MICROSEMI NX2601CMTR

Evaluation board available.
NX2601
DUAL SYNCHRONOUS PWM CONTROLLER WITH NMOS LDO
CONTROLLER & 5V BIAS REGULATOR
PRELIMINARY DATA SHEET
Pb Free Product
DESCRIPTION
The NX2601 controller IC is a triple controller with a dual
channel synchronous Buck controller IC and an LDO controller designed for multiple converters such as PCIe
graphic card applications .The two synchronous PWM
controllers are 180 degree out of phase which reduces
the input ripple current, allowing to reduce the # of input
capacitors.Another main feature of the part is that it can
operate from single 12V supply while maintaining a regulated 5V supply for the biasing and the internal drivers.
Other features of NX2601 are: programmable frequency
from 200kHz to 1MHz, independent digital soft start and
enable pins for each controller which allows for different
power sequencing, Adaptive driver provides optimized efficiency while maintain sufficient deadband, Vcc
undervoltage lock out and current limiting using an Rdson of the external MOSFET with HICCUP feature.
FEATURES
n Two channel PWM with out of phase operation
n Individual digital soft start for two PWM output
and LDO controller
n Bus voltage operation from 2V to 25V
n Hiccup Current limit by sensing Rdson of MOSFET
n Adjustable frequency up to 1Mhz per channel
n Adaptive deadband time
n Three enable pin available allows for independent
power sequencing
n MLPQ-32L package offers small size
n Pb-free and RoHS compliant
APPLICATIONS
n
n
n
PCI Graphic Card on board converters
Vddq Supply in mother board applications
On board DC to DC such as
12V to 3.3V, 2.5V or 1.8V
FPGA and Set Top Box Applications
n
11
REG FB
R13
1.65k
47pF
C16
10
2N3904
5k
M5
VOUT3
+2.5V/2A
R18
1.5k
R15
C18
0
150pF
R16
C19 5k
150uF
R17
2.35k
R19
1.25k
2N3904
ON
R26
10k
7
6.8k
LDRV1
ENLDO
2
R28
10k
M1
L2 0.78uH
R1 10.5k
R2
1.5k
22
M2
21
18
C7
2 x (2R5TPD680M6,680uF,6mohm)
R3
10.4k
C6
2.7nF
R5 5k 8.2nF C5
R4
20.8k
220pF
C8
1uF
+5V
D2
17
C11
0.1uF
16
C9
180uF
M3
LDRV2
R6 6k
M4
19
20
R24 62k
PGND2
C21 1nF
Fb2 12
13
Comp2
GND
VOUT2
+1.8V/10A
15
OCP2 14
VP
31 VREF
VIN1
+12V
VOUT1
+1.2V@15A
26
C22
PVCC2
C3
100uF
C2
180uF
C4
0.1uF
25
Fb1 29
28
SW2
R7
820
C14
3 x (4TPE150M,150uF,18mohm)
R8
8.7k
C13
3.3nF
R10
5k
4
Rev. 2.3
12/01/06
L1 1uH
L4 1.5uH
ENSW2
30
Device
NX2601CMTR
+5V
Comp1
HDRV2
2N3904
6 RT
PATENT PENDING
PGND1
BST2
R21
1.25k
OFF R27 10k
ON
C1
1uF
24
OCP1 27
LDO FB
1 ENSW1
VIN1
HDRV1
SW1
C25
1uF
R20
23
8 LDO OUT
3
OFF R25 10k
BST1
AUXVCC
1uF
PVCC1
D1
REG OUT
9
C24
5
VCC
NX2601
VIN1
C20
150uF
C15
1uF
R12
5k
C17
68uF
VIN2
+3.3V
TYPICAL APPLICATION
R11 10
+5V
C23
C12
R9
6.97k
10nF
220pF
Figure1 - Typical application of 2601
ORDERING INFORMATION
Temperature
0 to 70oC
Package
MLPQ-32L
Frequency
200kHz to 1MHz
Pb-Free
Yes
1
NX2601
ABSOLUTE MAXIMUM RATINGS
Vcc,PVcc & BST to SW voltage ......................... 6.5V
BST Voltage ...................................................... 35V
SW ................................................................... -5V(Note1) to 35V
AUXVCC .......................................................... 35V
All other pins .................................................... GND to Vcc+0.3V
Storage Temperature Range ............................... -65oC to 150oC
Operating Junction Temperature Range ............... -40oC to 125oC
CAUTION: Stresses above those listed in "ABSOLUTE MAXIMUM RATINGS", may cause permanent damage to
the device. This is a stress only rating and operation of the device at these or any other conditions above those
indicated in the operational sections of this specification is not implied.
PACKAGE INFORMATION
HDRV1
SW1
COMP1
OCP1
FB1
VP
NC
VREF
32-LEAD 5x5 PLASTIC MLPQ
32 31 30 29 28 27 26 25
ENSW1 1
24 BST1
ENSW2 2
23 PVCC1
ENLDO 3
22 LDRV1
GND
4
VCC
5
21 PGnd1
NX2601
20 PGnd2
RT 6
19 LDRV2
LDO FB 7
18 PVCC2
θJA ≈ 35o C / W
17 BST2
LDO OUT 8
SW2
HDRV2
OCP2
COMP2
FB2
REG FB
AUXVCC
REG OUT
9 10 11 12 13 14 15 16
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over Vcc = 5V, VBST-VSW =5V, ENSW1=HIGH, ENSW2=HIGH,
ENLDO=HIGH, and T A = 0 to 70oC. Typical values refer to T A = 25oC. Low duty cycle pulse testing is used which
keeps junction and case temperatures equal to the ambient temperature.
PARAMETER
SYM
TEST CONDITION
MIN
TYP
MAX
UNITS
Reference Voltage
VREF 4.5 < Vcc < 5.5
FB Voltage
0.800
V
FB Voltage Line Regulation
0.4
%
Vcc Supply Voltage
VCC
Vcc Voltage Range
5.5
5.0
4.5
V
ICC_STA Outputs not switching
Vcc Static Supply Current
2.0
mA
ICC_DYN Freq=600kHz,
Vcc Dynamic Supply
8
mA
CLOAD = 3300pF
Current
4.
