Anpec APW7098 Two- phase buck pwm controller with integrated mosfet driver Datasheet

APW7098
Two- Phase Buck PWM Controller with Integrated MOSFET Drivers
Features
•
•
•
•
•
•
General Description
- Fast Load Transient Response
Operate with 8V~13.2VCC Supply Voltage
Selectable External or Internal 0.6V Reference
- ±1.5% Accuracy Over Temperature
Support Single- and Two-Phase Operations
5VCC and Buffered Reference Outputs
8~12V Gate Drivers with Internal Bootstrap
Diode
•
•
Lossless Inductor DCR Current Sensing
Selectable Operation Frequency
•
- 150k/300k/400kHz per Phase
Power-OK Indicator Output
•
•
•
•
•
•
•
•
The APW7098, two-phase PWM control IC, provides a
precision voltage regulation system for advanced graphic
microprocessors in graphics card applications. The
integration of power MOSFET drivers into the controller
IC and reduces the number of external parts for a cost
and space saving power management solution.
The APW7098 uses a voltage-mode PWM architecture,
operating with fixed-frequency, to provides excellent load
transient response. The device uses the voltage across
the DCRs of the inductors for current sensing. Load line
voltage positioning (DROOP), channel-current balance,
and over-current protection are accomplished through
continuous inductor DCR current sensing.
The MODE pin programs single- or two- phase operation.
When IC operates in two-phase mode normally, it can
transfer two-phase mode to single-phase mode at liberty.
Nevertheless, once operates in single-phase mode, the
operation mode is latched. It is required to toggle SS,
REFIN/EN or 5VCC pin to reset the IC. Such feature of the
MODE pin makes the APW7098 ideally suitable for dual
power input applications, such as PCIE interfaced graphic
cards.
This control IC‘s protection features include a set of
sophisticated over-temperature, over-voltage, undervoltage, and over-current protections. Over-voltage results in the converter turning the lower MOSFETs on to
clamp the rising output voltage and protects the
microprocessor. The over-current protection level is set
through external resistors. The device also provides a
power-on-reset function and a programmable soft-start
to prevent wrong operation and limit the input surge
current during power-on or start-up.
The APW7098 is available in a QFN4x4-24A package.
Voltage-Mode Operation with Current Sharing
- Adjustable Feedback Compensation
- Regulated 1.5V on REFOUT/POK
Adjustable Over-Current Protection (OCP)
Accurate Load Line (DROOP) Programming
Adjustable Soft-Start
Over-Voltage Protection (OVP)
Under-Voltage Protection (UVP)
Over-Temperature Protection (OTP)
QFN4x4 24-Lead Package (QFN4x4-24A)
Lead Free and Green Devices Available
(RoHS Compliant)
Simplified Application Circuit
VIN1
VOUT
REFIN/EN
REFOUT/POK
APW7098
Applications
VIN2
COMP
FB
•
•
Graphics Card GPU Core Power Supply
Motherboard Chipset or DDR SDRAM Core Power
•
Supply
On-board High Power PWM Converter with Output Current up to 60A
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and
advise customers to obtain the latest version of relevant information to verify before placing orders.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
1
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APW7098
Ordering and Marking Information
Package Code
QA : QFN4x4-24A
Operating Ambient Temperature Range
E : -20 to 70 oC
Handling Code
TR : Tape & Reel
Assembly Material
G : Halogen and Lead Free Device
APW7098
Assembly Material
Handling Code
Temperature Range
Package Code
APW7098 QA :
XXXXX - Date Code
APW7098
XXXXX
Note: ANPEC lead-free products contain molding compounds/die attach materials and 100% matte tin plate termination finish; which
are fully compliant with RoHS. ANPEC lead-free products meet or exceed the lead-free requirements of IPC/JEDEC J-STD-020D for
MSL classification at lead-free peak reflow temperature. ANPEC defines “Green” to mean lead-free (RoHS compliant) and halogen
free (Br or Cl does not exceed 900ppm by weight in homogeneous material and total of Br and Cl does not exceed 1500ppm by
weight).
LGATE2
PHASE2
VCC
VCCDRV
PHASE1
LGATE1
Pin Configuration
24 23 22 21 20 19
18 UGATE2
UGATE1 1
BOOT1 2
17 BOOT2
5VCC 3
16 REFOUT/POK
25
PGND
AGND 4
15 REFIN/EN
RT
9 10 11 12
COMP
8
DROOP
7
CSP2
13 FB
CSN1
14 SS
CSP1 6
CSN2
MODE 5
QFN4x4-24A
(Top View)
Absolute Maximum Ratings
Symbol
VCC
VBOOT1/2
(Note 1)
Parameter
Rating
Unit
VCC Supply Voltage (VCC to AGND)
-0.3 ~ 15
V
BOOT1/2 Voltage (BOOT1/2 to PHASE1/2)
-0.3 ~ 15
V
<200ns pulse width
>200ns pulse width
-5 ~ VBOOT1/2+5
-0.3 ~ VBOOT1/2+0.3
V
<200ns pulse width
>200ns pulse width
-5 ~ VCC+5
-0.3 ~ VCC+0.3
V
<200ns pulse width
>200ns pulse width
-10 ~ 30
-2 ~ 15
V
UGATE1/2 Voltage (UGATE1/2 to PHASE1/2)
LGATE1/2 Voltage (LGATE1/2 to PGND)
PHASE1/2 Voltage (PHASE1/2 to PGND)
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
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APW7098
Absolute Maximum Ratings (Cont.)
Symbol
(Note 1)
Parameter
Rating
Unit
-0.3 ~ 42
-0.3 ~ 30
V
VCCDRV to AGND Voltage
-0.3 ~ 15
V
5VCC Supply Voltage (5VCC to AGND, V5VCC < VCC +0.3V)
-0.3 ~ 7
V
REFIN/EN, MODE to AGND Voltage
-0.3 ~ 7
V
-0.3 ~ V5VCC +0.3
V
BOOT1/2 to AGND Voltage
<200ns pulse width
>200ns pulse width
V5VCC
Input Voltage (REFOUT/POK, SS, FB, COMP, DROOP, RT, CSP1/2,
CSN1/2 to AGND)
PGND to AGND Voltage
PDMAX
Maximum Power Dissipation
Maximum Junction Temperature
TSTG
Storage Temperature Range
TSDR
Maximum Soldering Temperature, 10 Seconds
-0.3 ~ +0.3
V
Limited Internally
W
150
o
-65 ~ 150
o
260
o
C
C
C
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Thermal Characteristics
Symbol
θJA
θJC
Parameter
Junction-to-Ambient Resistance
Typical Value
QFN4x4-24A
Junction-to-Case Resistance
Unit
(Note 2)
45
°C/W
(Note 3)
QFN4x4-24A
7
Note 2 : θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. The exposed
pad of QFN4x4-24A is soldered directly on the PCB.
Note 3: The case temperature is measured at the center of the exposed pad on the underside of the QFN4x4-24A package.
Recommended Operating Conditions (Note 4)
Symbol
VCC
Parameter
Range
Unit
VCC Supply Voltage
8 ~ 13.2
V
V5VCC
5VCC Supply Voltage (V5VCC < VCC +0.3V)
5 ± 5%
V
VOUT
Converter Output Voltage
0.6 ~ 2.5
V
VIN1
PWM 1 Converter Input Voltage
3.1 ~ 13.2
V
VIN2
PWM 2 Converter Input Voltage
3.1 ~ 13.2
V
IOUT
Converter Output Current
~ 60
A
VREFIN/EN
REFIN/EN Input Voltage
0~2
V
-20 ~ 70
o
Junction Temperature
-20 ~ 125
o
CVCC
Linear Regulator Output Capacitor
0.8 ~ 15
µF
C5VCC
5VCC Linear Regulator Output Capacitor
0.8 ~ 15
µF
TA
TJ
Ambient Temperature
C
C
Note 4 : Refer to the typical application circuits.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
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APW7098
Electrical Characteristics
Refer to the typical application circuits. These specifications apply over VIN=12V, VOUT=1.2V and TA= -20 ~ 70°C, unless otherwise
specified. Typical values are at TA=25°C. The V5VCC is supplied by the internal regulator.
Symbol
Parameter
APW7098
Test Conditions
Unit
Min.
Typ.
Max.
SUPPLY CURRENT
ICC
VCC Nominal Supply Current
UGATEx and LGATEx Open,
FB forced above regulation point
-
5
10
mA
ISD
VCC Shutdown Supply Current
SS/EN=GND
-
5
-
