Preliminary Technical Data
ADP1877 Reference Design
FCDC 00186
FEATURES
Four Output Voltages: 1.2 V, 1.8 V, 3.3 V, 5 V
Output Current: 1 A to 3.5 A
Input voltage: 10.8-13.2 V
Ripple 50 mV ppk
Transient step ±5%, 50% max load
ADP1877 REFERENCE DESIGN DESCRIPTION
This ADP1877 Reference Design uses 10.8 V to 13.2 V for the input voltage. The output voltages and currents are as
follows:
•
VOUT1 = 1.2 V with a maximum output current of 3.5 A,
•
VOUT2 = 1.8 V with a maximum output current of 1.4 A,
•
VOUT3 = 3.3 V with a maximum output current of 2.1 A,
•
VOUT4 = 5.0 V with a maximum output current of 2.2 A,
Design criteria are for coincidental tracking of VOUT1, VOUT2 and VOUT3 with VOUT4 for both turn on and turn off. The ripple
and transient assumptions are 50 mV peak to peak voltage ripple and 5% deviation due to 50% instantaneous load step.
The switching frequency is fixed at 700 kHz for VOUT1 and VOUT2, 1000kHz for VOUT3 and VOUT4.
Rev. 0
Reference designs are as supplied “as is” and without warranties of any kind, express,
implied, or statutory including, but not limited to, any implied warranty of
merchantability or fitness for a particular purpose. No license is granted by implication or
otherwise under any patents or other intellectual property by application or use of
reference designs. Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Analog Devices reserves the right to change devices or specifications at any time without
notice. Trademarks and registered trademarks are the property of their respective
owners. Reference designs are not authorized to be used in life support devices or
systems.
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Fax: 781.461.3113
©2009 Analog Devices, Inc. All rights reserved.
Preliminary Technical Data
FCDC 00186
TABLE OF CONTENTS
Features....................................................................................................................................................................................................... 1
ADP1877 Reference Design Description .............................................................................................................................................. 1
Revision History........................................................................................................................................................................................ 2
General Description ................................................................................................................................................................................. 3
ADP1877................................................................................................................................................................................................ 3
Typical Performance Characteristics...................................................................................................................................................... 4
Schematic ................................................................................................................................................................................................. 10
TABLE OF FIGURES
Figure 1.
Calculated efficiency of 1.2V output ................................................................................................................................ 4
Figure 2.
Calculated efficiency of 1.8V output ................................................................................................................................ 4
Figure 3.
Calculated efficiency of 3.3V output ................................................................................................................................ 5
Figure 4.
Calculated efficiency of 5.0V output ................................................................................................................................ 5
Figure 5.
Calculated efficiency of 3.3V output with 2xSi2304BDS high and 2xSi2304BDS low.............................................. 6
Figure 6.
Calculated gain and phase of 1.8V output with additional 15x10uF ceramic ............................................................ 6
Figure 7.
Calculated gain and phase of 3.3V output with additional 40uF of aluminum electrolytic and 225uF of ceramic
7
Figure 8.
Calculated gain and phase of 5.0V output with additional 300uF of aluminum electrolytic and 2x10uF ceramic
7
Figure 9.
Calculated ripple and transient of 1.2V output with additional 10uF ceramic .......................................................... 8
Figure 10.
Calculated ripple and transient of 1.8V output with additional 15x10uF ceramic ............................................... 8
Figure 11.
ceramic
Calculated ripple and transient of 3.3V output with additional 40uF of aluminum electrolytic and 225uF of
9
Figure 12.
ceramic
Calculated ripple and transient of 5.0V output with additional 300uF of aluminum electrolytic and 2x10uF
9
Figure 13.
Schematic: VOUT1 and VOUT2 ......................................................................................................................................... 10
Figure 14.
