FP6711MSPTR [FITIPOWER]

High-Efficiency, 1-Cell and 2-Cell Boost Converter;
FP6711MSPTR
型号: FP6711MSPTR
厂家: Fitipower    Fitipower
描述:

High-Efficiency, 1-Cell and 2-Cell Boost Converter

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fitipower integrated technology lnc.  
FP6711  
High-Efficiency, 1-Cell and  
2-Cell Boost Converter  
Description  
Features  
The FP6711 is a high efficiency, fixed frequency  
500KHz, current mode PWM boost DC/DC converter  
which could operate from single/dual-cell NiCd,  
NiMH or alkaline battery such as input voltage below  
1V. The converter output voltage can be adjusted  
from 1.8V to maximum 4V by an external resistor  
divider. Besides the converter includes a 0.35Ω  
N-channel MOSFET switch and 0.45Ω P-channel  
synchronous rectifier. So no external Schottky  
diode is required, and it could get better efficiency  
near 94%.  
● Synchronous Rectification: 94% Efficiency  
● Very Low Start-up Voltage at 0.85V  
Automatically Switch to PFM Mode for Improving  
Efficiency at Light Load  
Built-in True Shutdown: Isolation of Load from  
Battery during Shutdown  
● Internal Anti-Ringing Switch across Inductor  
● Low Battery Warning Display  
● Fixed Frequency Operation at 500kHz  
● Very Low Shutdown Current at 1μA  
● Small 10-Pin MSOP Package  
RoHS Compliant  
The converter is based on a fixed frequency, current  
mode, pulse-width-modulation PWM controller that  
goes automatically into PFM mode at light load  
which quiescent current is only 25μA in this mode  
operation.  
Applications  
Handheld Instrument  
Cordless Phone  
Wireless Handset  
GPS Receiver  
MP3  
The converter features a special function that the  
load is completely isolated from the battery during  
shutdown.  
Besides it also has auto-discharge  
function which could discharge the output capacitor  
immediately during shutdown.  
When converter operates into discontinuous mode,  
the internal anti-ringing switch will reduce  
interference and radiated electromagnetic energy.  
The FP6711 is available in a space-saving 10-lead  
MSOP package for portable application.  
Pin Assignments  
Ordering Information  
FP6711□□□  
MS Package (MSOP-10)  
TR: Tape/Reel  
1
2
3
4
5
10  
9
EN  
COMP  
FB  
LBO  
LBI  
P: Green  
G: Green  
8
ADEN  
SW  
Package Type  
MS: MSOP-10  
7
GND  
VOUT  
6
VIN  
Figure 1. Pin Assignment of FP6711  
FP6711-1.4-DEC-2011  
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FP6711  
Typical Application Circuit  
L1  
10µH  
SW  
VIN  
VOUT  
LBO  
VOUT  
COUT  
VIN  
R5  
R1  
R2  
22µF  
R3  
CIN  
10µF  
LBI  
Low Battery  
Warning  
FP6711  
GND  
ADEN  
EN  
FB  
ON  
R4  
COMP  
OFF  
RC  
CC  
680K  
100P  
Figure 2. Typical Application Circuit of FP6711  
Functional Pin Description  
Pin Name  
Pin Function  
EN  
COMP  
FB  
Chip-enable input. Pull the pin high to enable IC. Pull the pin low to shutdown IC.  
The gm error amplifier output. A frequency compensation network is connected from this pin to ground to  
compensate the loop.  
The feedback input for adjusting output voltage. This pin connects resistor divider that output voltage could be  
adjusted from 1.8V to 4V. The feedback voltage is typical at 0.5V.  
GND  
VOUT  
VIN  
Ground pin  
Output voltage pin  
Input voltage pin  
SW  
Switch input pin which is connected to inductor  
Auto-discharge enable input pin. The auto-discharge function will be enabled when this pin is connected to logic  
high. It will be disabled when this pin is connected to logic low.  