mA
5VCC Rising Threshold Voltage
4.2
4.5
4.8
V
5VCC POR Hysteresis
0.4
0.58
0.76
V
POWER-ON-RESET (POR) AND OPERATION PHASE SELECTION
V5VCC_THR
MODE Rising Threshold Voltage
IMODE
VMODE Rising
MODE Pin Input Current
0.77
0.8
0.83
V
-100
-
+100
nA
VCC LINEAR CONTROLLER
VRRG_VCC
Regulated Voltage on VCC
IO=0A, RPULL-UP=1kΩ
8
8.5
9
V
Maximum VCCDRV Sink Current
VCC = VREG_VCC +200mV, VVCCDRV = 8V
5
-
-
mA
5VCC LINEAR REGULATOR
VREG_5VCC
Output Voltage
IO = 0A, VCC =8V
4.75
5
5.25
V
Line Regulation
IO = 0A, VCC = 8V ~ 13.2V
-20
-
20
mV
Load Regulation
IO = 3mA, VCC > 8V
-200
-
200
mV
Current-Limit
5VCC = GND
20
30
-
mA
-
0.6
-
V
REFERENCE VOLTAGE
VREF
Regulated Voltage on FB pin
Internal reference voltage used
o
Accuracy
TA=25 C
Over temperature
IFB
VREFIN/EN_THR
FB Pin Input Current
REFIN/EN Voltage Offset
VFB - VREFIN/EN, VREFIN/EN =0.6V~1.5V
Device Enable Voltage Threshold
On REFIN/EN pin, VREFIN/EN rising
VPOK
-
+1
-
+1.5
-100
-
+100
nA
%
-5
-
5
mV
0.37
0.4
0.43
V
-
50
-
mV
2.1
2.5
3.0
V
-
20
-
µs
-100
-
+100
nA
-
1.5
-
V
IO = 0~3mA, TA=25 C
-2
-
+2
IO = 0~3mA, Over temperature
-3
-
+3
REFOUT/POK Current-Limit
REFOUT/POK = GND
4
8
15
mA
REFOUT/POK Pull-Low
Resistance
IREFOUT/POK = 5mA
-
70
100
Ω
Device Enable Voltage
Hysteresis
IREFIN/EN
-1
-1.5
Internal/External Reference
Selection Voltage Threshold
On REFIN/EN pin
Reference Selection Debounce
Time
VREFIN/EN falling,
Switching to external reference
REFIN/EN Pin Input Current
REFOUT/POK Output Voltage
o
REFOUT/POK Accuracy
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
4
%
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APW7098
Electrical Characteristics (Cont.)
Refer to the typical application circuits. These specifications apply over VIN=12V, VOUT=1.2V and TA= -20 ~ 70°C, unless otherwise
specified. Typical values are at TA=25°C. The V5VCC is supplied by the internal regulator.
Symbol
Parameter
APW7098
Test Conditions
Unit
Min.
Typ.
Max.
ERROR AMPLIFIER
DC Gain
RL = 10kΩ to the ground
-
85
-
dB
Gain-Bandwidth Product
CL = 100pF, RL = 10kΩ to the ground
-
20
-
MHz
Slew Rate
CL = 100pF, IO = ±400µA
-
8
-
V/µs
Upper Clamp Voltage
IO = 1mA
2.7
3.0
-
V
Lower Clamp Voltage
IO = -1mA
-
-
0.1
V
COMP Pull-Low Resistance
In fault or shutdown condition
-
2
-
kΩ
RT = GND
135
150
165
RT = Floating
270
300
330
RT = 5VCC
360
400
440
-
1.5
-
V
-100
-
+100
µA
OSCILLATOR
FOSC
∆VOSC1/2
IRT
Oscillator Frequency
Oscillator Sawtooth Amplitude
kHz
RT Input Current
RT = GND/5VCC(5V)
RT 5VCC Level
For FOSC =150kHz
V5VCC-0.5
-
-
V
RT Floating Voltage
For FOSC =300kHz
1.2
3.6
V5VCC-1.2
V
RT GND Level
For FOSC =400kHz
-
-
0.3
V
85
88
-
%
2.6
-
A
Maximum Duty Cycle
MOSFET GATE DRIVERS
TD
UGATE1/2 Source Current
VBOOT = 12V, VUGATE-VPHASE = 2V
-
UGATE1/2 Sink Current
VBOOT = 12V, VUGATE-VPHASE = 2V
-
1
-
A
LGATE1/2 Source Current
VCC = 12V, VLGATE = 2V
-
2.6
-
A
LGATE1/2 Sink Current
VCC =12V, VLGATE = 2V
-
1.4
-
A
UGATE1/2 Source Resistance
VBOOT = 12V, 100mA Source Current
-
2.5
3.75
Ω
UGATE1/2 Sink Resistance
VBOOT = 12V, 100mA Sink Current
-
2
3
Ω
LGATE1/2 Source Resistance
VCC = 12V, 100mA Source Current
-
2
3
Ω
LGATE1/2 Sink Resistance
VCC = 12V, 100mA Sink Current
-
1.4
2.1
Ω
-
30
-
ns
-100
-
+100
nA
Sourcing current
80
-
-
Sinking current
15
-
-
-
3
-
Dead-Time
CURRENT SENSE AND DROOP FUNCTION
ICSP
CSP1/2 Pin Input Current
ICSN
CSN1/2 Maximum Output Current
R CSN1/2 = 2kΩ,
Current Sense Amplifier Bandwidth
µA
MHz
DROOP Output Current Accuracy
RDROOP = 2kΩ, VDROOP =0.005V
-
50
-
µA
DROOP Accuracy
∆VFB = VDROOP/20, VDROOP = 1V
-5
-
+5
mV
-10
-
+10
%
Current Difference Between
Channel1/2 and Average Current
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
5
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APW7098
Electrical Characteristics (Cont.)
Refer to the typical application circuits. These specifications apply over VIN=12V, VOUT=1.2V and TA= -20 ~ 70°C, unless otherwise
specified. Typical values are at TA=25°C. The V5VCC is supplied by the internal regulator.
Symbol
Parameter
APW7098
Test Conditions
Min.
Unit
Typ.
Max.
SOFT-START AND ENABLE
ISS
8
10
12
µA
Soft-Start Complete Threshold
-
3.2
-
V
SS Pull-low Resistance
-
10
18
kΩ
Soft-Start Current Source
Flowing out of SS pin
POWER-OK AND PROTECTIONS
VUV
Over-Current Trip Level
ICS1 + ICS2
110
120
140
µA
FB Under-Voltage Threshold
~ 2µs noise filter, VFB falling,
Percentage of VR at Error Amplifier
40
50
60
%
-
87.5
-
%
115
125
135
%
-
60
80
mV
-
150
-
o
-
o
VPOK_L
POK Lower Threshold
VOV,
VPOK_H
FB Over-Voltage Threshold
and POK Upper Threshold
~ 2µs noise filter, VFB rising
Percentage of VR at Error Amplifier
FB Over-Voltage Hysteresis
TOTR
Over-Temperature Trip Level
TJ rising
Over-Temperature Hysteresis
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
-
6
50
C
C
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APW7098
Typical Operating Characteristics
5VCC Line Regulation
5VCC Load Regulation
6
VCC=12V, VIN=12V
5VCC Voltage,V5VCC (V)
5VCC Voltage,V5VCC (V)
6
5
4
3
2
5
4
3
2
1
1
0
0
0
2
4
6
8
10
12
0
14
5
10
Output Voltage Load Regulation
25
30
35
40
0.606
VCC=12V
VCC=12V, VIN=12V
Feedback Voltage,VFB (V)
Feedback Voltage,VFB (V)
20
Output Voltage Line Regulation
0.606
0.604
0.602
0.6
0.598
0.604
0.602
0.6
0.598
0.596
0.596
0.594
0.594
0
10
20
30
40
5
50
6
7
Reference Voltage Accuracy Over
Switching Frequency, FSW (kHz)
0.605
0.603
0.601
0.599
0.597
0.595
0.593
20
40
60
80
100 120
o
12
13
310
300
290
280
-20
0
20
40
60
80
100
120
o
Junction Temperature, TJ ( C)
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
11
320
270
-40
0.591
0
10
330
0.607
-20
9
Switching Frequency Over Temperature
Temperature
0.609
-40
8
VIN Voltage,VIN (V)
Output Current,IOUT (A)
Reference Voltage,VREF (V)
15
5VCC Load Current ,I5VCC (mA)
VCC Voltage,VCC (V)
Junction Temperature, TJ ( C)
7
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APW7098
Operating Waveforms
Power On
Power Off
IOUT=10A
IOUT=10A
V5VCC
V5VCC
1
1
VCOMP
VCOMP
2
2
VSS
VSS
3
3
VOUT
4
VOUT
4
CH1: V5VCC (5V/div)
CH2: VCOMP (1V/div)
CH3: VSS (5V/div)
CH4: VOUT (1V/div)
Time: 5ms/div
CH1: V5VCC (5V/div)
CH2: VCOMP (1V/div)
CH3: VSS (5V/div)
CH4: VOUT (1V/div)
Time: 5ms/div
Shutdown by REFIN/EN Pin
Enable by REFIN/EN Pin
IOUT=10A
IOUT=10A
VREFIN/EN
VREFIN/EN
1
1
VCOMP
VCOMP
2
2
VSS
VSS
3
3
4
VOUT
VOUT
4
CH1: VREFIN/EN (5V/div)
CH2: VCOMP (1V/div)
CH3: VSS (2V/div)
CH4: VOUT (1V/div)
Time: 5ms/div
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
CH1: VREFIN/EN (5V/div)
CH2: VCOMP (1V/div)
CH3: VSS (2V/div)
CH4: VOUT (1V/div)
Time: 5ms/div
8
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APW7098
Operating Waveforms (Cont.)
External Step-Up Reference by VREFIN/EN
External Step-Down Reference by VREFIN/EN
VREFIN/EN
VREFIN/EN
1
1
VFB
VFB
VSS
VSS
2
2
IOUT
3
IOUT
3
4
4
CH1: VREFIN/EN (1V/div)
CH2: VFB (500mV/div)
CH3: VSS (1V/div)
CH4: IOUT (10A/div)
Time: 200µs/div
CH1: VREFIN/EN (1V/div)
CH2: VFB (500mV/div)
CH3: VSS (1V/div)
CH4: IOUT (10A/div)
Time: 200µs/div
Power On Without VIN2 Voltage
Under-Voltage Protection (UVP)
VOUT
VFB
1
1
VPHASE1
VPHASE1
2
2
VPHASE2
VPHASE2
3
3
4
Vss
Vss
4
CH1: VOUT (1V/div)
CH2: VPHASE1 (10V/div)
CH3: VPHASE2 (2V/div)
CH4: VSS (2V/div)
Time: 5ms/div
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
