FOSLINK FSP3112LAD

DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
FSP3112
„
FEATURES
„
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High Efficiency : Up to 96%
1.5MHz Constant Frequency Operation
600mA Output Current at VIN=3.0V
Very Low Quiescent Current of 500µA
No Schottky Diode Required
Low RDS(ON) Internal Switches: 0.35Ω
0.6V reference allows low Output Voltage
Current Mode Operation for excellent line and
load transient Response
Short-Circuit &Thermal Fault Protection
<1µA Shutdown Current
Power-on Reset Output
Externally Synchronized Oscillator
Small Thermally Enhanced MSOP10 and DFN10
Packages
The FSP3112 is a dual channel high efficiency
monolithic synchronous step down current mode
DC-DC converter operating at 1.5MHz constant
frequency. The device integrates a main switch and a
synchronous rectifier for high efficiency without an
external Schottky diode for each of the channels. The
FSP3112 can operate from a 2.5V to 5.5V input voltage
and is ideal for powering portable equipment that runs
from a single cell lithium-Ion (Li+) battery. It can supply
600mA output current for each channel and can also
run at 100% duty cycle for low dropout operation,
extending battery life in portable system. For FSP3112,
Pulse Skipping Mode operation at light loads provides
very low output ripple voltage for noise sensitive
applications.
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„
APPLICATIONS
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Portable Media Players
Digital Still Cameras
Cellular Telephones
PDAs
Wireless and DSL modems
„
PIN CONFIGURATION
GENERAL DESCRIPTION
(Top View)
(Top View)
VFB1 1
10 VFB2
VFB1 1
RUN1 2
9 RUN2
RUN1 2
VIN 3
11
EXPOSED PAD
9 RUN2
11
EXPOSED PAD
8 POR
VIN 3
SW1 4
7 SW2
SW1 4
7 SW2
GND 5
6
GND 5
6
NC
10-Lead (3mm ×3mm) Plastic DFN
Exposed Pad is PGND (Pin 11)
Must be connected to GND.
1/10
10 VFB2
8 POR
NC
10-Lead Plastic MSOP
Exposed Pad is PGND (Pin 11)
Must be connected to GND.
2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
FSP3112
„
PIN DESCRIPTION
Pin Number
Pin Name
1
VFB1
2
3
4
5
6
7
8
9
RUN1
VIN
SW1
GND
NC
SW2
POR
RUN2
10
VFB2
11
EXPOSED PAD
„
Pin Function
Channel 1 output feedback. It receives the feedback voltage from the
external resistive divider across the output.
Channel 1 Enable
Power Supply
Channel 1 power switch output
Ground
No Connection
Channel 2 power switch output.
Power On Reset.
Enable Pin of Channel 2.
Channel 2 output feedback. It receives the feedback voltage from the
external resistive divider across the output.
Power Ground. It must be connect to ground properly.
BLOCK DIAGRAM
SLOPE.COMP
Regulator 1
ISENCE
3
VIN
+
-
600mV
EA
+
Q
-
1
VFB1
ICOMP
-
S
_Q
PWM
LOGIC
NON.
OVERLAP
CONTROL
R
+
4
SW1
OVDET
650mV
+
ICMP
+
-
2
RUN1
9
RUN2
10
VFB2
2/10
BANDGAP
REFERENCE
OSC
8
POR
POR
COUNTER
7
SW2
REGULATOR 2(The same structure as regulator 1)
2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
FSP3112
„
ABSOLUTE MAXIMUM RATINGS (NOTE 1)
Parameter
Rating
Unit
Input Supply Voltage
-0.3 to +6
V
RUN1, RUN2
-0.3 to VIN+0.3
V
VFB1, VFB2 Voltages
-0.3 to VIN+0.3
V
SW1, SW2 Voltages
-0.3 to VIN+0.3
V
POR Voltages
-0.3 to +6
V
Peak SW1,SW2 Sink and Source Current
1.5
A
-40 to +85
Operating Temperature Range
℃
+125
Junction Temperature (Note 2)
℃
-65 to 150
Storage Temperature Range
℃
+300
Lead Temperature (soldering, 10 sec.)