ADEN  
Low battery detector input. A low battery warning signal is generated at LBO when the voltage on LBI drops  
below the threshold voltage of 500mV. Connect LBI to GND or VIN when low battery detector function is not  
used. Don’t leave this pin floating.  
LBI  
Open drain low battery detector output. This Pin will be pulled low when the voltage on LBI drops below the  
threshold voltage of 500mV. An external pull-up resistor has to be connected between LBO and VOUT.  
LBO  
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FP6711  
Block Diagram  
ADEN  
VIN  
SW  
PMOS  
VOUT  
ANTIRING  
I2  
On/Off  
Control  
EN  
NMOS  
PFM  
Control  
Body-Diode  
Switch  
Anti-Reverse  
Comparator  
Isense/current limit  
Ramp generator  
OSC  
PWM  
Control  
Logic  
LBI  
COMP  
FB  
Error Amp  
Bandgap  
Reference  
UVLO  
LBO  
VREF  
VIN  
GND  
Figure 3. Block Diagram of FP6711  
COMP  
Absolute Maximum Ratings  
Supply Input Voltage (VIN ,VOUT, EN, LBI, COMP, FB, ADEN, LBO) ------------------------------ -0.3V to +4V  
● SW Voltage (SW) ------------------------------------------------------------------------------------------------ -0.3V to +7V  
+630mW  
Power Dissipation @TA=25C, MSOP-10 (PD) -----------------------------------------------------------  
Package Thermal Resistance, MSOP-10 (θJA) ----------------------------------------------------------- +160C/W  
Maximum Junction Temperature (TJ) -----------------------------------------------------------------------  
+150C  
Storage Temperature Range (T ) ----------------------------------------------------------------------------  
-65C to +150C  
S
Lead Temperature (Soldering, 10 sec.) (TLEAD) -----------------------------------------------------------  
+260C  
Note 1Stresses beyond those listed under “Absolute Maximum Ratings" may cause permanent damage to the device.  
Recommended Operating Conditions  
● Input Voltage (VIN) ----------------------------------------------------------------------------------------------- +0.85V to VOUT  
● Operating Temperature Range (TOPR) ----------------------------------------------------------------------  
-40C to +85C  
FP6711-1.4-DEC-2011  
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FP6711  
Electrical Characteristics  
(VIN=1.2V, EN=VIN, TA=25C, unless otherwise specified)  
Parameter  
Symbol  
Conditions  
Min  
Typ  
Max  
Unit  
V
Start-up Voltage  
VST  
IOUT =1mA  
IOUT =1mA  
VFB>0.7V  
0.85  
Output Voltage Range  
Quiescent Current (No Switching)  
Switch Current Limit (Note2)  
Feedback Voltage  
VOUT  
IQ  
1.8  
4
V
25  
1
40  
µA  
A
ILIM  
VOUT =3.3V  
VFB  
490  
420  
500  
500  
85  
510  
780  
mV  
kHz  
%
Oscillation Frequency  
fOSC  
DMAX  
Maximum Duty Cycle  
NMOS Switch ON Resistance  
(Note2)  
PMOS Switch ON Resistance  
(Note2)  
RDS(ON) VOUT =3.3V  
RDS(ON) VOUT =3.3V  
0.35  
0.45  
0.3  
0.1  
300  
Ω
Ω
Line Regulation  
Load Regulation  
VIN =2V to 2.4V Io =100mA  
%
VLINE  
VIN =2V IOUT =50 to 100mA  
%
VLOAD  
Auto-Discharge Switch Resistance  
(Note2)  
Residual Output Voltage after  
Discharge  
400  
0.4  
Ω
ADEB =VIN EN =GND  
VLBI voltage decreasing  
V
LBI Voltage Threshold  
LBI Input Hysteresis  
VLBI  
480  
500  
10  
520  
mV  
mV  
µA  
V
LBI Input Current  
0.1  
1
LBO Output Low Voltage  
LBO Output Leakage Current  
FB Input Bias Current  
VLBO  
VLBI =0V, VOUT =3.3V  
0.2  
VLBI =650mV, VLBO =VO  
0.1  
0.1  
1
1
µA  
µA  
V
I(FB)  
VIL  
EN/ADEN Input Low Voltage  
EN/ADEN Input High Voltage  
EN/ADEN Input Current  
0.8V<VIN<5V  
VIN0.1  
VIH  
0.8V<VIN<5V  
V
VIN0.9  
EN/ADEN =GND or VIN  
EN =0V, ADEN= VIN  
0.1  
1
1
5
µA  
µA  
C  
C  
Shutdown Current from Power  
Source  
IOFF  
TSD  
150  
20  
Over-Temperature Protection  
(Note2)  
Δ TSD  
Hysteresis  
Note 2The specification is guaranteed by design, not production tested.  