CH1: VFB (500mV/div)
CH2: VPHASE1 (10V/div)
CH3: VPHASE2 (10V/div)
CH4: VSS (2V/div)
Time: 200µs/div
9
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APW7098
Operating Waveforms (Cont.)
Load Transient , 0A==>40A
1
2
Load Transient , 40A==>0A
VPHASE1
VPHASE1
1
IPHASE2
IPHASE2
2
VOUT
VOUT
3
3
IOUT
RSEN=3kΩ
L=0.56µH
DCR=4mΩ
RSEN=3kΩ
L=0.56µH
DCR=4mΩ
IOUT
4
4
CH1: VPHASE1 (20V/div)
CH2: IPHASE2 (20A/div)
CH3: VOUT (AC, 200mV/div)
CH4: IOUT (10A/div)
Time: 20µs/div
CH1: VPHASE1 (20V/div)
CH2: IPHASE2(20A/div)
CH3: VOUT (AC, 200mV/div)
CH4: IOUT (10A/div)
Time: 20µs/div
OCP at Slow Slew IOUT
RSEN=1.5kΩ
L=0.56µH
DCR=4mΩ
Short-Circuit Test After Power On
RSEN=1.5kΩ
L=0.56µH
DCR=4mΩ
IL1
1
IL1
1
IL2
IL2
2
2
VSS
3
VOUT
4
VOUT
4
CH1: IL1 (10A/div)
CH2: IL2 (10A/div)
CH3: VSS (5V/div)
CH4: VOUT (1V/div)
Time: 5ms/div
CH1: IL1 (10A/div)
CH2: IL2 (10A/div)
CH3: VSS (5V/div)
CH4: VOUT (1V/div)
Time: 5ms/div
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
VSS
3
10
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APW7098
Operating Waveforms (Cont.)
Short-Circuit Test Before Power On
OVP After Power On
RSEN=1.5kΩ
L=0.56µH
DCR=4mΩ
Pull-Up VFB > V OV
VSS
1
IL1
VFB
1
VLG1
2
IL2
3
2
VLG2
VSS
3
4
VOUT
4
CH1: VFB (1V/div)
CH2: VSS (2V/div)
CH3: VLG1 (10V/div)
CH4: VLG2 (10V/div)
Time: 100µs/div
CH1: IL1 (10A/div)
CH2: IL2 (10A/div)
CH3: VSS (5V/div)
CH4: VOUT (1V/div)
Time: 5ms/div
Pin Description
PIN
FUNCTION
NO.
NAME
1
UGATE1
High-side Gate Driver Output for channel 1. Connect this pin to the gate of high-side MOSFET.
This pin is monitored by the adaptive shoot-through protection circuitry to determine when the
high-side MOSFET has turned off.
2
BOOT1
Bootstrap Supply for the floating high-side gate driver of channel 1. Connect the Bootstrap
capacitor between the BOOT1 pin and the PHASE1 pin to form a bootstrap circuit. The bootstrap
capacitor provides the charge to turn on the high-side MOSFET. Typical values for CBOOT ranged
from 0.1µF to 1µF. Ensure that CBOOT is placed near the IC.
3
5VCC
Internal Regulator Output. This is the output pin of the linear regulator, which is converting power
from VCC and provides output current up to 20mA minimums for internal bias and external usage.
4
AGND
Signal Ground for the IC. All voltage levels are measured with respect to this pin. Tie this pin to the
ground island/plane through the lowest impedance connection available.
5
MODE
Operation Phase Selection Input. Pulling this pin lower than 0.64V sets two-phase operation with
both channels enabled. Pulling this pin higher than 0.8V sets single-phase operation with the
channel 2 disabled. Once operating in single-phase mode, the operation mode is latched. It is
required to toggle SS, REFIN/EN, or 5VCC pin to reset the IC.
6
CSP1
Positive Input of current sensing Amplifier for channel 1. This pin combined with CSN1 senses the
inductor current through an RC network.
7
CSN1
Negative Input of current sensing amplifier for channel 1. This pin combined with CSP1 senses
the inductor current through an RC network.
8
CSN2
Negative Input of current sensing amplifier for channel 2. This pin combined with CSP2 senses
the inductor current through an RC network.
9
CSP2
Positive Input of current sensing Amplifier for Channel 2. This pin combined with CSN2 senses the
inductor current through an RC network.
Copyright  ANPEC Electronics Corp.
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APW7098
Pin Description (Cont.)
PIN
NO.
10
FUNCTION
NAME
DROOP
Load Line (droop) Setting. Connect a resistor between this pin and AGND to set the droop. A
sourcing current, proportional to output current is present on the DROOP pin. The droop scale
factor is set by the resistors (connected with CSP1, CSP2, and DROOP), resistance of the output
inductors, and the internal voltage divider with the ratio of 5%.
Operating Frequency Setting. The three-level input pin sets the operating frequency for each
channel.
RT
Operating Frequency (kHz)
GND
150
Floating
300
5VCC
400
Error Amplifier Output. Connect the compensation network between COMP, FB, and VOUT for Type
2 or Type 3 feedback compensation.
11
RT
12
COMP
13
FB
Feedback Voltage. This pin is the inverting input to the error comparator. A resistor divider from
the output to the AGND is used to set the regulation voltage.
14
SS
Soft-start Current Output. Connect a capacitor from this pin to the AGND to set the soft-start
interval. Pulling the voltage on this pin below 0.5V causes COMP to pull low and then shuts off the
output.
15
REFIN/EN
External Reference and Enable Input. The IC uses the voltage (VREFIN/EN) as reference voltage of
the converter with soft-start control. If this pin is driven by an external voltage ranged from 0.4V to
2V. The IC is disabled if the voltage is below 0.4V (typical). If external reference is not available,
then connect this pin to 5VCC for internal 0.6V reference.
16
REFOUT/PO
K
Power-OK and 1.5V Reference Output. This pin is a reference output used to indicate the status
of the voltages on SS pin and FB pin. REFOUT/POK provides 1.5V reference if VFB> 87.5% of
reference (VR).
17
BOOT2
Bootstrap Supply for the floating high-side gate driver of channel 2. Connect the Bootstrap
capacitor between the BOOT2 pin and the PHASE2 pin to form a bootstrap circuit. The bootstrap
capacitor provides the charge to turn on the high-side MOSFET. Typical values for CBOOT range
from 0.1µF to 1µF. Ensure that CBOOT is placed near the IC.
18
UGATE2
High-side Gate Driver Output for Channel 2. Connect this pin to the gate of high-side MOSFET.
This pin is monitored by the adaptive shoot-through protection circuitry to determine when the
high-side MOSFET has turned off.
19
PHASE2
Switch Node for Channel 2. Connect this pin to the source of high-side MOSFET and the drain of
the low-side MOSFET. This pin is used as sink for UGATE2 driver. This pin is also monitored by
the adaptive shoot-through protection circuitry to determine when the high-side MOSFET has
turned off. An Schottky diode between this pin and the ground is recommended to reduce
negative transient voltage that is common in a power supply system.
20
LGATE2
Low-side Gate Driver Output for Channel 2. Connect this pin to the gate of low-side MOSFET.
This pin is monitored by the adaptive shoot-through protection circuitry to determine when the
low-side MOSFET has turned off.
21
VCCDRV
Drive for External Linear Regulator. This pin is the drive output for the external linear regulator.
Connect this pin to base/gate of NPN/NMOS transistor as the pass element.
22
VCC
Supply Voltage. This pin along with VCCDRV pin and external pass element provides 8.5V
regulated bias supply, low-side gate drivers, and the bootstrap circuit for high-side drivers. This pin
can receive a well-decoupled 8V~13.2V supply voltage alone if the VCCDRV is left open. Ensure
that this pin is bypassed by a ceramic capacitor next to the pin.
23
LGATE1
Low-side Gate Driver Output for Channel 1. Connect this pin to the gate of low-side MOSFET.
This pin is monitored by the adaptive shoot-through protection circuitry to determine when the
low-side MOSFET has turned off.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
12