VBST
VBST Voltage Range
5.5
5.0
4.5
V
IBST_STA Outputs not switching
VBST Static Supply Current
2.0
mA
IBST_DYN Freq = 600KHz,
VBST Dynamic Supply
TBD
mA
CLOAD = 3300pF
Current
Rev. 2.3
12/01/06
2
NX2601
PARAMETER
Under Voltage Lockout
UVLO Threshold - Vcc
UVLO Hysteresis - Vcc
UVLO Threshold - VAUXVcc
UVLO Hysteresis - VAUXVcc
Error Amplifiers
Open Loop Gain
Input Bias Current
Input Offset Voltage
Oscillator
Frequency
SYM
VCC_UVLO
VCC__HYST
VAUX_UVLO
VAUX_HYST
FS
Ramp Amplitude
VRAMP
EN & SS
Soft Start Time
TSS
Enable Threshold Voltage
Enable Hysterises
LDO Controller
LDO FB Voltage
FB Pin Bias Current
LDO_out Output Voltage High
LDO_out Output Voltage Low
Open Loop Gain
5V AUX REG
REG FB Voltage
FB Pin Bias Current
REG_out Output Voltage
High
REG_out Output Voltage
Low
Open Loop Gain
High Side driver
(CL=3300pF)
Output Impedance, Sourcing
Current
Output Impedance , Sinking
Current
Rise Time
Fall Time
Deadband Time
Rev. 2.3
12/01/06
TEST CONDITION
MIN
Supply Ramping Up
Supply Ramping Down
Supply Ramping Up
Supply Ramping Down
Rt=30k,measured at the
output drive
Fs=600KHz
Enable ramp up
LDOOUT=LDOFB
AUXVCC=24V,LDO FB=0.7V
IO_SOURCE=1.4mA
AUXVCC=24V,LDO FB=0.9V
IO_SINK=1.4mA
GBNT(Note2)
-0.2
22
Rsource_H
-0.2
22
MAX
UNITS
4
0.2
7
0.7
V
V
V
V
65
0.3
0
dB
uA
mV
600
KHz
1
V
3.41
1.25
100
mS
V
mV
0.8
0
23.5
V
µA
V
0.2
V
dB
50
REGOUT=REGFB
AUXVCC=24V,REG FB=1.1V
IO_SOURCE=1.4mA
AUXVCC=24V,REG FB=1.4V
IO_SINK=1.4mA
GBNT(Note2)
TYP
1.25
0
23.5
V
µA
V
0.2
V
dB
50
0.85
ohm
0.65
25
20
30
ohm
ns
ns
ns
R sink_H
THDRV_RISE 10% to 90%
THDRV_FALL 90% to 10%
TDEAD_LH LDRV going Low to HDRV
going High, 10% to 10%
3
NX2601
PARAMETER
Low Side driver
(CL=3300pF)
Output Impedance, Sourcing
Current
Output Impedance , Sinking
Current
Rise Time
Fall Time
Deadband Time
SYM
TEST CONDITION
MIN
TYP
MAX
UNITS
Rsource_L
0.85
ohm
0.5
25
20
20
ohm
ns
ns
ns
R sink_L
TLDRV_RISE 10% to 90%
TLDRV_FALL 90% to 10%
TDEAD_HL SW going Low to LDRV going
High, 10% to 10%
Note 1: 500ns transient. This pin can withstand -2V DC.
Note 2: This parameter is guaranteed by design but not tested in production(GBNT).
Rev. 2.3
12/01/06
4
NX2601
PIN DESCRIPTIONS
PIN #
PIN SYMBOL
1
ENSW1
2
ENSW2
3
ENLDO
4
GND
Analog ground.
5
VCC
IC's supply voltage. This pin biases the internal logic circuits. A high freq 1uF
ceramic capacitor is placed as close as possible to and connected to this pin and
ground pin.
6
RT
7
LDO FB
8
LDO OUT
9
AUXVCC
10
REGOUT
RER
11
REGFB
12
FB2
29
FB1
13
COMP2
28
COMP1
Rev. 2.3
12/01/06
PIN DESCRIPTION
A resistor divider is connected from the respective switcher BUS voltages to these
pins that holds off the controllers soft start until this threshold is reached. An
external low cost MOSFET or NPN transisitor can be connected to this pin for
external enable control.
A resistor divider is connected from the LDO bus voltage to this pin that holds off
the LDO soft start until this threshold is reached. An external low cost MOSFET
can be connected to this pin for external enable control.
Oscillator's frequency can be set by using an external resistor from this pin to
GND. This frequency is the master clock frequency which is internally divided by
two to set each controller frequency.
LDO controller feedback input. If the LDOFB pin is pulled below 0.5*Vref, an
internal comparator after certain delay and pulls down LDOOUT pin and initiates
the HICCUP circuitry. During the startup this latch is not activated, allowing the
LDOFB pin to come up and follow the Soft started Vref voltage.
LDO controller output. This pin is controlling the gate of an external NCH
MOSFET. The maximum rating of this pin is 16V.
This pin is the supply voltage for the LDO controller as well as the 5V regulator
controller that regulates the voltage at Vcc derived from the BUS voltage. The
maximum voltage applied to this pin is 30V.
The output of the 5V regulator controller that drives a low current low cost external
BIPOLAR transistor or an external MOSFET to regulate the voltage at Vcc pin
derived from BUS voltage. This eliminates an otherwise external regulator needed
in applications where 5V is not available.
Feedback pin of the 5V regulator controller. A resistor divider is connected from
the output of the 5V regulator to this pin to complete the loop.
This pin is the error amplifiers inverting input. These pins are connected via
resistor dividers to the output of the switching regulators to set the output DC
voltage.
These pins are the outputs of error amplifiers and are used to compensate the
respective voltage control feedback loops.
5
NX2601
PIN DESCRIPTIONS
PIN #
PIN SYMBOL
14
OCP2
27
OCP1
15
SW2
26
SW1
16
25
HDRV2
HDRV1
17
BST2
24
BST1
18
PVCC2
23
PVCC1
19
22
LDRV2
LDRV1
Low side gate driveroutputs.
20
21
PGND2
PGND1
Powerground pinforlow sidedrivers.
30
VP
31
VREF
32
NC
Rev. 2.3
12/01/06
PIN DESCRIPTION
This pin is connected to the drain of the external low side MOSFET and is the
input of the over current protection(OCP) comparator. An internal current source
which equals 1.25V divided by Rt resistor is flown to the external resistor which
sets the OCP voltage across the Rdson of the low side MOSFET. Current limit
point is this voltage divided by the Rds-on. Once this threshold is reached the
Hdrv and Ldrv pins are switched low and an internal hiccup circuit is set that
recycles the soft start circuit after 2048 switching cycles.
Thesepinsareconnected tosourceofhighside FETsandprovide return path for
the high side drivers.Theyare also used to hold the low side driverslow untilthis
pin is broughtlow by the action ofhigh side turning off.LDRVs can only go high if
SW is below 1V threshold .
Highside gate driveroutputs.
Thispin suppliesvoltage to highside FET driver.A high freq 1uF ceram iccapacitoris placed as close as possible to and connected to these pins and respected
SW pins.
Supplyvoltage forthe low side fetdrivers.A high frequency1uF ceram iccapm ust
be connected from this pin to the PGND1 and PGND2 pin as close as possible to
the pins.
Thispin isthe firsterroram plifiernon-inverting input.Thispin shouldbeconnected eithertoanexternalreferencevoltage (tracking application)orto the
internalreferencevoltageprovidedbythisdevice.