FP6711-1.4-DEC-2011  
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FP6711  
Typical Performance Curves  
700  
600  
500  
400  
300  
200  
100  
0
600  
500  
400  
300  
200  
100  
VOUT=3.3V  
VOUT=2.5V  
0.9  
1.2  
1.5  
1.8  
2.1  
2.4  
1.0  
1.5  
2.0  
2.5  
3.0  
Input Voltage(V)  
Input Voltage(V)  
Figure 4. Maximum Output Current vs. Input Voltage  
Figure 5. Maximum Output Current vs. Input Voltage  
100  
100  
VBAT=1.2V  
VBAT=1.2V  
90  
90  
80  
70  
60  
50  
40  
30  
20  
10  
VOUT=2.5V  
VOUT=3.3V  
80  
70  
60  
50  
40  
30  
20  
10  
0.1  
1
10  
100  
1000  
0.1  
1
10  
100  
1000  
IOUT Output Current(mA)  
IOUT Output Current(mA)  
Figure 6. Efficiency vs. Output Current  
Figure 7. Efficiency vs. Output Current  
100  
90  
80  
70  
60  
50  
40  
30  
20  
10  
100  
90  
80  
70  
60  
50  
40  
30  
20  
10  
VBAT=2.5V  
VOUT=3.3V  
VBAT=1.5V  
VOUT=3.3V  
0.1  
1
10  
100  
1000  
0.1  
1
10  
100  
1000  
IOUT Output Current(mA)  
IOUT Output Current(mA)  
Figure 8. Efficiency vs. Output Current  
FP6711-1.4-DEC-2011  
Figure 9. Efficiency vs. Output Current  
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FP6711  
Typical Performance Curves (Continued)  
3.50  
100  
VIN=1.2V  
90  
IO=10mA  
80  
IO=100mA  
3.25  
70  
IO=150mA  
60  
50  
3.00  
0.5  
1.0  
1.5  
2.0  
2.5  
3.0  
3.5  
0.1  
1
10  
100  
1000  
Output Current (mA)  
Input Voltage (V)  
Figure 10. Efficiency vs. Input Voltage (VOUT=3.3V)  
Figure 11. Output voltage vs. Output Current  
50  
45  
40  
35  
30  
25  
20  
15  
10  
2.75  
2.50  
2.25  
VIN=1.2V  
TA=850C  
TA=250C  
TA=-400C  
1.0  
1.5  
2.0  
2.5  
3.0  
0.1  
1
10  
100  
1000  
Output Current (mA)  
Input Voltage(V)  
Figure 12. Output voltage vs. Output Current  
Figure 13. Quiescent Current vs. Input Voltage  
0.520  
0.515  
0.510  
0.505  
0.500  
0.495  
0.490  
0.485  
0.480  
750  
700  
650  
600  
550  
500  
450  
400  
350  
-40  
-20  
0
20  
40  
60  
80  
-40  
-20  
0
20  
40  
60  
80  
Temperature (0C)  
Temperature (0C)  
Figure 14. Feedback Voltage vs. Temperature  
FP6711-1.4-DEC-2011  
Figure 15. Oscillator Frequency vs. Temperature  
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FP6711  
Typical Performance Curves (Continued)  
3.30  
3.25  
3.20  
3.15  
3.10  
3.05  
3.00  
2.95  
2.90  
2.85  
2.80  
5
4
3
2
1
0
V
IN=1.5V  
VOUT=3.0V  
IO=10mA  
TA=850C  
TA=250C  
TA=-400C  
1.2  
1.5  
1.8  
2.1  
2.4  
2.7  
3.0  
-40  
-20  
0
20  
40  
60  
80  
Temperature (0C)  
Input Voltage (V)  
Figure 16. Output Voltage vs. Temperature  
Figure 17.Shutdown Supply Current vs. Input Voltage  
CH1: VSW ,CH2: VOUT ,CH4: IL (VIN=1.5V, VOUT=3.3V, IOUT=20mA)  
CH1: VSW ,CH2: VOUT ,CH4: IL (VIN=1.2V, VOUT=3.3V, IOUT=100mA)  
Figure 18. Dynamic Test  
Figure 19. Dynamic Test  
CH2: VOUT ,CH4: IOUT (VIN=2V, VOUT=3V, IOUT=50mA 100mA)  
CH1: VIN ,CH2: VOUT (VIN=1.2V~1.8V, VOUT=3.3V, IOUT=50mA)  
Figure 20. Load Transient Response  
Figure 21. Line Transient Response  
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FP6711  
Typical Performance Curves (Continued)  