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APW7098
Pin Description (Cont.)
PIN
NO.
FUNCTION
NAME
24
PHASE1
Switch Node for Channel 1. Connect this pin to the source of high-side MOSFET and the drain of
the low-side MOSFET. This pin is used as sink for UGATT1 driver. This pin is also monitored by
the adaptive shoot-through protection circuitry to determine when the high-side MOSFET has
turned off. An Schottky diode between this pin and the ground is recommended to reduce
negative transient voltage, which is common in a power supply system.
25
PGND
Power Ground for the low-side gate drivers. Connect this pin to the source of low-side MOSFETs.
This pin is used as sink for LGATE1 and LGATE2 drivers.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
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APW7098
Block Diagram
REFOUT/POK
VCCDRV
VCC
VCC
Linear
Controller 8.5V
1.5V
Reference
VCC
5VCC
Linear
Regulator
5VCC
87.5%
125%
OV
Power-onReset
UV
V5VCC
50%
Over-Temperature
Protection
FB
Droop
Control
0.6V
VREF
PGND
SSEND
DROOP
'' L''
Control
Logic
Operation
Phase
Selection
+
''H''
REFIN/EN
3.6V
VR
ISS
10µA
Error
Amplifier
V5VCC-1V
MODE
SS
Soft-Start
0.4V
Selectable
Oscillator
and
Sawtooth
RT
VCC
COMP
VOSC1
AGND
VOSC2
VCC
150/300/400 kHz
BOOT2
BOOT1
PWM Signal Controller
UGATE2
PHASE2
UGATE1
VCC
VCC
LGATE2
PHASE1
LGATE1
120µA
OC
ICS1+ICS2
CSN2
CSP2
Current
Sense
ICS2
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
Current
Balance
ICS1
ICS1+ICS2
14
Current
Sense
CSN1
CSP1
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APW7098
Typical Application Circuits
1. APW7098 PWM Converter With 8V Gate Drive
5
R10
1.2kΩ
VIN
+12V
R12
1kΩ
C16
1µF
BOOT1
UGATE1
Q5
2N7002
21
22
C13
1µF
3
C14
1µF
15
14
C15
0.1µF
11
10
R11
2kΩ
16
VCCDRV
PHASE1
LGATE1
5VCC
PGND
R1
1.5kΩ
R3
51Ω
Q2
23
SS
C6
1200µFx3
25
VOUT
1.2V
C7
47µFx2
IOCP=45A
REFIN/EN
Q1 : APM4350KPx1
Q2 : APM4354KPx2
APW7098
RT
UGATE2 18
DROOP
PHASE2
19
C8
10µF
C9
330µFx3
Q3
L2
0.56µH
C10
0.1µF
DCR=4mΩ
REFOUT/POK
CSP1
13
R2
1.5kΩ
24
L1
0.56µH
DCR=4mΩ
LGATE2
12
Q1
C5
0.1µF
VCC
C3
2.2nF
C2
22nF
C4
10µF
1
BOOT2 17
FOSC=300kHz
R4
2kΩ
2
MODE
CSN1
COMP
CSP2
FB
CSN2
Q4
20
R5
1.5kΩ
6
PHASE1
7
9
PHASE2
8
AGND
4
C1
10nF
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
R8
1.5kΩ
15
C12
0.1µF
(X7R)
R6
1.5kΩ
R7
1.5kΩ
C11
0.1µF
(X7R)
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APW7098
Typical Application Circuits (Cont.)
2. APW7098 PWM Converter With 12V Gate Drive
VIN
+12V
5
BOOT1
UGATE1
21
VCCDRV
22
VCC
C13
1µF
3
C14
1µF
15
14
C15
0.1µF
PHASE1
FOSC=300kHz
10
R11
2kΩ
16
LGATE1
5VCC
C2
22nF
PGND
SS
R2
1.5kΩ
R1
1.5kΩ
R3
51Ω
Q2
23
C6
1200uFx3
25
VOUT
1.2V
C7
47µFx2
IOCP=45A
APW7098
RT
17
UGATE2 18
DROOP
PHASE2
REFOUT/POK
CSP1
13
24
L1
0.56µH
C5
0.1µF
Q1 : APM4350KPx1
Q2 : APM4354KPx2
LGATE2
12
Q1
1
REFIN/EN
C3
2.2nF
R4
2kΩ
C4
10µF
DCR=4mΩ
BOOT2
11
2
MODE
CSN1
COMP
CSP2
FB
CSN2
19
C8
10µF
Q3
4
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
L2
0.56µH
C10
0.1µF
DCR=4mΩ
Q4
20
R5
1.5kΩ
6
PHASE1
7
9
PHASE2
8
AGND
C1
10nF
C9
330µFx3
R8
1.5kΩ
16
C12
0.1µF
(X7R)
R6
1.5kΩ
R7
1.5kΩ
C11
0.1µF
(X7R)
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APW7098
Function Description
Voltage(V)
VCC Linear Controller
VCC
The VCC linear-regulator controller is an analog gain
block with an open-drain n-channel output. It drives an
VSS
external NPN or N-channel MOSFET pass transistor with
a 1kΩ (typical) pull-up resistor and senses the feedback
voltage via VCC pin. The regulator uses a 1µF (minimum)
ceramic output capacitor and is designed to deliver
V5VCC
5VCC
POR
VPOK
100mA (at 8.5V) for VCC.
1.5V
VFB
0.6V
VSS_VT
5VCC Linear Regulator
5VCC is the output terminal of the internal 5V linear
regulator which regulates a 5V voltage on 5VCC by
Time
Figure 1. Power Sequence
controlling an internal bypass transistor between VCC
and 5VCC. The linear regulator powers the internal
When soft-start is initiated, the internal 10µA current
source starts to charge the capacitor. When the soft-start
control circuitry and is stable with a low-ESR ceramic
output capacitor. Bypass 5VCC to GND with a ceramic
voltage across the soft-start capacitor reaches the enabled threshold about 0.8V (VSS_VT), the internal reference
capacitor of at least 1µF. Place the capacitor physically
close to the IC to provide good noise decoupling. The
starts to rise and follows the soft-start voltage with converter operating at 150k/300k/400kHz PWM switching
linear regulator can also provide output current up to
20mA for external loads. The linear regulator with current-
frequency. When output voltage rises to 87.5% of the
regulation voltage, the power-ok is enabled. The soft-
limit protection can protect itself during over-load or shortcircuit conditions on 5VCC pin.
The 5VCC linear regulator stops regulating in Over-Tem-
start time (from the moment of enabling the IC to the
moment when VPOK goes high) can be expressed as the
following equation:
perature Protection. When the junction temperature is
cooled by 50oC, the 5VCC linear regulator starts to regu-
TSS =
late the output voltage again.
CSS × (VSS_VT + VREF × 0.875)
ISS
where
CSS= external soft-start capacitor
5VCC Power-On-Reset (POR) and REFIN/EN (External
VSS_VT= internal soft-start threshold voltage, is about
0.8V
Reference and Enable Input)
Figure 1 shows the power sequence. The APW7098
VREF= 0.6V or the voltage on the REFIN/EN pin
keeps monitoring the voltage on 5VCC pin to prevent
ISS= soft-start current=10µA
wrong logic operations which may occur when 5VCC
voltage is not high enough for the internal control cir-
During soft-start stage, the under-voltage protection is
cuitry to operate. The 5VCC POR has a rising threshold of 4.6V (typical) with 0.58V of hysteresis. After the
inhibited; however, the over-voltage and over-current protection functions are enabled. If the output capacitor has
5VCC voltage exceeds its rising Power-On-Reset
(POR) voltage threshold, the IC starts a start-up pro-
residue voltage before start-up, both lower and upper
MOSFETs are in off-state until the internal soft-start volt-
cess and then ramps up the output voltage to the setting
of output voltage. The 5VCC POR signal resets the
age equals to the FB pin voltage. This will ensure the
output voltage starts from its existing voltage level.
fault latch, set by the under-voltage or over-current event,
when the signal is at a low level.
Reference Voltage Selection and Shutdown Control
The APW7098 features a reference selection function
to use either internal 0.6V or external reference voltage.
During the beginning of soft-start, the voltage on
Copyright  ANPEC Electronics Corp.
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APW7098
Function Description (Cont.)
Reference Voltage Selection and Shutdown Control
(Cont.)
PCIE
+12V
VCC
PWM 1
converter
REFIN/EN pin determines which reference voltage is
used. If this REFIN/EN pin is driven by an external
voltage ranged from 0.4V to 2V, the IC uses the VREFIN/EN
External
Power
voltage as reference voltage of the converter with softstart control. If external reference is not available, con-
Operation
Phase
Selection
MODE
VIN2
PWM 2
converter
PHASE2
nect this pin to 5VCC for internal 0.6V reference used.