Referencevoltage available.A 100pFcapacitorcan be connected from thispin to
GND.This pin is held low untilinternalVccUVLO and the ENSW 1 pin are good,
allowing itto softstart.
6
NX2601
BLOCK DIAGRAM
AUXVCC
Bias
REGFB
9.6/9.2
UVLO
POR_LDO
REGOUT
VCC
Bias
Generator
1.25V
4/3.8
0.8V
UVLO
POR_SW
BST1
Vref
ENSW1
DRVH1
1.25/1.15
two phase
OSC
RT
VP
Digital
start Up
SW1
set1
Control
Logic
ramp1
PVCC1
S
R
Q
POR_SW
DRVL1
FB1
PGND1
COMP1
OCP1
Channel 1 PWM Controller
OCP
comparator
BST2
ENSW2
Channel 2 PWM controller (exclude oscillator)
FB2
COMP2
DrvH2
SW2
PVCC2
DrvL2
PGND2
OCP2
ENLDO
1.25/1.15
POR_LDO
GND
Rev. 2.3
12/01/06
LDO
control
logic
digital
start up
0.4
LDOOUT
FBLDO
7
NX2601
R19 10
VIN1
VIN3
+3.3V
VOUT3
+2.5V/2A
11
REG FB
R15
1.65k
C7
47pF
C8
33uF
C10
1uF
R16
5k
C17
68uF
R13
5k
10
Q2
9
C5
150uF
M5
C4
150uF
R10
150pF
R11
5k
R6
2.35k
7
3
REG OUT
AUXVCC
HDRV1
VIN1
ENLDO
ENSW1
PGND1
C11
0.1uF
25
2
VIN2
PVCC2
HDRV2
ENSW2
R3
1.25k
SW2
Q4
R22 10.5k
C24
1uF
C23
180uF
VIN1
+12V
C21
39uF
L1 0.78uH
R23
20k
22
Q5
21
18
5k
8.2nF
R24
C17
C12
470pF
R26
1.5k
C19
2.7nF
C13,C14
680uF,6mohm
VOUT1
+1.2V@15A
R27
10.4k
R25
20.8k
220pF
C18
C42
1uF
+5V
17
LDRV2
R2 62k
PGND2
VP
Q6
15
R32 3k
L4 1uH
Q7
20
R33
5k
31 VREF
GND
C32
C38
1uF
C36
180uF
L3 1.5uH
R34
20k
19
Fb2 12
13
Comp2
R1
1k
C31
0.1uF
16
OCP2 14
6 RT
30
L2 1uH
26
Fb1 29
28
Comp1
BST2
R9
C2 100pF
+5V
VIN2
+5V
D2
R4
1.25k
C1 100pF
C41
1uF
24
OCP1 27
LDO FB
R5
1.25k
1
2.7k
BST1
LDRV1
R8
6.8k
23
D1
SW1
R7
1.5k
PVCC1
8 LDO OUT
C3
0
5
VCC
NX2601
+5V
C34
470pF
R28
330
C33
39uF
VOUT2
+1.8V@10A
C26,27,28
150uF,18mohm
R29
3.5k
C25
8.2nF
C37
10nF
R35
2.7k
220pF
4
Simplified Demo board schematic
Rev. 2.3
12/01/06
8
NX2601
TP3
Q3
J6
R 19
J7
1
OP
1
SW 1
SW 2
0
0
TP4
1u
TP7
C9
R 1 6 6 T P B 68M U 1
L2
Vcc1
4.99k
VCC
R 13
24
R 20
0
C7
M T D 3055E R 1 2
8
OCP1
AUX_VCC
LDO_OUT
0
C3
150pf
32
NC
R 10
0
R 11
7
C4
R6
4 T P E 150M
2.35k
.1u
L D O _ IN
R7
3
LD O _O U T
PGND1
Fb1
Comp1
1
14
5
15
R9
6
16
L D O _ IN
17
TP6
R2
C1
SW2
2
18
9
19
S W 1 _ IN 10
EN_SW2
OCP2
20
S W 2 _ IN
C 35
C 33
OP
16S V P A 39M A A
16S V P A 180M
4
0
Q6
IR F 7822
SW2
15
14
R 32
C 30
6
0
Rt
4
Vp
PGND2
Fb2
20
1u
3.5k
100p
C 32
Vref
220p
Comp2
13
S W 2 _ IN
J5
R 29
12
1k
31
op
470p
IR F 7822
R1
C2
C 26 C 27 C 28 C 29
C 34
Q7
1
2
DO5010P-222HC
PVC C
C 42
30
SW2_OUT
20k
R 31
19
Ldrv 2 18
PVCC2
J3
L3
R 34
3k
op
100p
1k
R 30
16
C 31
62k
17
8
C 36
C 38
1u
PVC C
R 33
C 37
10n
R 35
2.7k
1
R 28
C 25
330
8.2nF
4.99k
C 40
.1u
PACKAGE:MLPQ32L
4
7
L4
DO1603C-102
D2
Hdrv 2
1.25k
R 36
S W 2 _ IN
20.8k
Vcc2
EN_SW1
AGND
S W 2 _ IN
13
TP5
4.99k
R3
4
2.7n
.1u
2.7k
J8
3
1.5k
.1u
5
4
3
2
S W 2 _ IN
12
C 19
4T P E 150M
R8
1.25k
2
R 26
C 39
R 25
8.2n
R 24
28
R4
L D O _ IN
C 18
220p
BST2
6.8k
L D O _ IN
10.4k
29
J4
1
D 1N 5819
S W 1 _ IN
11
R 27
1u
C 17
1.25k
1
470p
4T P E 150M
1
2
C 12
C 41
21
EN_LDO
R5
IR F 3706
PVC C
1.5k
J9
0
1
2
C 13 C 14 C 15 C 16
20k
R 21
4T P E 150M
C6
LDO_FB
C 20
R 23
1
2
3
2
3
4
5
4.99k
Q5
10.5k
8
7
6
5
1
op
22
Ldrv 1 23
PVCC1
SW1_OUT
DO5010P-781HC
R 22
27
J2
L1
O p
Q1
REG_OUT
IR F 3706
8
7
6
5
9
N X 2601_M L P Q
10
C5
4TP E 150M
SW1
SW1
26
5
4
3
2
25
2R 5T P D 680M 6
Hdrv 1
47p
TP2
C 21
16S V P A 39M A A
Q4
.1u
R 15
LD O _O U T
C 22
16S V P A 180M
OP
D 1N 5819
C 11
1.65k
J1
1u
PVC C
R 14
0
C 23
C 24
D1
BST1
2R 5T P D 680M 6
4.99k
L D O _ IN
REG_Fb
1
2
3
TP1
11
S W 1 _ IN
DO1603C-102
O P
Q2
C 8 2N3904
16TQ C 33M
C 10
PVC C
2
3
4
5
R 18
5
S W 1 _ IN
R 17
2
3
4
5
10
Size
Document Number
Date:
T h u rsday, M a rc h 2 4 , 2 0 0 5Sheet
S W 2 _ IN
Rev
A
NX2601-02EVL BRD SCHEMATIC
1
of
1
Figure 2 - Demo board schematic based on ORCAD
Rev. 2.3
12/01/06
9
NX2601
Bill of Materials
Item number
Quantity
1
2
3
4
5
6
7
8
9
10
11
Rev. 2.3
12/01/06
2
1
5
5
1
1
1
5
2
2
9
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
2
1
1
2
2
1
1
2
5
3
1
1
2
1
1
1
2
2
1
1
3
1
2
1
2
8
38
39
40
41
42
43
44
45
46
47
48
49
5
1
1
1
2
1
1
1
1
1
1
7
50
1
C2,C1
C3
C4,C5,C26,C27,C28
C6,C11,C31,C39,C40
C7
C8
C9
C10,C24,C38,C41,C42
C12,C34
C14,C13
Q3,R14,C15,C16,C20,C22,
C29,C30,C35
C17,C32
C18
C19
C21,C33
C36,C23
C25
C37
D1,D2
J1,J4,J5,J6,J7
J2,J3,J9
J8
L1
L2,L4
L3
Q1
Q2
Q4,Q5
Q7,Q6
R1
R2
R3,R4,R5
R6
R7,R26
R8
R35,R9
R10,R12,R17,R18,R20,R21,
R30,R31
R11,R13,R16,R24,R33
R15
R19
R22
R34,R23
R25
R27
R28
R29
R32
R36
TP1,TP2,TP3,TP4,TP5,TP6,
TP7
U1
Value