Schematic: VOUT3 ,VOUT4 ................................................................................................................................................ 11
REVISION HISTORY
2/12/2009—Revision 0: Initial Version
Rev. 0 | Page 2 of 14
Preliminary Technical Data
FCDC 00186
GENERAL DESCRIPTION
ADP1877
The ADP1877 is a current mode dual-phase step-down switching controller with integrated drivers that drive Nchannel
synchronous power MOSFETs. The two PWM outputs are phase shifted 180º, which reduces the input RMS current
thus minimizing required input capacitance.
The boost diodes are built into the ADP1877, thus lowering the overall system cost and component count. The ADP1877
can be set to operate in pulse skip high efficiency mode under light load or in forced PWM (continuous conduction mode).
The ADP1877 includes programmable soft start, output overvoltage protection, programmable current limit, power good,
tracking function, and programmable oscillator frequency that ranges from 200 kHz to 1.5 MHz. The ADP1877 provides
an output voltage accuracy of ±1% over temperature, superior transient response and reduced output capacitance. This
part can be powered from a 2.75V to 15V supply and is available in 32 pin LFCSP package.
Rev. 0 | Page 3 of 14
Preliminary Technical Data
FCDC 00186
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 1.
Calculated efficiency of 1.2V output
Efficiency and Loss
100%
1.200
95%
1.000
90%
0.800
80%
Watt Loss
Pout/Pin
85%
75%
0.600
70%
0.400
65%
Vin=10.8, Eff
60%
Vin=13.2, Eff
55%
0.200
Vin=10.8, Loss
Vin=13.2, Loss
50%
0.001
0.501
1.001
1.501
2.001
Iout Amp
Figure 2.
2.501
3.001
3.501
Calculated efficiency of 1.8V output
Efficiency and Loss
100%
0.000
4.001
0.600
95%
0.500
90%
0.400
80%
Watt Loss
Pout/Pin
85%
75%
0.300
70%
0.200
65%
Vin=10.8, Eff
60%
Vin=13.2, Eff
55%
0.100
Vin=10.8, Loss
Vin=13.2, Loss
50%
0.001
0.201
0.401
0.601
0.801
Iout Amp
1.001
Rev. 0 | Page 4 of 14
1.201
1.401
0.000
1.601
Preliminary Technical Data
FCDC 00186
Figure 3.
Calculated efficiency of 3.3V output
Efficiency and Loss
100%
0.800
95%
0.700
90%
0.600
0.500
80%
Watt Loss
Pout/Pin
85%
75%
0.400
70%
0.300
65%
Vin=10.8, Eff
60%
Vin=13.2, Eff
55%
Vin=10.8, Loss
0.200
0.100
Vin=13.2, Loss
50%
0.001
0.501
1.001
1.501
Iout Amp
Figure 4.
2.001
Calculated efficiency of 5.0V output
Efficiency and Loss
100%
0.900
95%
0.800
90%
0.700
85%
0.600
80%
Watt Loss
Pout/Pin
0.000
2.501
0.500
75%
0.400
70%
0.300
65%
Vin=10.8, Eff
60%
0.200
Vin=13.2, Eff
55%
Vin=10.8, Loss
0.100
Vin=13.2, Loss
50%
0.001
0.501
1.001
1.501
Iout Amp
Rev. 0 | Page 5 of 14
2.001
0.000
2.501
Preliminary Technical Data
Figure 5.
FCDC 00186
Calculated efficiency of 3.3V output with 2xSi2304BDS high and 2xSi2304BDS low
94.32962k 94.39125k
-61.63115
Y2
Y1
80
150
60
0
-20
Phase / degrees
Gain / dB
20
53.212466
100
40
-40
50
53.205817
0
-6.64850m
-50
-100
-60
-150
-80
100
200
400
1k
2k
4k
10k
20k
40k
100k 200k 400k
REF
A
1M
freq / Hertz
Figure 6.
Calculated gain and phase of 1.8V output with additional 15x10uF ceramic
86.61444k 86.66495k
50.506033
Y2
Y1
80
150
60
100
Gain / dB
20
0
-20
-40
Phase / degrees
40
55.473242
50
-55.47171
1.535427m
0
-50
-100
-60
-150
-80
100
200
400
1k
2k
4k
10k
20k
freq / Hertz
Rev. 0 | Page 6 of 14
40k
100k 200k 400k
REF
A
1M
Preliminary Technical Data
Figure 7.