Once the internal or external reference is selected, the
4V
reference source is latched. Cycling the POR signal resets the latch.
VIN2 sensing
circuit
Figure 2. VIN2 Sensing Circuit
The other function of REFIN/EN pin is used to enable or
shut off the IC. Pulling the VREFIN/EN voltage below 0.4V
Over-Voltage Protection (OVP)
The over-voltage protection function monitors the output
(typical) shuts down the two-phase PWM controller. In
the shutdown mode, the two-phase UGATE and LGATE
voltage through the FB pin. When the FB voltage increases over 125% of the reference voltage (VR) due to
signals are pulled to PHASE and PGND respectively, the
the high-side MOSFET failure or other reasons, the overvoltage protection comparator designed with a 2µs
output is floating.
noise filter will force the low-side MOSFET gate drivers
high. This action actively pulls down the output voltage
Operation Phase Selection
The MODE pin programs single- or two- phase operation.
It has a typical value for rising threshold of 0.8V, VMODE_THR,
and eventually attempts to trigger the over-current shutdown of an ATX power supply. As soon as the output
with 0.16V of hysteresis (0.64V), VMODE_THF. When the MODE
voltage is within regulation, the OVP comparator is
disengaged. The chip will restore its normal operation.
pin voltage is higher than VMODE_THR, the device operates
in single-phase; when the MODE pin voltage is lower
When the OVP occurs, the REFOUT/POK will drop to low
as well.
This OVP scheme only clamps the voltage overshoot,
than VMODE_THF and VIN2 supply voltage is above approximate 4V, the device operates in two-phase operation.
This function makes the APW7098 ideally suitable for
dual power input applications like PCIE interfaced graphic
and does not invert the output voltage when otherwise
activated with a continuously high output from low-side
cards.
The figure 2 shows the power sources of the two
channels. The input power of PWM1 converter is supplied by PCIE bus power and the input power of PWM2
MOSFETs driver, which is a common problem for OVP
schemes with a latch.
Under-Voltage Protection (UVP)
In the process of operation, when a short-circuit occurs,
converter is supplied by an external power. If the input
power connector of PWM2 converter is not plugged into
the output voltage will drop quickly. Before the over-current protection responds, the output voltage will fall
the socket before start-up, the internal VIN2 sensing circuit
can sense the absence of VIN2 and set the IC to operate in
out of the required regulation range. The under-voltage
continually monitors the VFB voltage after soft-start is
single-phase mode with PWM2 disabled. When the IC
operates in two-phase mode, it can switch the operating
completed. If a load step is strong enough to pull the
output voltage lower than the under-voltage threshold,
mode from two-phase to single-phase operation. Once
operating in single-phase mode, the operation mode is
the IC shuts down converter’s output. Cycling the 5VCC
POR or REFIN/EN signal resets the fault latch and starts
latched. It is required to toggle SS, REFIN/EN, or 5VCC
pin to reset the IC.
a start-up process. The under-voltage threshold is 50% of
the nominal output voltage. The under-voltage comparator has a built-in 2µs noise filter to prevent the chips
from wrong UVP shutdown being caused by noise.
Copyright  ANPEC Electronics Corp.
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APW7098
Function Description (Cont.)
Over-Current Protection (OCP)
Current Sharing
Figure 3 shows the circuit of sensing inductor current.
Connecting a series resistor (R S) and a capacitor (C S)
The APW7098 uses inductor’s DCRs and external networks to sense the both currents flowing through the inductors of the PWM1 and PWM2 channels. The current
network in parallel with the inductor and measuring
the voltage (VC) across the capacitor can sense the inductor current.
sharing circuit, with closed-loop control, uses the sensed
currents to adjust the two-phase inductor currents. For
VL
L
example, if the sensed current of PWM1 is bigger than
PWM2, the duty of PWM1 will decrease and the duty of
DCR
PHASE
IL
Rs
PWM2 will increase. Then, the device will reduce IL1
current and increase IL2 current for current sharing.
Cs
DROOP
VC
CSP
In some high current applications, a requirement on
CSN
precisely controlled output impedance is imposed. This
dependence of output voltage on load current is often
R2
termed droop regulation.
As shown in figure 4, the droop control block generates
Figure 3. Illustration of Inductor Current Sensing Circuit
The equations of the sensing network are:
a voltage through external resistor R DROOP and then
set the droop voltage. The droop voltage, VDROOP , is
VL (s)=IL (s) × (SL+DCR)
proportional to the total current in two channels. As
shown in the following equation:
1
IL(S) × (SL + DCR )
VC(S) = VL(S) ×
=
1 + SRSCS
1 + SRSCS
Take
VDROOP = 0.05 × [(ICS1 + ICS 2 ) × RDROOP ]
L
DCR
for example, if the above equation is true, the voltage
R SC S =
The VDROOP voltage is used the regulator to adjust the output voltage, therefore, it is equal to the reference voltage
minus the droop voltage.
across the capacitor CS is equal to voltage drop across
the inductor DCR, and the voltage VC is proportional to
the current IL. The sensing current through the resistor
R2 can be expressed as the following equation:
ICS =
Droop Control
IL × DCR
R2
VDROOP
RDROOP
where
ICS is the sensed current
VR
VREFIN/EN or 0.6V
IL is the inductor current
DCR is the inductor resistance
R2 is the sense resistor
Figure 4. Illustration of Droop Setting Function
The APW7098 is a two-phase PWM controller; therefore,
the IC has two sensed current parts, ICS1 and ICS2. When
ICS1 plus ICS2 is greater than 120µA, the over current occurs.
In over-current protection, the IC shuts off the converter
and then initials a new soft-start process. After 3 overcurrent events are counted, the device turns off both highside and low-side MOSFETs and the converter’s output
is latched to be floating.
Copyright  ANPEC Electronics Corp.
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APW7098
Function Description (Cont.)
Over-Temperature Protection (OTP)
When the junction temperature increases above the rising threshold temperature TOTR, the IC will enter the overtemperature protection state that suspends the PWM,
which forces the LGATE and UGATE gate drivers to output low voltages and turns off the 5VCC linear regulator
output. The thermal sensor allows the converters to start
a start-up process and regulate the output voltage again
after the junction temperature cools by 50oC. The OTP is
designed with a 50oC hysteresis to lower the average TJ
during continuous thermal overload conditions, which
increases lifetime of the APW7098.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
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APW7098
Application Information
Output Voltage Setting
FLC
The output voltage is adjustable from 0.6V to 2.5V
with a resistor-divider connected with FB, AGND, and
converter’s output. Using 1% or better resistors for the
-40dB/dec
GAIN (dB)
resistor-divider is recommended. The output voltage
is determined by:

R
VOUT = 0.6 ×  1 + TOP

R
GND




FESR
Where 0.6 is the reference voltage, RTOP is the resistor
connected from converter’s output to FB, and RGND is the
-20dB/dec
resistor connected from FB to the the AGND. Suggested
RGND is in the range from 1K to 20kΩ. To prevent stray
pickup, locate resistors R TOP and R GND close to the
APW7098.
Frequency(Hz)
Figure 6. Frequency Resopnse of the LC filters
PWM Compensation
The PWM modulator is shown in figure 7. The input is the
output of the error amplifier and the output is the PHASE
The output LC filter of a step down converter introduces a
double pole, which contributes with -40dB/decade gain
slope and 180 degrees phase shift in the control loop. A
node. The transfer function of the PWM modulator is given
by :
compensation network among COMP, FB, and V OUT
should be added. The compensation network is shown
GAINPWM =
in Figure 8. The output LC filters consists of the
output inductors and output capacitors. For two-phase
convertor, when assuming VIN1=VIN2=VIN, L1=L2=L, the
transfer function of the LC filter is given by:
GAINLC =
OSC
1 + s × ESR × COUT
Driver
Figure 7. The PWM Modulator
The compensation network is shown in figure 8. It provides a close loop transfer function with the highest zero
crossover frequency and sufficient phase margin.
The transfer function of error amplifier is given by :
the ESR of the output capacitors.
V OUT
GAINAMP
L2=L
COUT
1 
1 
// R2 +

VCOMP
sC1 
sC2 
=
=
1 
VOUT

R1//  R3 +

sC3



1
1

 
s +
 ×  s +

R2
×
C2
(
R1
+
R3
)
×
C3
R1 + R3

 

=
×
C1 + C2  
1
R1× R3 × C1 

s s +
× s +

R2 × C1× C2  
R3 × C3 

ESR
Figure 5. The Output LC Filter
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
PHASE
Output of Error
Amplifier
The FLC is the double-pole frequency of the two-phase LC
filters, and FESR is the frequency of the zero introduced by
V PHASE2
PWM
Comparator
∆VOSC
s2 ×
L1=L
VIN
Driver
1
L × COUT + s × ESR × COUT + 1
2
The poles and zero of this transfer functions are:
1
FLC =
1
2× π×
L × COUT
2
1
FESR =
2 × π × ESR × COUT
V PHASE1
VIN
∆VOSC
21
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APW7098
Application Information (Cont.)
PWM Compensation (Cont.)
4. Set the pole at the ESR zero frequency FESR:
The pole and zero frequencies of the transfer function
FP1 = FESR
Calculate the C1 by the following equation:
are:
FZ1 =
1
2 × π × R2 × C2
C1 =
1
FZ2 =
2 × π × (R1+ R3) × C3
1
FP1 =
 C1× C2 
2 × π × R2 × 