100p
150pf
4TPE150M
.1u
47p
16TQC33M
6TPB68M
1u
470p
2R5TPD680M6
OP
220p
8.2n
2.7n
16SVPA39MAA
16SVPA180M
8.2nF
10n
D1N5819
SCOPE TP
CON2
CON20B
DO5010P-781HC
DO1603C-102
DO5010P-222HC
MTD3055E
2N3904
IRF3706
IRF7822
1k
62k
1.25k
2.35k
1.5k
6.8k
2.7k
0
Manufacture
SANYO
SANYO
SANYO
SANYO
SANYO
SANYO
Tektronics
Coilcraft
International Rectifier
International Rectifier
4.99k
1.65k
10
10.5k
20k
20.8k
10.4k
330
3.5k
3k
10k
TP
NX2601_MLPQ
NEXSEM INC.
10
NX2601
Demoboard waveforms
Figure 3 - Start up waveform of VCC by internal regulator.
Ch1(AUXVCC), Ch3( VCC&PVCC)
Figure 6 - Output ripple for power output CH1 and CH2
Figure 4 - Soft start for Channel 1 1.2V and chanel 2
1.8V output
Figure 7-Transient response for first channel 1.2V output
Figure 5 - Soft start for Channel 1 1.2V and LDO output
Figure 8 -Transient reponse for Channel 1. (zoomed)
Rev. 2.3
12/01/06
11
NX2601
Demo Board Waveforms (Cont')
Figure 9 - Ch2 1.8V output transient 0 to 9A.
Figure 12 - Ch1 is short. All channels go into hiccup.
Figure 10 - Ch2 1.8V transient (zoomed)
Figure 13 - Ch2 is in short. All channels are in hiccup.
Figure 11 - Transient response for 2.5V LDO output
Rev. 2.3
12/01/06
Figure 14 - LDO in short. All channels go into hiccup.
12
NX2601
APPLICATION INFORMATION
Symbol Used In Application Information:
VIN
- Input voltage
VOUT
- Output voltage
IOUT
- Output current
=
DVRIPPLE - Output voltage ripple
FS
∆IRIPPLE =
VIN -VOUT VOUT
1
×
×
L OUT
VIN
FS
12V-1.2V 1.2V
1
×
×
= 4.6A
0.78uH
12V 300kHz
...(2)
Output Capacitor Selection
- Switching frequency
Output capacitor is basically decided by the
DIRIPPLE - Inductor current ripple
amount of the output voltage ripple allowed during steady
state(DC) load condition as well as specification for the
Design Example
load transient. The optimum design may require a couple
Power stage design requirements:
VOUT=1.2V
of iterations to satisfy both condition.
Based on DC Load Condition
The amount of voltage ripple during the DC load
IOUT =15A
condition is determined by equation(3).
VIN=12V
DVRIPPLE<=20mV
∆VRIPPLE = ESR × ∆IRIPPLE +
DVTRAN<=100mV @ 15A step
FS=300kHz
∆IRIPPLE
8 × FS × COUT ...(3)
Where ESR is the output capacitors' equivalent
series resistance,COUT is the value of output capacitors.
Output Inductor Selection
Typically when large value capacitors are selected
The selection of inductor value is based on induc-
such as Aluminum Electrolytic,POSCAP and OSCON
tor ripple current, power rating, working frequency and
types are used, the amount of the output voltage ripple
efficiency. Larger inductor value normally means smaller
is dominated by the first term in equation(3) and the
ripple current. However if the inductance is chosen too
second term can be neglected.
large, it brings slow response and higher cost. Usually
For this example, POSCAP are chosen as output
the ripple current ranges from 20% to 40% of the output
capacitors, the ESR and inductor current typically de-
current. This is a design freedom which can be decided
termines the output voltage ripple.
by design engineer according to various application requirements. The inductor value can be calculated by using
ESR desire =
the following equations:
∆VRIPPLE 20mV
=
= 4.3m Ω
∆IRIPPLE
4.6A
...(4)
If low ESR is required, for most applications, mul-
V -V
V
1
L OUT = IN OUT × OUT ×
∆IRIPPLE
VIN
FS
IRIPPLE =k × IOUTPUT
tiple capacitors in parallel are better than a big capaci...(1)
where k is between 0.2 to 0.4.
Select k=0.3, then
12V-1.2V 1.2V
1
×
×
0.3 × 15A 12V 300kHz
L OUT =0.8uH
L OUT =
Choose LOUT=0.78uH, then coilcraft inductor
DO5010P-781HC is a good choice.
Current Ripple is calculated as
tor. For example, for 20mV output ripple, POSCAP
2R5TPD680M6 with 6mΩ are chosen.
N =
E S R E × ∆ IR I P P L E
∆ VR IPPLE
...(5)
Number of Capacitor is calculated as
N=
6m Ω × 4.6A
20mV
N =1.38
The number of capacitor has to be round up to a
integer. Choose N =2.
Rev. 2.3
12/01/06
13
NX2601
If ceramic capacitors are chosen as output capacitors, both terms in equation (3) need to be evaluated
to determine the overall ripple. Usually when this type of
capacitors are selected, the amount of capacitance per
single unit is not sufficient to meet the transient specification, which results in parallel configuration of multiple
capacitors.
