TOBY-R2 series - System integration manual
UBX-16010572 - R10
Design-in
Page 67 of 151
PWM mode operation: it is preferable to select regulators with Pulse Width Modulation (PWM)
mode. While in connected-mode, the Pulse Frequency Modulation (PFM) mode and PFM/PWM
modes transitions must be avoided to reduce noise on VCC voltage profile. Switching regulators
can be used that are able to switch between low ripple PWM mode and high ripple PFM mode,
provided that the mode transition occurs when the module changes status from the
idle/active-modes to connected-mode. It is permissible to use a regulator that switches from the
PWM mode to the burst or PFM mode at an appropriate current threshold.
Output voltage slope: the use of the soft start function provided by some voltage regulators
should be carefully evaluated, as the VCC voltage must ramp from 2.3 V to 2.8 V in less than 4 ms
to switch on the modules by applying VCC supply. The modules can be otherwise switched on by
forcing a low level on the RESET_N pin during the VCC rising edge and then releasing the RESET_N
pin when the VCC supply voltage stabilizes at its proper nominal value.
and
show an example of a high reliability power supply circuit, where the module
VCC input is supplied by a step-down switching regulator capable of delivering maximum current with
low output ripple and with fixed switching frequency in PWM mode operation greater than 1 MHz.
12V
C5
R3
C4
R2
C2
C1
R1
VIN
RUN
VC
RT
PG
SYNC
BD
BOOST
SW
FB
GND
6
7
10
9
5
C6
1
2
3
8
11
4
C7
C8
D1
R4
R5
L1
C3
U1
TOBY-R2 series
71
VCC
72
VCC
70
VCC
GND
Figure 28: Example of high reliability VCC supply application circuit using a step-down regulator
Reference
Description
Part Number - Manufacturer
C1
10
µ
F Capacitor Ceramic X7R 5750 15% 50 V
C5750X7R1H106MB - TDK
C2
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C3
680 pF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71H681KA01 - Murata
C4
22 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1H220JZ01 - Murata
C5
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C6
470 nF Capacitor Ceramic X7R 0603 10% 25 V
GRM188R71E474KA12 - Murata
C7
22
µ
F Capacitor Ceramic X5R 1210 10% 25 V
GRM32ER61E226KE15 - Murata
C8
330
µ
F Capacitor Tantalum D_SIZE 6.3 V 45 m
T520D337M006ATE045 - KEMET
D1
Schottky Diode 40 V 3 A
MBRA340T3G - ON Semiconductor
L1
10
µ
H Inductor 744066100 30% 3.6 A
744066100 - Wurth Electronics
R1
470 k
Resistor 0402 5% 0.1 W
2322-705-87474-L - Yageo
R2
15 k
Resistor 0402 5% 0.1 W
2322-705-87153-L - Yageo
R3
22 k
Resistor 0402 5% 0.1 W
2322-705-87223-L - Yageo
R4
390 k
Resistor 0402 1% 0.063 W
RC0402FR-07390KL - Yageo
R5
100 k
Resistor 0402 5% 0.1 W
2322-705-70104-L - Yageo
U1
Step-Down Regulator MSOP10 3.5 A 2.4 MHz
LT3972IMSE#PBF - Linear Technology
Table 20: Components for high reliability VCC supply application circuit using a step-down regulator