 C1 + C2 
1
FP2 =
×
π
×
2
R3 × C3
5. Set the second pole FP2 at the half of the switching
frequency and also set the second zero FZ2 at the output LC
filter double pole FLC. The compensation gain should not
exceed the error amplifier open loop gain, check the
compensation gain at FP2 with the capabilities of the
error amplifier.
C1
R3
C3
C2
2 × π × R2 × C2 × FESR − 1
R2
FP2 = 0.5 X FSW
C2
FZ2 = FLC
VOUT
R1
FB
Combine the two equations will get the following
component calculations:
VCOMP
VREF
R3 =
R1
FSW
−1
2 × FLC
C3 =
1
π × R3 × FSW
Figure 8. Compensation Network
The closed loop gain of the converter can be written as:
GAINLC X GAINPWM X GAINAMP
Figure 9. shows the asymptotic plot of the closed loop
converter gain, and the following guidelines will help to
FZ1
FZ2
FP1
FP2
design the compensation network. Using the below
guidelines should give a compensation similar to the
GAIN (dB)
curve plotted. A stable closed loop has a -20dB/ decade
slope and a phase margin greater than 45 degree.
Compensation Gain
20log
(R2/R1)
20log
(VIN/ΔVOSC)
1. Choose a value for R1, usually between 1K and 5K.
2. Select the desired zero crossover frequency
FO= (1/5 ~ 1/10) X FSW
FLC
Use the following equation to calculate R2:
FESR
∆VOSC FO
R2 =
×
× R1
VIN
FLC
PWM & Filter Gain
Frequency(Hz)
3. Place the first zero FZ1 before the output LC filter double
pole frequency FLC.
Figure 9. Converter Gain and Frequency
FZ1 = 0.75 X FLC
Calculate the C2 by the equation:
Output Inductor Selection
The duty cycle (D) of a buck converter is the function of
the input voltage and output voltage. Once an output volt-
1
C2 =
2 × π × R2 × FLC × 0.75
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
Converter Gain
age is fixed, it can be written as:
22
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APW7098
Application Information (Cont.)
Output Inductor Selection (Cont.)
caused by the AC peak-to-peak sum of the inductor’s
current. The ripple voltage of output capacitors can be
V
D = OUT
VIN
represented by:
For two-phase converter, the inductor value (L) determines
the sum of the two inductor ripple currents, ∆IP-P, and af-
∆VESR
fects the load transient reponse. Higher inductor value
These two components constitute a large portion of the
total output voltage ripple. In some applications, multiple
reduces the output capacitors’ripple current and induces
lower output ripple voltage. The ripple current can be
capacitors have to be paralleled to achieve the desired
ESR value. If the output of the converter has to support
approxminated by:
∆IP - P =
∆ IP − P
8 × COUT × FSW
= ∆IP − P × RESR
∆VCOUT =
VIN - 2VOUT VOUT
×
FSW × L
VIN
Where FSW is the switching frequency of the regulator.
Although the inductor value and frequency are increased
and the ripple current and voltage are reduced, a tradeoff
exists between the inductor’s ripple current and the regulator load transient response time.
A smaller inductor will give the regulator a faster load transient response at the expense of higher ripple current.
Increasing the switching frequency (FSW ) also reduces
the ripple current and voltage, but it will increase the
switching loss of the MOSFETs and the power dissipation of the converter. The maximum ripple current occurs at the maximum input voltage. A good starting point
is to choose the ripple current to be approximately 30%
of the maximum output current. Once the inductance value
has been chosen, select an inductor that is capable of
carrying the required peak current without going into
saturation. In some types of inductors, especially core
that is made of ferrite, the ripple current will increase
abruptly when it saturates. This results in a larger output ripple voltage.
another load with high pulsating current, more capacitors are needed in order to reduce the equivalent ESR
and suppress the voltage ripple to a tolerable level. A
small decoupling capacitor in parallel for bypassing
the noise is also recommended, and the voltage rating
of the output capacitors are also must be considered.
To support a load transient that is faster than the
switching frequency, more capacitors are needed for
reducing the voltage excursion during load step change.
For getting same load transient response, the output
capacitance of two-phase converter only needs around
half of output capacitance of single-phase converter.
Another aspect of the capacitor selection is that the
total AC current going through the capacitors has to be
less than the rated RMS current specified on the capacitors in order to prevent the capacitor from overheating.
Input Capacitor Selection
Use small ceramic capacitors for high frequency
decoupling and bulk capacitors to supply the surge cur-
Output Capacitor Selection
rent needed each time high-side MOSFET turns on. Place
the small ceramic capacitors physically close to the
Output voltage ripple and the transient voltage deviation are factors that have to be taken into con-
MOSFETs and between the drain of high-side MOSFET
and the source of low-side MOSFET.
sideration when selecting output capacitors. Higher
capacitor value and lower ESR reduce the output ripple
The important parameters for the bulk input capacitor are
the voltage rating and the RMS current rating. For reliable
and the load transient drop. Therefore, selecting high
performance low ESR capacitors is recommended for
operation, select the bulk capacitor with voltage and current ratings above the maximum input voltage and larg-
switching regulator applications. In addition to high frequency noise related to MOSFET turn-on and turn-off,
est RMS current required by the circuit. The capacitor voltage rating should be at least 1.25 times greater than the
the output voltage ripple includes the capacitance
voltage drop ∆VCOUT and ESR voltage drop ∆V ESR
maximum input voltage and a voltage rating of 1.5 times
is a conservative guideline. For two-phase converter, the
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
23
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APW7098
Application Information (Cont.)
2
Input Capacitor Selection (Cont.)
Phigh-side = IOUT (1+ TC)(RDS(ON))D + (0.5)( IOUT)(VIN)( tSW)FSW
RMS current of the bulk input capacitor is roughly calculated as the following equation :
Plow-side = IOUT (1+ TC)(RDS(ON))(1-D)
2
IRMS =
where
I
IOUT
× 2D ⋅ (1 - 2D)
2
is the load current
OUT
TC is the temperature dependency of RDS(ON)
FSW is the switching frequency
For a through hole design, several electrolytic capacitors
may be needed. For surface mount design, solid tan-
tSW is the switching interval
D is the duty cycle
talum capacitors can be used, but caution must be exercised with regard to the capacitor surge current rating.
Note that both MOSFETs have conduction losses while
the high-side MOSFET includes an additional transi-
MOSFET Selection
tion loss. The switching interval, t SW , is the function of
The APW7098 requires two N-Channel power MOSFETs
on each phase. These should be selected based upon
the reverse transfer capacitance CRSS. The (1+TC) term is
a factor in the temperature dependency of the RDS(ON) and
can be extracted from the “RDS(ON) vs. Temperature” curve
RDS(ON), gate supply requirements, and thermal management requirements.
of the power MOSFET.
In high-current applications, the MOSFET power
dissipation, package selection, and heatsink are the domi-
Layout Consideration
In any high switching frequency converter, a correct layout
nant design factors. The power dissipation includes two
loss components, conduction loss, and switching loss.
is important to ensure proper operation of the regulator.
With power devices switching at higher frequency, the
The conduction losses are the largest component of
power dissipation for both the high-side and the low-
resulting current transient will cause voltage spike across