VOUT  
VSW  
SHDN  
IIN  
VOUT  
VIN=1.5V, VOUT=3.3V  
IOUT=10mA100mA (PFMPWM)  
IL  
SW  
Figure 22. Load Transient Response  
Figure 23. Converter Start-up Time after Enable  
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FP6711  
Application Information  
Controller Circuit  
PFM Mode  
The device is based on a current-mode control  
The FP6711 is designed for high efficiency over a  
wide output current range. Even at light load, the  
efficiency stays high because the switching losses  
of the converter are minimized by effectively  
reducing the switching frequency. The controller  
will enter a power saving mode if certain conditions  
are met. In this mode, the controller only switches  
on the transistor if the output voltage trips below a  
set threshold voltage. It ramps up the output  
voltage with one or several pulses, and goes again  
into PFM mode once the output voltage exceeds a  
set threshold voltage.  
topology and uses  
a
constant frequency  
pulse-width modulator to regulate the output  
voltage. The controller limits the current through  
the power switch on a pulse by pulse basis. The  
current sensing circuit is integrated in the device;  
therefore, no additional components are required.  
Due to the nature of the boost converter topology  
used here, the peak switch current is the same as  
the peak inductor current, which will be limited by  
the integrated current limiting circuits under normal  
operating conditions.  
The control loop must be externally compensated  
with an R-C network connected to the COMP pin.  
Device Enable  
The device will be shut down when EN is set to  
GND. In this mode, the regulator stops switching,  
all internal control circuitry including the low-battery  
comparator will be switched off, and the load is  
disconnected from the input (as described in above  
synchronous rectifier section). This also means  
that the output voltage may drop below the input  
voltage during shutdown.  
Synchronous Rectifier  
The device integrates an N-channel and a P-  
channel MOSFET transistor to realize  
a
synchronous rectifier. There is no additional  
Schottky diode required. Because the device  
uses a integrated low RDS(ON) PMOS switch for  
rectification, the power conversion efficiency  
reaches 94%.  
The device is put into operation when EN is set  
high. During start-up of the converter, the duty  
cycle is limited in order to avoid high peak currents  
drawn from the battery. The limit is set internally  
by the current limit circuit and is proportional to the  
voltage on the COMP pin.  
A special circuit is applied to disconnect the load  
from the input during shutdown of the converter.  
In conventional synchronous rectifier circuits, the  
backgate diode of the high-side PMOS is forward  
biased in shutdown and allows current flowing from  
the battery to the output. This device, however,  
uses a special circuit to disconnect the backgate  
diode of the high-side PMOS and so, disconnects  
the output circuitry from the source when the  
regulator is not enabled (EN = low).  