FCDC 00186
Calculated gain and phase of 3.3V output with additional 40uF of aluminum electrolytic and 225uF of ceramic
52.25816k 52.25816k
0.0000000
Y2
Y1
80
150
60
100
40
Gain / dB
0
-20
Phase / degrees
66.439383
20
-40
50
-66.44201
-2.62744m
0
-50
-100
-60
-150
-80
100
200
400
1k
2k
4k
10k
20k
40k
100k 200k 400k
REF
A
1M
freq / Hertz
Figure 8.
Calculated gain and phase of 5.0V output with additional 300uF of aluminum electrolytic and 2x10uF ceramic
82.27057k 82.35031k
-79.73484
Y2
Y1
80
150
60
100
40
Gain / dB
20
0
-20
-40
Phase / degrees
66.670822
50
66.667860
2.962289m
0
-50
-100
-60
-150
-80
100
200
400
1k
2k
4k
10k
20k
freq / Hertz
Rev. 0 | Page 7 of 14
40k
100k 200k 400k
REF
A
1M
Preliminary Technical Data
Figure 9.
FCDC 00186
Calculated ripple and transient of 1.2V output with additional 10uF ceramic
1.24
Vout / V
1.22
1.2
1.18
1.16
1.14
0
20
40
60
80
100
120
140
160
time/uSecs
180
20uSecs/div
Figure 10. Calculated ripple and transient of 1.8V output with additional 15x10uF ceramic
1.81
Vout / V
1.805
1.8
1.795
1.79
1.785
0
20
40
60
80
100
time/uSecs
120
140
160
180
20uSecs/div
Rev. 0 | Page 8 of 14
Preliminary Technical Data
FCDC 00186
Figure 11. Calculated ripple and transient of 3.3V output with additional 40uF of aluminum electrolytic and 225uF of ceramic
3.315
Vout / V
3.31
3.305
3.3
3.295
3.29
0
20
40
60
80
100
120
140
160
time/uSecs
180
20uSecs/div
Figure 12. Calculated ripple and transient of 5.0V output with additional 300uF of aluminum electrolytic and 2x10uF ceramic
5.08
5.06
5.04
Vout / V
5.02
5
4.98
4.96
4.94
4.92
4.9
0
20
40
60
80
100
time/uSecs
120
140
160
180
20uSecs/div
Rev. 0 | Page 9 of 14
Preliminary Technical Data
FCDC 00186
SCHEMATIC
Figure 13. Schematic: VOUT1 and VOUT2
Rf11
Rf12
PGOOD1
Rc1
Vin = 12V
Vout4 = 5V
CIlim1
Rt11
Cc12 Cc11
Rr1
Css1
RIlim1
Rt12
32
31
30
29
28
27
26
25
Cbst1
CiV1
TRK1 FB1 COMP1 RAMP1 SS1 PGOOD1 ILIM1 BST1
1
Vin = 12V
2
3
Cvin
RVcco
4
Cvcc
5
6
Cdr
Rfreq
7
8
Vout4 = 5V
EN1
SW1
U1
SYNC
DH1
VIN
PGND1
ADP1877
VCCO
DL1
VDL
DL2
AGND
PGND2
FREQ
DH2
EN2
SW2
QH1
24
Rgcs1
CoV1
22
QL1
21
20
19
Rgcs2
QL2
18
10
11
12
13
14
15
16
Vout2 = 1.8V
L2
17
TRK2 FB2 COMP2 RAMP2 SS2 PGOOD2 ILIM2 BST2
9
Vout1 = 1.2V
L1
23
CoV2
Cbst2
QH2
Rt21
Rr2
Css2
Vin = 12V
Cc22 Cc21
CiV2
Rt22
CIlim2
Rc2
PGOOD2
Rf22
Rf21
Rev. 0 | Page 10 of 14
RIlim2
Preliminary Technical Data