Based On Transient Requirement
Typically, the output voltage droop during transient
is specified as
∆V droop < ∆V tran @step load DISTEP
During the transient, the voltage droop during the
transient is composed of two sections. One section is
dependent on the ESR of capacitor, the other section is
a function of the inductor, output capacitance as well as
tiple capacitor in parallel. The number of capacitors can
be calculated by the following
N=
where τ is the a function of capacitor, etc.
0 if L ≤ L crit

τ =  L × ∆Istep
− ESR × COUT
 V
 OUT
if
L ≥ L crit
...(7)
where
L crit =
ESR × COUT × VOUT ESR E × C E × VOUT
=
...(8)
∆Istep
∆Istep
where ESRE and CE represents ESR and capacitance of each capacitor if multiple capacitors are used
in parallel.
The above equation shows that if the selected output inductor is smaller than the critical inductance, the
voltage droop or overshoot is only dependent on the ESR
...(9)
if
L ≥ L crit
...(10)
sient is 100mV for 15A load step.
If the POSCAP 2R5TPD680M6 (680uF, 6mohm
ESR) is used, the crticial inductance is given as
L crit =
ESR E × C E × VOUT
=
∆I step
6mΩ × 680µF × 1.2V
= 0.33µH
15A
enough, the overshoot can be estimated as the following
...(6)
VOUT
× τ2
2 × L × C E × ∆Vtran
For example, assume voltage droop during tran-
sient load, if assuming the bandwidth of system is high
VOUT
× τ2
2 × L × COUT
+
0 if L ≤ L crit

τ =  L × ∆Istep
− ESR E × CE
 V
 OUT
when load from high load to light load with a DISTEP tran-
∆Vovershoot = ESR × ∆Istep +
∆Vtran
where
input, output voltage. For example, for the overshoot
equation.
ESR E × ∆Istep
The selected inductor is 0.78uH which is bigger
than critical inductance. In that case, the output voltage
transient not only dependent on the ESR, but also capacitance.
number of capacitors is
τ=
=
L × ∆Istep
VOUT
− ESR E × CE
0.78µH × 15A
− 6mΩ× 680µF = 5.67us
1.2V
N=
ESR E × ∆Istep
∆Vtran
+
VOUT
× τ2
2 × L × CE × ∆Vtran
6mΩ × 15A
+
100mV
1.2V
× (5.67us) 2
2 × 0.78µH × 680µF × 100mV
= 1.3
=
of output capacitor. For low frequency capacitor such
The number of capacitors has to satisfied both ripple
as electrolytic capacitor, the product of ESR and ca-
and transient requirement. Overall, we can choose N=2.
pacitance is high and L ≤ L crit is true. In that case, the
It should be considered that the proposed equa-
transient spec is likely to dependent on the ESR of ca-
tion is based on ideal case, in reality, the droop or over-
pacitor.
shoot is typically more than the calculation. The equa-
For most cases, the output capacitors are mul-
tion gives a good start. For more margin, more capacitors have to choose after the test. Typically, for high
Rev. 2.3
12/01/06
14
NX2601
frequency capacitor such as high quality POSCAP es-
where FZ1,FZ2,FP1 and FP2 are poles and zeros in
pecially ceramic capacitor, 20% up 100% (for ceramic)
the compensator. Their locations are shown in figure 15.
more capacitors have to be chosen since the ESR of
The transfer function of type III compensator is
capacitors is so low that the PCB parasitics can affect
given by:
the results tremendously. More capacitors have to be
(1+ sR4 × C2 ) × [1+ s(R2 + R3 ) × C3 ]
Ve
1
=
×
VOUT sR2 × (C2 + C1) (1+ sR × C2 × C1 ) × 1+ sR × C
(
4
3
3)
C2 + C1
selected to compensate these parasitic parameters.
Compensator Design
Due to the double pole generated by LC filter of the
power stage, the power system has 180o phase shift ,
and therefore, is unstable by itself. In order to achieve
accurate output voltage and fast transient response,
Zin
Zf
C1
Vout
compensator is employed to provide highest possible
bandwidth and enough phase margin.Ideally,the Bode
R3
R2
plot of the closed loop system has crossover frequency
between1/10 and 1/5 of the switching frequency, phase
C3
C2
R4
Fb
margin greater than 50o and the gain crossing 0db with -
Ve
20db/decade. Power stage output capacitors usually
R1
decide the compensator type. If electrolytic capacitors
Vref
are chosen as output capacitors, type II compensator
can be used to compensate the system, because the
zero caused by output capacitor ESR is lower than crossover frequency. Otherwise type III compensator should
A. Type III compensator design
For low ESR output capacitors, typically such as
Sanyo OSCON and POSCAP, the frequency of ESR zero
Gain(db)
be chosen.
power stage
FLC
40dB/decade
caused by output capacitors is higher than the crossover frequency. In this case, it is necessary to compensate the system with type III compensator. The following figures and equations show how to realize the type III
loop gain
FESR
compensator by voltage mode amplifier.
1
FZ1 =
2 × π × R 4 × C2
20dB/decade
...(11)
compensator
FZ2 =
1
2 × π × (R 2 + R3 ) × C3
...(12)
FP1 =
1
2 × π × R3 × C3
...(13)
FP2 =
1
2 × π × R4 ×
C1 × C2
C1 + C2
...(14)
FZ1 FZ2
FO FP1
FP2
Figure 15 - Type III compensator and its bode plot
Rev. 2.3
12/01/06
15
NX2601
The crossover frequency usually is selected as
F LC <F O <F ESR, and F O <=1/10~1/5F s for type III
1
2 × π × FZ1 × R 4
C2 =
compensator .
1.Calculate the location of LC double pole
FLC and ESR zero FESR .
FLC =
1
2 × π × L OUT × COUT
1
=
2 × π × 0.78uH × 1320uF
= 4.89kHz
FESR =
1
2 × π × 0.75 × 4.89kHz × 5k Ω
= 8.8nF
=
Choose C2=8.2nF
6. Calculate C 1 by equation (14) with pole F p2 at
half the swithing frequency.
1
2 × π × ESR × COUT
1
2 × π × 3m Ω × 1360uF
= 39kHz
1
2 × π × R 4 × FP 2
C1 =
1
2 × π × 5k Ω × 150kHz
= 212pF
=
=
Choose C1=220pF
7. Calculate R 3 by equation (13).
2.Set R2 equal to10.4kΩ.
R1 =
R2 × VREF
10.4kΩ × 0.8V
=
= 20.8k Ω
VOUT -VREF
1.2V-0.8V
Choose R1= 20.8kΩ.
3. Set zero FZ2 = FLC and Fp1 =FESR .
4. Calculate R4 and C3 with the crossover frequency
smaller than 1/10~ 1/5 of the swithing frequency. Set
FO=25kHz.