Under-Voltage Lockout  
Under-voltage lockout function prevents the device  
from starting up if the supply voltage on VBAT is  
lower than approximately 0.7V. This under-voltage  
lockout function is implemented in order to prevent  
the malfunctioning of the converter. When the  
battery is being discharged, the device will  
automatically enter the shutdown mode if the  
voltage on VBAT drops below approximately 0.7V.  
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FP6711  
Application Information (Continued)  
Auto-Discharge  
Adjustable Output Voltage  
The auto-discharge function is useful for  
applications where the supply voltage of a µC, µP,  
or memory has to be removed during shutdown in  
order to ensure a defined state of the system.  
The accuracy of the output voltage is determined by  
the accuracy of the internal voltage reference, the  
controller topology, and the accuracy of the external  
resistor. The reference voltage has an accuracy of  
± 4%.  
The controller switches between fixed  
frequency and PFM mode, depending on load  
current. The tolerance of the resistors in the  
feedback divider determines the total system  
accuracy.  
The auto-discharge function will be enabled when  
the ADEN is set high; and it will be disabled when  
the ADEN is set to GND.  
When the  
auto-discharge function is enabled, the output  
capacitor will be discharged after the device is shut  
down by setting EN to GND. The capacitors  
connected to the output are discharged by an  
integrated switch of 300Ω, hence the discharge  
time depends on the total output capacitance. The  
residual voltage on VOUT is less than 0.4V after  
auto-discharge.  
Design Procedure  
The FP6711 boost converter family is intended for  
systems that are powered by a single-cell NiCd or  
NiMH battery with a typical terminal voltage  
between 0.9V to 1.6V. It can also be used in  
systems that are powered by two-cell NiCd or NiMH  
batteries with a typical stack voltage between 1.8V  
to 3.2V. Additionally, single or dual-cell, primary  
and secondary alkaline battery cells can be the  
power source in systems where the FP6711 is used.  
The resistive divider scales down the battery  
voltage to a voltage level of 500mV, which is then  
compared to the LBI threshold voltage. The LBI  
pin has a built-in hysteresis of 10mV. See the  
application section for more details about the  
programming of the LBI threshold.  
(1) Programming the Output Voltage  
If the low-battery detection circuit is not used, the  
LBI pin should be connected to GND (or to VBAT)  
and the LBO pin can be left unconnected. Do not  
let the LBI pin float.  
The output voltage of the FP6711 can be  
adjusted with an external resistor divider. The  
typical value of the voltage on the FB pin is  
500mV in fixed frequency operation.  
The  
maximum allowed value for the output voltage is  
3.3V. The current through the resistive divider  
should be about 100 times greater than the  
current into the FB pin. The typical current into  
the FB pin is 0.01µA, and the voltage across R4  
is typically 500mV. Based on those two values,  
the recommended value for R4 is in the range of  
500kΩ in order to set the divider current at 1µA.  
From that, the value of resistor R3, depending on  
the needed output voltage (VO), can be  
calculated using Equation 1.  
Low-Battery Detector Circuit (LBI and LBO)  
The low-battery detector circuit is typically used to  
supervise the battery voltage and generate an error  
flag when the battery voltage drops below user-set  
threshold voltage. The function is active only  
when the device is enabled. When the device is  
disabled, the LBO pin will be high impedance. The  
LBO pin goes active low when the voltage on the  
LBI pin decreases below the set threshold voltage  
of 500 mV ±15 mV, which is equal to the internal  
reference voltage. The battery voltage, at the  
detection circuit switches, can be programmed with  
a resistive divider connected to the LBI pin.  
VO  
VO  
R3 R4(  
-1) 500k(  
.....(1)  
-1)  
VFB  
500 mV  
Anti-Ringing Switch  
The device integrates a circuit which removes the  
ringing that typically appears on the SW node when  
the converter enters the discontinuous current  
mode. In this case, the current through the  
inductor ramps to zero and the integrated PMOS  
switch turns off to prevent a reverse current from  
the output capacitors back to the battery. Due to  
remaining energy that is stored in parasitic  
components of the semiconductors and the  
inductor, a ringing on the SW pin is induced. The  
integrated anti-ringing switch clamps this voltage  
internally to VBAT; therefore, dampens this ringing.  
