figure 2. PCB Layout Guide
Copyright © 2016 Richtek Technology Corporation. All rights reserved.
DS9535A-04 February 2016
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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