℃
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula:
TJ=TA+PD×θJA
„
ELECTRICAL CHARACTERISTICS (NOTE 3)
(VIN=VRUN=3.6V, TA=25℃, Test circuit of Figure 1, Unless otherwise noted)
Parameter
Input Voltage Range
Input DC Supply Current
Active Mode
Shutdown Mode
Regulated Feedback Voltage
Feedback Pin Input Current
Reference Voltage Line Regulation
Output Voltage Line Regulation
Output Voltage Load Regulation
Maximum Output Current
Oscillator Frequency
RDS(ON) of P-CH MOSFET
RDS(ON) of N-CH MOSFET
Peak Inductor Current
SW Leakage
RUN Threshold
RUN Leakage Current
Condition
VFB1=VFB2=0.5V,
RUN=0V, VIN=4.2V
TA=+25℃, Channel 1 or 2
TA=0℃≤TA≤85℃, Channel 1 or 2
TA=-40℃≤TA≤85℃, Channel 1 or 2
VFB=0.65V
VIN=2.5V to 5.5V
VIN=2.5V to 5.5V, VOUT=1.8V,
IOUT=10mA
VIN=3.6V, IOUT=0 to 600mA,
VIN=3.0V
VFB 1/2= 0.6V
ISW=300mA
ISW=-300mA
VIN=3V,VFB1=VFB2=0.5V,
Duty cycle<35%
VRUN=0V, VSW=0V or 5V, VIN=5V
-40℃≤TA≤85℃
Min.
2.5
0.5880
0.5865
0.5850
Typ.
Max.
5.5
Unit
V
500
0.3
800
2
µA
0.6000
0.6000
0.6000
0.11
0.6120
0.6135
0.6150
±30
0.40
V
V
V
nA
%/V
0.11
0.40
%/V
1.8
0.45
0.45
%/mA
mA
MHz
Ω
Ω
0.0015
600
1.2
1.5
0.35
0.28
1.2
A
µA
±0.01
±1
0.45
1.50
V
µA
±0.1
±1
VFBX Ramping Up
8.5
%
VFBX Ramping Down,
-8.5
%
Power-On Reset Threshold (POR)
Power-On Reset Delay
175
mS
Power-On Reset On-Resistance
100
Ω
Note 3: 100% production test at +25℃. Specifications over the temperature range are guaranteed by design and
characterization.
„
0.3
THERMAL RESISTANCE (NOTE 4)
Package
θJA (℃/W)
MSOP-10 (EXPOSE PAD)
45
DFN-10 (EXPOSE PAD)
45
Note 4: Thermal Resistance is specified with approximately 1 square of 1 oz cooper.
3/10
θJC (℃/W)
10
10
2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
„
TYPICAL PERFORMANCE CHARACTERISTICS
FSP3112
(Test Figure 1 below unless otherwise specified)
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2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
„
5/10
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
FSP3112
2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
„
FSP3112
OPERATION
FSP3112 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve high
efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a fixed
switching frequency, and uses the slope compensated current mode architecture. This Step-Down DC-DC
Converter suppliers 600mA output current at VIN=3V with input voltage range from 2.5V to 5.5V. For FSP3112 with
the Pulse Skipping Mode feature, users can optimize ripple at light load for noise sensitive applications.
„
CURRENT MODE PWM CONTROL
Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for
excellent load and line responses and protection of the internal main switch (P-Ch MOSFET) and synchronous
rectifier (N-Ch MOSFET). During normal operation, the internal P-Ch MOSFET is turned on for a certain time to
ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor
current is above the error voltage. The current comparator, ICOMP, limits the peak inductor current. When the main
switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current
starts to reverse, as indicated by the current reversal comparator, IZERO, or the beginning of the next clock cycle. The
OVDET comparator controls output transient overshoots by turning the main switch off and keeping it off until the
faults is no longer present.
„
PULSE SKIPPING MODE OPERATION
The FSP3112 can automatically switch to Pulse Skipping Mode operation at light load to improve efficiency. In the
Pulse Skipping Mode, the inductor current may reach zero or reverse on each pulse. The PWM control loop will
automatically skip pulses to maintain output regulation. The bottom MOSFET is turned off by the current reversal
comparator, IZERO, and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for
the switching regulator.
„
DROPOUT OPERATION
When the input voltage decreases toward the value of the output voltage, the FSP3112 allows the main switch to
remain on for more than one switching cycle and increases the duty cycle until it reaches 100%.
The duty cycle D of a step-down converter is defined as:
D=TON × f OSC × 100% ≈
VOUT
× 100%
VIN
Where TON is the main switch on time and fOSC is the oscillator frequency.
The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At low
input supply voltage, the RDS(ON) of the P-Channel MOSFET increase, and the efficiency of the converter decreases.
Caution must be exercised to ensure the heat dissipated not to exceed the maximum junction temperature of the IC.
„
MAXIMUM LOAD CURRENT
The FSP3112 will operate with input supply voltages as low as 2.5V, however, the maximum load current decreases
at lower input due to large IR drop on the main switch and synchronous rectifier. The slope compensation signal
reduces the peak inductor current as a function of the duty cycle to prevent sub harmonic oscillations at duty cycles
greater than 50%. Conversely the current limit increases as the duty cycle decreases.