FCDC 00186
Figure 14. Schematic: VOUT3 ,VOUT4
Rf11
Rf12
PGOOD1
Rc1
Vin = 12V
CIlim1
Cc12 Cc11
Rr1
Css1
RIlim1
32
Ren1
1
Vin = 12V
2
Ren2
3
Cvin
31
30
29
28
27
26
25
Cbst1
CiV1
TRK1 FB1 COMP1 RAMP1 SS1 PGOOD1 ILIM1 BST1
RVcco
4
Cvcc
5
6
Cdr
Rfreq
7
8
Vout4 = 5V
EN1
SW1
U1
SYNC
DH1
VIN
PGND1
ADP1877
VCCO
DL1
VDL
DL2
AGND
PGND2
FREQ
DH2
EN2
SW2
QH1
24
Rgcs1
CoV1
22
QL1
21
20
19
Rgcs2
QL2
18
10
11
12
13
14
15
16
Vout3 = 3.3V
L2
17
TRK2 FB2 COMP2 RAMP2 SS2 PGOOD2 ILIM2 BST2
9
Vout4 = 5V
L1
23
CoV2
Cbst2
QH2
Rt21
Rr2
Css2
Vin = 12V
Cc22 Cc21
CiV2
Rt22
CIlim2
Rc2
PGOOD2
Rf22
Rf21
Rev. 0 | Page 11 of 14
RIlim2
Preliminary Technical Data
FCDC 00186
Bill of Materials
Table 1. Vout1, and Vout2 Bill of Materials (1.2 V and 1.8 V)
Designator
Part Number
U1
ADP1877
Manufacturer
Analog
Devices
Value
Package
Comment
Quantity
40pin LFCSP
Dual Current Mode Controller
1
QH1
NTGS3446G
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
QH2
NTGS3446G
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
QL1
NTGS3446G
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
2
QL2
NTGS3446G
ON-Semi
Single 60mOhm 20V N-FET
1
L1
DO1813H-122
Coilcraft
1.15uH
SOT23-6
Unshielded Drum
Core
Ferrite
1
L2
LPS5030-822
Coilcraft
8.2uH
Shielded Drum Core
Ferrite
1
CoV1
JMK212BJ226MG-T
Taiyo Yuden
22uF
0805
MLCC / X5R / 6.3V
2
CoV2
JMK212BJ106MG-T
Taiyo Yuden
10uF
0805
MLCC / X5R / 6.3V
1
CiV1
EMK212BJ106KG-T
Taiyo Yuden
10uF
0805
MLCC / X5R / 16V
1
CiV2
EMK212BJ106KG-T
Taiyo Yuden
10uF
0805
MLCC / X5R / 16V
1
Cvin
Cbst1,
Cbst2
GRM21BR71C105K
Murata
1uF
0805
MLCC / X7R / 16V
1
Generic 10%
Vishay
100nF
0805
Boost Capacitor / COG or X7R
2
Css1
Generic 10%
Vishay
10nF
0805
Soft Start Capacitor / COG or X7R
1
Css2
Generic 10%
Vishay
10nF
0805
Soft Start Capacitor / COG or X7R
1
CIlim1
Generic 10%
Vishay
33pF
0805
Current Limit Capacitor
1
CIlim2
Generic 10%
Vishay
33pF
0805
Current Limit Capacitor
1
Cdr
GRM185R60J105KE21
Murata
1uF
0603
MLCC / X5R / 6.3V
1
Cvcc
GRM185R60J105KE21
Murata
1uF
0603
MLCC / X5R / 6.3V
1
Cc11
Generic 10%
Vishay
470pF
0603
Compensation Capacitor - CH1
1
Cc12
Generic 10%
Vishay
5pF
0603
Compensation Capacitor - CH1
1
Cc21
Generic 10%
Vishay
68pF
0603
Compensation Capacitor - CH2
1
Cc22
Generic 10%
Vishay
5pF
0603
Compensation Capacitor - CH2
1
RIlim1
Generic 1%
Vishay
2.4k
0603
Current Limit Resistor
1
RIlim2