1
1
1
C3 =
×(
)
2 × π × R2
Fz2 Fp1
1
1
1
=
×(
)
2 × π × 10.4kΩ
4.89kHz 39kHz
=2.8nF
Choose C3=2.7nF.
V
2 × π × FO × L
R4 = OSC ×
× Cout
Vin
C3
1V 2 × π × 25kHz × 0.8uH
×
× 1360uF
12V
2.7nF
=5.3kΩ
=
Choose R4=5k
5. Calculate C2 with zero Fz1 at 75% of the LC
double pole by equation (11).
Rev. 2.3
12/01/06
R3 =
1
2 × π × FP1 × C3
1
2 × π × 39kHz × 2.7nF
= 1.5k Ω
Choose R3= 1.5kΩ.
=
B. Type II compensator design
If the electrolytic capacitors are chosen as power
stage output capacitors, usually the Type II compensator can be used to compensate the system.
Type II compensator can be realized by simple
RC circuit as shown in figure 16.R3 and C1 introduce a
zero to cancel the double pole effect. C2 introduces a
pole to suppress the switching noise. The following equations show the compensator pole zero location and constant gain.
Gain=
R3
R2
... (15)
Fz =
1
2 × π × R3 × C1
... (16)
Fp =
1
2 × π × R3 × C2
... (17)
16
NX2601
FLC =
C2
Vout
C1
R3
1
2 × π × L OUT × COUT
1
=
R2
2 × π × 1.5uH × 4500uF
= 1.94kHz
Fb
Ve
R1
Vref
FESR =
1
2 × π × ESR × COUT
1
2 × π × 6.33m Ω × 4500uF
= 5.6kHz
=
Gain(db)
power stage
2.Set crossover frequency FO=20kHz>>FESR.
3. Set R2 equal to10kΩ. Based on output voltage,
40dB/decade
using equation 18, the final selection of R 1 is 20kΩ.
4.Calculate R3 value by the following equation.
loop gain
R3=
20dB/decade
VOSC
2 × π × FO × L
×
× R2
V in
ESR
1V
2 × π × 20kHz × 1.5uH
×
× 10kΩ
12V
6.33m Ω
=24.8kΩ
=
Choose R 3 =24.8kΩ.
compensator
Gain
5. Calculate C1 by setting compensator zero FZ
at 75% of the LC double pole.
FZ FLC FESR FO FP
1
2 × π × R3 × Fz
C1=
1
2 × π × 24.8kΩ × 0.75 × 1.94kHz
=4.4nF
=
Figure 16 - Type II compensator and its bode plot
For type II compensator, FO has to satisfy
FLC<FESR<<FO<=1/10~1/5Fs.
The following parameters are used as an ex-
Choose C1=4.7nF.
6. Calculate C 2 by setting compensator pole Fp
at half the swithing frequency.
ample for type II compensator design, three 1500uF
with 19mohm Sanyo electrolytic CAP 6MV1500WGL
are used as output capacitors. Coilcraft DO5010P152HC 1.5uH is used as output inductor. The other
power stage information is that:
VIN=12V, VOUT=1.2V, IOUT =15A, FS=200kHz.
1.Calculate the location of LC double pole F LC
C2=
1
π × R 3 × Fs
1
π × 2 4 .8k Ω × 2 0 0 k H z
=64pF
=
Choose C2=68pF
and ESR zero FESR.
Rev. 2.3
12/01/06
17
NX2601
Output Voltage Calculation
Output voltage is set by reference voltage and
pacitors supply current to the MOSFETs. Usually 1uF
ceramic capacitor is chosen to decouple the high fre-
external voltage divider. The reference voltage is fixed
quency noise. The bulk input capacitors are decided by
at 0.8V. The divider consists of two ratioed resistors
voltage rating and RMS current rating. The RMS current
so that the output voltage applied at the Fb pin is 0.8V
in the input capacitor can be calculated
when the output voltage is at the desired value. The
following equation and picture show the relationship
between
VOUT , VREF and voltage divider..
R 1=
R 2 × VR E F
V O U T -V R E F
...(18)
where R2 is part of the compensator, and the
value of R1 value can be set by voltage divider.
Choose R2=10kΩ, to set the output voltage at
1.8V, the result of R1 is 8kΩ.
IRMS = IOUT × D × 1- D
D=
VOUT
VIN
...(19)
VIN = 12V, VOUT=1.2V, IOUT=15A, using equation
(19), the result of input RMS current is 4.5A.
For higher efficiency, low ESR capacitors are
recommended.
Two Sanyo OS-CON SVPA180M 16V 180uF
29m O with 3.4A RMS rating are chosen as input bulk
capacitors.
Vout
Power MOSFETs Selection
R2
Fb
The NX2601 requires two N-Channel power
MOSFETs. The selection of MOSFETs is based on
R1
maximum drain source voltage, gate source voltage,
Vref
maximum current rating, MOSFET on resistance and
power dissipation. The main consideration is the power
Voltage divider
loss contribution of MOSFETs to the overall converter
efficiency. In this design example, two IRFR3706 are
Figure 17 - Voltage divider
In general, the minimum output load impedance
including the resistor divider should be less than 5kΩ to
prevent overcharge the output voltage by leakage current (e.g. Error Amplifier feedback pin bias current). A
minimum load for 5kΩ less (<1/16w for most of application) is recommended to put at the output. For example,
in this application,
Vout=1.6V
The power loss is 1/16W less
RLOAD = 1.6V × 1.6V /(1/16W) = 40Ω
Select minimum load is 1kΩ should be good
enough.
Input Capacitor Selection
Input capacitors are usually a mix of high frequency
ceramic capacitors and bulk capacitors. Ceramic ca-
used. They have the following parameters: VDS=30V, ID
=75A,RDSON =9mΩ,QGATE =23nC.
There are three factors causing the MOSFET power
loss:conduction loss, switching loss and gate driver loss.
Gate driver loss is the loss generated by discharging the gate capacitor and is dissipated in driver circuits.
It is proportional to frequency and is defined as:
Pgate = (QHGATE × VHGS + QLGATE × VLGS ) × FS
...(20)
where QHGATE is the high side MOSFETs gate
charge,QLGATE is the low side MOSFETs gate charge,VHGS
is the high side gate source voltage, and VLGS is
the low side gate source voltage.
According to equation (3), PGATE =0.07W. This
power dissipation should not exceed maximum power
dissipation of the driver device.