6/10
2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
FSP3112
„
APPLICATION INFORMATION
Fig.1 FSP3112 Typical Application Circuit
SETTING THE OUTPUT VOLTAGE
The external resistor sets the output voltage according to the following equation:
⎛ R2 ⎞
VOUT = 0.6V ⎜1+
⎟
⎝ R1 ⎠
Table 1 ----Resistor select for output voltage setting
VOUT
1.2V
1.5V
1.8V
2.5V
R1(R3)
316K
316K
316K
316K
R2(R4)
316K
474K
634K
1001K
INDUCTOR SELECTION
For most designs, the FSP3112 operates with inductors of 1µH to 4.7µH. Low inductance values are physically
smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived from
the following equation:
L=
VOUT × ( VIN − VOUT )
VIN × ∆I L × f OSC
Where ∆IL is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in
high ripple currents. Choose inductor ripple current approximately 35% of the maximum load current 600mA, or
∆IL=210mA.
For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor is
2.2µH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50mΩ
to 150mΩ range. For higher efficiency at heavy loads (above 200mA), or minimal load regulation (but some transient
overshoot), the resistance should be kept below 100mΩ. The DC current rating of the inductor should be at least
equal to the maximum load current plus half the ripple current to prevent core saturation (600mA+105mA). Table2
lists some typical surface mount inductors that meet target applications for the FSP3112.
7/10
2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
FSP3112
Part #
Sumida
CR43
Sumida
CDRH4D18
Toko
D312C
L (µH)
Max DCR (mΩ)
Rated D.C. Current (A)
Size W×L×H (mm)
14
2.2
3.3
4.7
56.2
71.2
86.2
108.7
2.52
1.75
1.44
1.15
4.5×4.0×3.5
1.5
2.2
3.3
4.7
75
110
162
1.32
1.04
0.84
1.5
2.2
3.3
4.7
120
140
180
240
1.29
1.14
0.98
0.79
4.7×4.7×2.0
3.6×3.6×1.2
INPUT CAPACITOR SELECTION
The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input
capacitor impedance at the switching frequency shall be less than input source impedance to prevent high
frequency switching current passing to the input. A low ESR input capacitor sized for minimum RMS current must be
used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small
temperature coefficients. A 4.7µF ceramic capacitor for most applications is sufficient.
OUTPUT CAPACITOR SELECTION
The output capacitor is requires to keep the output voltage ripple small and to ensure regulation loop stability. The
output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R
dielectrics are recommended due to their low ESR and high ripple current. The output ripple VOUT is determined by:
∆VOUT ≤
„
VOUT × ( VIN − VOUT ) ⎛
⎞
1
× ⎜ ESR +
⎟
VIN × f OSC × L
8 × f OSC × C3 ⎠
⎝
ORDERING INFORMATION
FSP3112XXXX
Package:
MS: MSOP10
L: DFN10
„
Packing:
A: Tape & Reel
Temperature Grade:
D: -40~85℃
MARKING INFORMATION
(1) MSOP10
8/10
Output Voltage:
Blank: ADJ
(2) DFN10
2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
„
FSP3112
PACKAGE INFORMATION
(1) MSOP10
GAGE PLANE
L
0.25
DETAIL A
Symbol
A
A1
A2
b
D
E
e
L
y
θ
9/10
Dimensions In Millimeters
Min.
Max.
1.10
0.05
0.15
0.75
0.95
0.17
0.27
2.90
3.10
4.80
5.00
0.50BSC.
0.40
0.70
0.10
0ο
6ο
Dimensions In Inches
Min.
Max.
0.0433
0.0020
0.0060
0.0295
0.0374
0.0067
0.0106
0.1142
0.1220
0.1890
0.1970
0.0197BSC.
0.0157
0.0276
0.0039
0ο
6ο
2007-7-11
DUAL CHANNEL1.5 MHZ, 600MA SYNCHRONOUS STEP-DOWN CONVERTER
FSP3112
2) DFN10
Symbol
A
A1
A3
E
E2
D
D2
b
L
p
10/10
Min.
0.80
0.00
2.85
1.39
2.85
1.20
0.18
0.30
Dimensions In Millimeters
Nom.
Max.
0.90
1.00
0.02
0.05
0.20REF
3.00
3.15
2.45
3.00
3.15
1.75
0.25
0.30
0.40
0.50
0.50BSC
Min.
0.031
0.000
0.112
0.055
0.112
0.047
0.008
0.012
Dimensions In Inches
Nom.
0.035
0.001
0.008REF
0.118
0.118
0.010
0.016
0.020BSC
2007-7-11
Max.
0.039
0.002
0.124
0.096
0.124
0.069
0.015
0.020