the interconnecting impedance and parasitic circuit
side MOSFETs. These losses are distributed between
the two MOSFETs according to duty factor (see the equa-
elements. As an example, consider the turn-off transition
of the PWM MOSFET. Before turn-off condition, the
tions below). Only the high-side MOSFET has switching
losses since the low-side MOSFETs body diode or an
MOSFET is carrying the full load current. During turn-off,
current stops flowing in the MOSFET and is freewheeling
external Schottky rectifier across the lower MOSFET
clamps the switching node before the synchronous rec-
by the low side MOSFET and parasitic diode. Any parasitic
inductance of the circuit generates a large voltage spike
tifier turns on. These equations assume linear voltagecurrent transitions and do not adequately model power
during the switching interval. In general, using short and
wide printed circuit traces should minimize interconnect-
loss due the reverse-recovery of the low-side MOSFET
body diode. The gate-charge losses are dissipated by
ing impedances and the magnitude of voltage spike.
Besides, signal and power grounds are to be kept sepa-
the APW7098 and don’t heat the MOSFETs. However,
large gate-charge increases the switching interval, tSW
rating and finally combined using ground plane construction or single point grounding. The best tie-point between
which increases the high-side MOSFET switching
losses. Ensure that all MOSFETs are within their maxi-
the signal ground and the power ground is at the negative side of the output capacitor on each channel, where
mum junction temperature at high ambient temperature
by calculating the temperature rise according to package
there is less noise. Noisy traces beneath the IC are not
recommended. Figure 10. illustrates the layout, with bold
thermal-resistance specifications. A separate heatsink
may be necessary depending upon MOSFET power,
lines indicating high current paths; these traces must be
short and wide. Components along the bold lines should
package type, ambient temperature and air flow.
For the high-side and low-side MOSFETs, the losses are
be placed lose together. Below is a checklist for your
layout:
approximately given by the following equations:
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
24
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APW7098
Application Information (Cont.)
Layout Consideration (Cont.)
•
Keep the switching nodes (UGATEx, LGATEx, BOOTx,
and PHASEx) away from sensitive small signal nodes
APW7098
since these nodes are fast moving signals. Therefore,
keep traces to these nodes as short as possible and
there should be no other weak signal traces in parallel with theses traces on any layer.
V IN1=V IN
BOOT1
• The signals going through theses traces have both
high dv/dt and high di/dt with high peak charging and
UGATE1
discharging current. The traces from the gate drivers
to the MOSFETs (UGATEx and LGATEx) should be short
•
L1
PHASE1
and wide.
Place the source of the high-side MOSFET and the
LGATE1
drain of the low-side MOSFET as close as possible.
Minimizing the impedance with wide layout plane be-
CSP1
tween the two pads reduces the voltage bounce of
the node. In addition, the large layout plane between
CSN2
CSP2
• For experiment result of accurate current sensing, the
LGATE2
current sensing components are suggested to place
•
CS1
V OUT
CSN1
the drain of the MOSFETs (VIN and PHASEx nodes)
can get better heat sinking.
•
RS1
close to the inductor part. To avoid the noise
interference, the current sensing trace should be away
PHASE2
from the noisy switching nodes.
Decoupling capacitors, the resistor-divider, and boot
UGATE2
capacitor should be close to their pins. (For example,
place the decoupling ceramic capacitor close to the
BOOT2
CS2
L
O
A
D
RS2
L2
drain of the high-side MOSFET as close as possible).
The input bulk capacitors should be close to the drain
of the high-side MOSFET, and the output bulk capacitors should be close to the loads. The input capaci-
VIN2 =V IN
Figure 10. Layout Guidelines
tor’s ground should be close to the grounds of the
output capacitors and low-side MOSFET.
• Locate the resistor-divider close to the FB pin to minimize the high impedance trace. In addition, FB pin
traces can’t be close to the switching signal traces
(UGATEx, LGATEx, BOOTx, and PHASEx).
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
25
www.anpec.com.tw
APW7098
Package Information
QFN4x4-24A
D
b
E
A
Pin 1
A1
D2
A3
L
K
E2
Pin 1
Corner
e
S
Y
M
B
O
L
QFN4x4-24A
MILLIMETERS
INCHES
MIN.
MAX.
MIN.
MAX.
A
0.70
0.80
0.028
0.032
A1
0.00
0.05
0.000
0.002
0.30
0.008
0.012
0.154
0.161
A3
b
0.20 REF
0.18
0.008 REF
D
3.90
4.10
D2
2.00
2.50
0.079
0.098
0.161
0.098
E
3.90
4.10
0.154
E2
2.00
2.50
0.079
0.45
0.014
e
0.50 BSC
L
0.35
K
0.20
K
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
0.020 BSC
0.018
0.008
0.08
0.003
26
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APW7098
Carrier Tape & Reel Dimensions
P0
P2
P1
A
B0
W
F
E1
OD0
K0
A0
A
OD1 B
B
T
SECTION A-A
SECTION B-B
H
A
d
T1
Application
QFN4x4-24A
A
H
330.0±2.00
50 MIN.
P0
P1
4.0±0.10
8.0±0.10
T1
C
12.4+2.00 13.0+0.50
-0.00
-0.20
P2
D0
2.0±0.05
1.5+0.10
-0.00
d
D
1.5 MIN.
20.2 MIN.
W
E1
12.0±0.30 1.75±0.10
F
5.5±0.05
D1
T
A0
B0
K0
1.5 MIN.
0.6+0.00
-0.40
4.30±0.20
4.30±0.20
1.30±
0.20
(mm)
Devices Per Unit
Package Type
QFN4x4-24A
Unit
Tape & Reel
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
Quantity
3000
27
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APW7098
Taping Direction Information
QFN4x4-24A
USER DIRECTION OF FEED
Classification Profile
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
28
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APW7098
Classification Reflow Profiles
Profile Feature
Sn-Pb Eutectic Assembly
Pb-Free Assembly
100 °C
150 °C
60-120 seconds
150 °C
200 °C
60-120 seconds
3 °C/second max.
3°C/second max.
183 °C
60-150 seconds
217 °C
60-150 seconds
See Classification Temp in table 1
See Classification Temp in table 2
Time (tP)** within 5°C of the specified
classification temperature (Tc)
20** seconds
30** seconds
Average ramp-down rate (Tp to Tsmax)
6 °C/second max.
6 °C/second max.
6 minutes max.
8 minutes max.
Preheat & Soak
Temperature min (Tsmin)
Temperature max (Tsmax)
Time (Tsmin to Tsmax) (ts)
Average ramp-up rate
(Tsmax to TP)
Liquidous temperature (TL)
Time at liquidous (tL)
Peak
(Tp)*
package
body
Temperature
Time 25°C to peak temperature
* Tolerance for peak profile Temperature (Tp) is defined as a supplier minimum and a user maximum.
** Tolerance for time at peak profile temperature (tp) is defined as a supplier minimum and a user maximum.
Table 1. SnPb Eutectic Process – Classification Temperatures (Tc)
3
3
Package
Thickness
<2.5 mm
≥2.5 mm
Volume mm
≥350
220 °C
220 °C
Volume mm
<350
235 °C
220 °C
Table 2. Pb-free Process – Classification Temperatures (Tc)
Package
Thickness
<1.6 mm
1.6 mm – 2.5 mm
≥2.5 mm
Volume mm
<350
260 °C
260 °C
250 °C
3
Volume mm
350-2000
260 °C
250 °C
245 °C
3
Volume mm
>2000
260 °C
245 °C
245 °C
3
Reliability Test Program
Test item
SOLDERABILITY
HOLT
PCT
TCT
HBM
MM
Latch-Up
Method
JESD-22, B102
JESD-22, A108
JESD-22, A102
JESD-22, A104
MIL-STD-883-3015.7
JESD-22, A115
JESD 78
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
29
Description
5 Sec, 245°C
1000 Hrs, Bias @ 125°C
168 Hrs, 100%RH, 2atm, 121°C
500 Cycles, -65°C~150°C
VHBM≧2KV
VMM≧200V
10ms, 1tr≧100mA
www.anpec.com.tw
APW7098
Customer Service
Anpec Electronics Corp.
Head Office :
No.6, Dusing 1st Road, SBIP,
Hsin-Chu, Taiwan, R.O.C.
Tel : 886-3-5642000
Fax : 886-3-5642050
Taipei Branch :
2F, No. 11, Lane 218, Sec 2 Jhongsing Rd.,
Sindian City, Taipei County 23146, Taiwan
Tel : 886-2-2910-3838
Fax : 886-2-2917-3838
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Oct., 2011
30
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