Conduction loss is simply defined as:
pacitors bypass the high frequency noise, and bulk ca-
Rev. 2.3
12/01/06
18
NX2601
The start up of NX2601 can be programmed through
PHCON =IOUT 2 × D × RDS(ON) × K
resistor divider at Enable pin. For example, for channel
PLCON =IOUT 2 × (1 − D) × RDS(ON) × K
...(21)
PTOTAL =PHCON + PLCON
1, if the input bus voltage is 12V and we want NX2601
starts when Vbus is above 8V. We can select
where the RDS(ON) will increases as MOSFET junc-
R2=1.24k
tion temperature increases, K is RDS(ON) temperature
(8V − 1.25V) × R 2
= 6.8k Ω
1.25V
dependency. As a result, RDS(ON) should be selected for
R1 =
the worst case, in which K equals to 1.4 at 125oC
The NX2601 can be turned off by pulling down the
according to IRFR3706 datasheet. Using equation (4),
ENable pin by extra signal MOSFET as shown in the
the result of PTOTAL is 0.54W. Conduction loss should
above Figure. When Enable pin (ENSW1) is below 1.15V,
not exceed package rating or overall system thermal
the digital soft start is reset to zero. In addition, all the
budget.
high side is off and output voltage is turned off.
Switching loss is mainly caused by crossover conduction at the switching transition. The total switching
loss can be approximated.
Frequency Selection
The frequency can be set by external Rt resistor.
1
× VIN × IOUT × TSW × FS
...(22)
2
where IOUT is output current, T SW is the sum of T R and
TF which can be found in mosfet datasheet, and F S is
switching frequency. The result of PSW is 1.5W.
Swithing loss PSW is frequency dependent.
PSW =
The relationship between frequency and RT pin is shown
as follows.
Frequency(kHz) vs. RT
amplifier starts to increase, the feedback network will
0
Soft Start and Enable
NX2601 has two switching controller and one LDO
controller. Each of them has individual digital soft start.
Each channel has one enable pin for start up. When the
Power Ready (POR) signal is high and the voltage at
enable pin is above 1.25V, the internal digital counter
Frequency(khz)
starts to operate and the voltage at positive input of Error
900
800
700
600
500
400
300
200
100
20
force the output voltage follows the reference and starts
the output slowly. After 2048 cycles, the soft start is
30
40
50
60
70
Rt(kohm)
complete and the output voltage is regulated to the desired voltage decided by the feedback resistor divider
Figure 19 - Frequency versus Rt resistor
+
Vbus
For example, for 300kHz operation, Rt is about
POR
OFF
R1
ENSW1
ON
R2
1.25/1.15
Digital
start
up
10k
Figure 18 - Enable and Shut down the NX2601
with Enable pin.
Rev. 2.3
12/01/06
62kohm.
Over Current Limit Protection
Over current limit for step down converter is
achieved by sensing current through the low side
19
NX2601
MOSFET. Inside NX2601, the current through Rt pin is
important is that MOSFET has to be selected right pack-
mirrored and injecting to the pin OCP. Since the current
age to handle the thermal capability. For LDO, maxi-
through Rt pin is decided as
mum power dissipation is given as
1 .2 5
R t
IR T =
This current is very accurate and does not change
with silicon process and temperature, the over current
PLOSS = (VLDOIN − VLDOOUT ) × I LOAD
= (3.3V − 2.5V) × 2A = 1.6W
Select IR MOSFET IRFR3706 with 9mΩ RDSON is
sufficient.
limit tripping point can be set more accurate than traditional current source. This scheme is the property of
LDO Compensation
Nexsem. When synchronous FET is on, the voltage at
node SW is given as
VSW =-IL × RDSON
The voltage at pin OCP is given as
IOCP × ROCP +VSW
The diagram of LDO controller including VCC regulator is shown in above figure 20. For low frequency
capacitor such as electrolytic, POSCAP, OSCON, etc,
The compensation parameter can be calculated as follows.
When the voltage is below zero, the over current
CC =
occurs. The over current limit can be set by the following
g × ESR
1
× m
2 × π × FO × R f1 1+gm × ESR
where FO is the desired loop gain.
equation
ISET = IRT × ROCP /RDSON
For example, For 20A current limit and 9mohm
Rdson for IRFR3706, the OCP set resistor is calculated
as
I RT =
+
LDO input
Vref
Rf1
1.25V
= 20uA
62k
ESR
Rf2
Rc
R OCP =
ISET
20A
× R DSON =
× 9mohm = 9kohm
I RT
20uA
Rload
Cc
Co
Select OCP set resistor R=10.5k.
For NX2601, if one channel goes to hiccup current
limit, the other channels include LDO will go to hiccup
too.
Figure 20 - NX2601 LDO controller.
Typically, F O has to be higher than zero caused by
LDO Selection Guide
NX2601 offers a LDO controller. The selection of
ESR. FO is typically around several tens kHz to a few
MOSFET to meet LDO is more straight forward. The
hundred kHz. For this example, we select Fo=100kHz.
selection is that the Rdson of MOSFET should meet
gm is the forward trans-conductance of MOSFET.
For IRFR3706, gm=53.
the dropout requirement. For example.
VLDOIN =3.3V
Select Rf1=5kohm.
VLDOOUT =2.5V
Output capacitor is Sanyo POSCAP 4TPE150MI
ILoad =2A
The maximum Rdson of MOSFET should be
R RDSON = (VLDOIN − VLDOOUT ) × I LOAD
with 150uF, ESR=18mohm.
CC =
1
53 × 18mΩ
×
=155pF
2 × π × 100kHz × 5kΩ 1+53 × 18mΩ
= (3.3V − 2.5V) / 2A = 0.4Ω
Most of MOSFETs can meet the requirement. More
Rev. 2.3
12/01/06
Choose CC=150pF.
20
NX2601
For electrolytic or POSCAP, RC is typically
selected to be zero.
Rf2 is determined by the desired output voltage
R f 2 = R f 1 × VREF /(VLDOOUT − VREF )
= 5kΩ × 0.8V /(2.5V − 0.8) = 2.35kΩ
Choose Rf2=2.34kΩ.
Current Limit for LDO
Current limit of LDO is achieved by sensing the
as to the load as possible and plane connection is required.
4. Drain of the low-side MOSFET and source of
the high-side MOSFET need to be connected thru a plane
ans as close as possible. A snubber nedds to be placed
as close to this junction as possible.
5. Source of the lower MOSFET needs to be connected to the GND plane with multiple vias. One is not
enough. This is very important. The same applies to the
output capacitors and input capacitors.
LDO feedback voltage. When LDO_FB pin is below 0.4V,
6. Hdrv and Ldrv pins should be as close to
the IC goes into hiccup mode. The IC will turn off all the
MOSFET gate as possible. The gate traces should be
channel (Channel 1 and Channel 2 ) for 2096 cycles and
wide and short. A place for gate drv resistors is needed
start to restart system again.
to fine tune noise if needed.
7. Vcc capacitor, BST capacitor or any other by-
Layout Considerations
The layout is very important when designing high
frequency switching converters. Layout will affect noise
pickup and can cause a good design to perform with
less than expected results.