FP6711-1.4-DEC-2011  
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FP6711  
Application Information (Continued)  
In this example, the desired inductor has the value  
of 12µH. With this calculated value and currents,  
it is possible to choose a suitable inductor. Care  
must be taken that load transients and losses in the  
circuit can lead to higher currents. Also, the  
losses in the inductor caused by magnetic  
hysteresis losses and copper losses are a major  
parameter for total circuit efficiency.  
(2) Programming the Low Battery Comparator  
Threshold Voltage  
The current through the resistive divider should  
be about 100 times greater than the current into  
the LBI pin. The typical current into the LBI pin  
is 0.01µA; the voltage across R2 is equal to the  
reference voltage that is generated on-chip,  
which has a value of 500mV±15mV.  
The  
recommended value for R2 is therefore in the  
range of 500 kΩ. From that, the value of  
resistor R1, depending on the desired minimum  
battery voltage VBAT, can be calculated using  
Equation 2.  
(4) Capacitor Selection  
The major parameter necessary to define the  
output capacitor is the maximum allowed output  
voltage ripple of the converter. This ripple is  
determined by two parameters of the capacitor, the  
capacitance and the ESR.  
It is possible to  
VBAT  
VREF  
VBAT  
..(2)  
-1)  
R1R2(  
-1) 500k(  
calculate the minimum capacitance needed for the  
defined ripple, supposing that the ESR is zero, by  
using Equation 4.  
500mV  
For example, if the low-battery detection circuit  
should flag an error condition on the LBO output  
pin at a battery voltage of 1V, a resistor in the  
range of 500kΩ should be chosen for R1. The  
output of the low battery comparator is a simple  
open-drain output that goes active low if the  
battery voltage drops below the programmed  
threshold voltage on LBI. The output requires a  
pull-up resistor with a recommended value of  
1MΩ, and should only be pulled up to the VO. If  
not used, the LBO pin can be left floating or tied  
to GND.  
IOUT × (VOUT - VBAT  
)
..(4)  
CMIN  
=
f × ΔV× VOUT  
Parameter f is the switching frequency and V is  
the maximum allowed ripple.  
With a chosen ripple voltage of 15mV, a minimum  
capacitance of 10 µF is needed. The total ripple is  
larger due to the ESR of the output capacitor.  
This additional component of the ripple can be  
calculated using Equation 5.  
ΔVESR =IOUT × RESR ..(5)  
(3) Inductor Selection  
A boost converter normally requires two main  
passive components for storing energy during  
the conversion. A boost inductor is required and  
a storage capacitor at the output. To select the  
boost inductor, it is recommended to keep the  
possible peak inductor current below the current  
limit threshold of the power switch in the chosen  
configuration.  
An additional ripple of 30mV is the result of using a  
tantalum capacitor with a low ESR of 300mΩ. The  
total ripple is the sum of the ripple caused by the  
capacitance and the ripple caused by the ESR of  
the capacitor. In this example, the total ripple is  
45mV. It is possible to improve the design by  
enlarging the capacitor or using smaller capacitors  
in parallel to reduce the ESR or by using better  
capacitors with lower ESR, like ceramics. For  
example, a 10µF ceramic capacitor with an ESR of  
50mΩ is used on the evaluation module (EVM).  
Tradeoffs must be made between performance and  
costs of the converter circuit.  
The second parameter for choosing the inductor  
is the desired current ripple in the inductor.  
Normally, it is advisable to work with a ripple of  
less than 20% of the average inductor current.  
A smaller ripple reduces the magnetic hysteresis  
losses in the inductor, as well as output voltage  
ripple and EMI. But in the same way, regulation  
time at load changes rises. In addition, a larger  
inductor increases the total system cost. With  
those parameters, it is possible to calculate the  
value for the inductor by using Equation 3.  
