Service Guide

LTE-A Module Series
EM060K-GL&EM120K-GL_Hardware_Design 28 / 78
D1
TVS
PWR
_
IN
C
8
220 μF
C
11
10 pF
C10
33 pF
C9
100 nF
+
R1
205K
U1
Q1
NPN
R8
47K
R7
4.7K
PWR_EN
R4
182K
PWR_OUT
L1
1.5
μ
H
VIN
VIN
VIN
EN
VSNS
COMP
RT/CLK
SS
PH
PH
PH
BOOT
PWRGD
GND
GND
AGND
VFB
R5
383K
1 %
R6
100K
1 %
C6
100 nF
PWRGD
EP
R2
80.6K
C7
10 nF
R3
10K
C4
10 nF
C5
NM
VFB
C2
100 nF
C3
33 pF
C1
470 μF
+
Figure 5: Reference Circuit for the Power Supply
To avoid corrupting the data in the internal flash, do not cut off the power supply before the module is
completely turned off by pulling down FULL_CARD_POWER_OFF# pin for more than 6.6 s, and do not
cut off power supply directly when the module is working.
3.5.3. Voltage Stability Requirements
The power supply of the module ranges from 3.135 V to 4.4 V. Please ensure that the input voltage will
never drop below 3.135 V, otherwise the module will be powered off automatically. The following figure
shows the maximum voltage drop during radio transmission in 3G/4G networks.
VCC
Burst Transmission
Voltage Ripple
< 100 mV
Voltage Drop
Burst Transmission
3.135 V
Figure 6: Power Supply Limits during Radio Transmission
Ensure the continuous current capability of the power supply is 2.0 A. To decrease the voltage drop, two
bypass capacitors of about 220 µF with low ESR (ESR = 0.7 Ω) should be used. To decrease the power
supply being disturbed, a multi-layer ceramic chip capacitor (MLCC) array also should be used due to
their ultra-low ESR. It is recommended to use four ceramic capacitors (1 µF, 100 nF, 33 pF, 10 pF) for
composing the MLCC array, and to place these capacitors close to VCC pins. The width of VCC trace
should be no less than 2.5 mm. In principle, the longer the VCC trace is, the wider it should be.
In addition, to guarantee the stability of the power supply, please use a TVS with a reverse TVS voltage of
NOTE