There are two sets of components considered in
the layout which are power components and small signal components. Power components usually consist of
input capacitors, high-side MOSFET, low-side MOSFET,
inductor and output capacitors. A noisy environment is
generated by the power components due to the switching power. Small signal components are connected to
sensitive pins or nodes. A multilayer layout which includes power plane, ground plane and signal plane is
recommended .
Layout guidelines:
1. First put all the power components in the top
layer connected by wide, copper filled areas. The input
passing capacitor needs to be placed first around the IC
and as close as possible. The capacitor on comp to
GND or comp back to FB needs to be place as close to
the pin as well as resistor divider.
8. The output sense line which is sensing output
back to the resistor divider should not go through high
frequency signals.
9. All GNDs need to go directly thru via to GND
plane.
10. The feedback part of the system should be
kept away from the inductor and other noise sources,
and be placed close to the IC.
11. In multilayer PCB, separate power ground and
analog ground. These two grounds must be connected
together on the PC board layout at a single point. The
goal is to localize the high current path to a separate
loop that does not interfere with the more sensitive analog control function.
capacitor, inductor, output capacitor and the MOSFETs
should be close to each other as possible. This helps to
reduce the EMI radiated by the power loop due to the
high switching currents through them.
2. Low ESR capacitor which can handle input RMS
ripple current and a high frequency decoupling ceramic
cap which usually is 1uF need to be practically touching the drain pin of the upper MOSFET, a plane connection is a must.
3. The output capacitors should be placed as close
Rev. 2.3
12/01/06
21
NX2601
TYPICAL APPLICATIONS
R11 10
+5V
11
REG FB
R13
1.65k
47pF
C16
10
2N3904
C24
C20
150uF
VOUT3
+2.5V/2A
M5
R15
C19
150uF
9
1uF
C18
0
150pF
R16
5k
R17
2.35k
R18
OFF R25 10k
ON
R26
10k
PVCC1
BST1
REG OUT
AUXVCC
HDRV1
SW1
7
LDRV1
R19
1.25k
R20
PGND1
6.8k
PVCC2
HDRV2
OFF
ON
R27 10k
6.8k
2N3904
R28
10k
VIN1
+12V
C4
0.1uF
25
M1
C3
100uF
L2 1.5uH
VOUT1
+1.2V@15A
26
R1 10.5k
C7
3 x (1500uF,19mohm)
R3
10k
22
M2
21
28
C5
R5
R4
20.8k
18
C8
1uF
68pF
+5V
17
C11
0.1uF
16
C9
180uF
M3
L4 1.5uH
ENSW2
SW2
R23
1.25k
LDRV2
6 RT
PGND2
VP
31 VREF
R6 3k
C14
2 x (1500uF,19mohm)
M4
19
20
Fb2 12
13
30
R10
C12
25k
4.7nF
Comp2
GND
4
VOUT2
+1.6V/10A
15
OCP2 14
R24 100k
C21 1nF
C2
180uF
24.8k
4.7nF
C22
BST2
2
L1 1uH
D2
R21
1.25k
R22
+5V
Fb1 29
Comp1
1 ENSW1
VIN1
C1
1uF
24
OCP1 27
LDO FB
ENLDO
23
D1
8 LDO OUT
3
1.5k
C25
1uF
2N3904
5
VCC
NX2601
VIN1
VIN2
+3.3V
C15
1uF
R12
5k
C17
68uF
C23
R8
10k
R9
10k
68pF
Figure 21 - NX2601 application with electrolytic capacitors as output capacitors
Rev. 2.3
12/01/06
22
NX2601
TYPICAL APPLICATIONS(cont')
R11 10
+5V
11
REG FB
R13
1.65k
10k
VIN1
C16
33pF
10
2N3904
9
VIN2
+3.3V
C24
C20
10uF
VOUT3
+2.5V/2A
M5
1uF
R15
2.5k
R16
5k
C19
47uF
C18
100pF
OFF R25 10k
1.5k
C25
1uF
2N3904
R26
10k
5
VCC
PVCC1
BST1
REG OUT
AUXVCC
HDRV1
SW1
7
LDO FB
LDRV1
ENLDO
R19
1.25k
PGND1
ON
R27 10k
6.8k
2N3904
R28
10k
PVCC2
BST2
M1
L2 0.68uH
26
R1 10.5k
R2
440
22
M2
21
C6
1.2nF
28
18
C5
R5
C8
1uF
VOUT1
+1.2V@10A
R3
11k
R4
22k
3.9nF
C22
C7
6 x 47uF
100pF
+5V
17
C11
0.1uF
16
C9
39uF
M3
L4 2.2uH
ENSW2
SW2
R23
1.25k
15
OCP2 14
LDRV2
6 RT
R24 30k
PGND2
VP
31 VREF
R6 3k
M4
19
20
Fb2 12
13
30
C21 1nF
C4
0.1uF
25
5k
HDRV2
OFF
VIN1
+12V
C3
100uF
C2
180uF
D2
R21
1.25k
2
L1 1uH
Fb1 29
Comp1
1 ENSW1
R22
+5V
24
OCP1 27
R20
6.8k
C1
1uF
8 LDO OUT
3
VIN1
23
D1
R17
2.35k
R18
ON
C15
1uF
R12
5k
R29
NX2601
C17
2.2uF
C6
1.2nF
R10
C12
Comp2
GND
4
R7
440
5k
C23
3.9nF
C14
2 x47uF
VOUT2
+1.8V/5A
R8
11k
R9
8.9k
100pF
Figure 22 - NX2601 application with ceramic capacitors as output capacitors
Rev. 2.3
12/01/06
23
NX2601
MLPQ 32 PIN 5 x 5 PACKAGE OUTLINE DIMENSIONS
D
D2
D/2
E/2
D2/2
E2/2
E
E2
e
L
R
2
1
Exposed Pad
N N-1
TOP VIEW
B
A
BTM VIEW
SEATING
PLANE
A1
A3
SIDE VIEW
SYMBOL
NAME
A
A1
A3
B
D
D2
E
E2
e
L
R
ND
NE
MIN
0.80
0.00
0.18
3.30
3.30
0.30
0.09
32 PIN 5 x 5
NOM
0.90
0.02
0.20REF
0.25
5.00BSC
3.45
5.00BSC
3.45
0.50BSC
0.40
--6
6
MAX
1.00
0.05
0.30
3.55
3.55
0.50
---
NOTE: ALL DIMENSIONS ARE DISPLAYED IN MILLIMETERS.
ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
Rev. 2.3
12/01/06
24
NX2601
MLPQ 32 PIN 5 x 5 TAPE AND REEL INFORMATION
NOTE:
1. R7 = 7 INCH LOCK REEL, R13 = 13 INCH LOCK REEL.
2. ALL DIMENSIONS ARE DISPLAYED IN MILLIMETERS.
Rev. 2.3
12/01/06
25