A 10µF input capacitor is recommended to improve  
transient behavior of the regulator. A ceramic or  
tantalum capacitor with a 100nF in parallel placed  
close to the IC is recommended.  
VBAT × (VOUT - VBAT  
)
..(3)  
L =  
ΔIL × f × VOUT  
Parameter f is the switching frequency and ΔIL is  
the ripple current in the inductor, i.e, 20% x IL.  
FP6711-1.4-DEC-2011  
11  
fitipower integrated technology lnc.  
FP6711  
Application Information (Continued)  
(5) Compensation of the Control Loop  
Thermal Information  
An R/C network must be connected to the COMP  
pin in order to stabilize the control loop of the  
converter. Both the pole generated by the  
inductor L1 and the zero caused by the ESR and  
capacitance of the output capacitor must be  
compensated. The network shown in Figure 24  
satisfies these requirements.  
The maximum junction temperature (TJ) of the  
FP6711 devices is recommended to 125°C. The  
thermal resistance of the 10-pin MSOP package is  
JA=160°C/W. Specified regulator operations are  
assured to a maximum ambient temperature (TA) of  
70°C. Therefore, the maximum power dissipation  
is about 340mW. More power can be dissipated if  
the maximum ambient temperature of the  
application is lower.  
VOUT  
0.5V  
TJ(MAX) - TA  
125C - 70C  
160C/W  
R3  
ERROR  
AMP  
PD(MAX)  
340mW  
JA  
8
R4  
Layout Considerations  
9
CC  
Rc  
As for all switching power supplies, the layout is an  
important step in the design, especially at high peak  
currents and high switching frequencies. If the  
layout is not carefully done, the regulator could  
show stability problems as well as EMI problems.  
Therefore, use wide and short traces for the main  
current path as indicated in bold in Figure 25. The  
input capacitor, output capacitor and the inductor  
should be placed as close to the IC as possible.  
Use a common ground node as shown in Figure 25  
to minimize the effects of ground noise. The  
compensation circuit and the feedback divider  
should be placed as close to the IC as possible. To  
layout the control ground, it is recommended to use  
short traces as well, separated from the power  
ground traces. Connect both grounds close to the  
ground pin of the IC as indicated in the layout  
diagram in Figure25. This avoids ground shift  
problems, which can occur due to superimposition  
of power ground current and control ground current.  
Figure 24. Compensation of Control Loop  
Resistor RC and capacitor CC depend on the  
chosen inductance. The equation for the loop  
dynamics is shown as below :  
1
HZ  
fZER01  
=
2 x  
π
x Rc x CC  
The FP6711 uses current mode control with  
internal adaptive slope compensation. Current  
mode control eliminates the 2nd order filter due to  
the inductor and output capacitor exhibited in  
voltage mode controllers and simplifies it to a  
single-pole filter response.  
L1  
VOUT  
SW  
R5  
OUTPUT  
VBAT  
LBI  
LBO  
FB  
LBO  
Battery  
C4  
R3  
R1  
R2  
C1  
FP6711  
RC  
COMP  
GND  
ADEN  
EN  
R4  
CC  
Figure 25. Layout Diagram  
FP6711-1.4-DEC-2011  
12  
fitipower integrated technology lnc.  
FP6711  
Outline Information  
MSOP-10 Package (Unit: mm)  
DIMENSION IN MILLIMETER  
SYMBOLS  
UNIT  
MIN  
0.75  
0.00  
0.75  
0.17  
2.90  
4.80  
2.90  
0.40  
0.40  
MAX  
1.10  
0.15  
0.95  
0.33  
3.10  
5.00  
3.10  
0.60  
0.80  
A
A1  
A2  
B
D
E
E1  
e
L
Carrier dimensions  
Life Support Policy  
Fitipower’s products are not authorized for use as critical components in life support devices or other medical systems.  
FP6711-1.4-DEC-2011  
13  

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