Generic 1%
Vishay
2.2k
0603
Current Limit Resistor
1
Rgcs1
Generic 1%
Vishay
22k
0603
Current Sense Gain Set - 6V/V
1
Rgcs2
No Pop
Vishay
0603
Current Sense Gain Set - 12V/V
1
Rfreq
Generic 5%
Vishay
82k
0603
Frequency Set Resistor - 700kHz
1
Rvcco
Generic 10%
Vishay
1 Ohms
0603
Decoupling Resistor
1
Rr1
Generic 10%
Vishay
240k
0603
Vout 1 Ramp Resistor
1
Rr2
Generic 10%
Vishay
430k
0603
Vout 2 Ramp Resistor
1
Rc1
Generic 10%
Vishay
20k
0603
Compensation Resistor
1
Rc2
Generic 10%
Vishay
240k
0603
Compensation Resistor
1
Rf11
Generic 1%
Vishay
10k
0603
Feedback Resistor - CH1
1
Rf12
Generic 1%
Vishay
10k
0603
Feedback Resistor - CH1
1
Rf21
Generic 1%
Vishay
20k
0603
Feedback Resistor - CH2
1
Rf22
Generic 1%
Vishay
10k
0603
Feedback Resistor - CH2
1
Rt11
Generic 1%
Vishay
10k
0603
Voltage track Resistor - CH1
1
Rt12
Generic 1%
Vishay
10k
0603
Voltage track Resistor - CH1
1
Rt21
Generic 1%
Vishay
20k
0603
Voltage track Resistor - CH2
1
Rt22
Generic 1%
Vishay
10k
0603
Voltage track Resistor - CH2
1
Rev. 0 | Page 12 of 14
Preliminary Technical Data
FCDC 00186
Vout3 and Vout4 Bill of Materials (3.3 V and 5.0 V)
Designator
Part Number
U1
ADP1877
Manufacturer
Analog
Devices
QH1
NTGS3446G
QH2
NTGS3446G
QL1
NTGS3446G
Value
Package
Comment
Quantity
40pin LFCSP
Dual Current Mode Controller
1
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
QL2
NTGS3446G
ON-Semi
Single 60mOhm 20V N-FET
1
L1
MSS1048-682
Coilcraft
6.8uH
Shielded Drum Core
SOT23-6
Ferrite
1
Ferrite
1
MLCC / X5R / 6.3V
1
L2
MSS1048-682
Coilcraft
6.8uH
Shielded Drum Core
CoV1
JMK212BJ106MG-T
Taiyo Yuden
10uF
0805
CoV2
JMK212BJ106MG-T
Taiyo Yuden
10uF
0805
MLCC / X5R / 6.3V
1
CiV1
EMK212BJ106KG-T
Taiyo Yuden
10uF
0805
MLCC / X5R / 16V
1
CiV2
EMK212BJ106KG-T
Taiyo Yuden
10uF
0805
MLCC / X5R / 16V
1
Cvin
Cbst1,
Cbst2
GRM21BR71C105K
Murata
1uF
0805
MLCC / X7R / 16V
1
Generic 10%
Vishay
100nF
0805
Boost Capacitor / COG or X7R
2
Css1
Generic 10%
Vishay
100nF
0805
Soft Start Capacitor / COG or X7R
1
Css2
Generic 10%
Vishay
10nF
0805
Soft Start Capacitor / COG or X7R
1
CIlim1
Generic 10%
Vishay
33pF
0805
Current Limit Capacitor
1
CIlim2
Generic 10%
Vishay
33pF
0805
Current Limit Capacitor
1
Cdr
GRM185R60J105KE21
Murata
1uF
0603
MLCC / X5R / 6.3V
1
Cvcc
GRM185R60J105KE21
Murata
1uF
0603
MLCC / X5R / 6.3V
1
Cc11
Generic 10%
Vishay
33pF
0603
Compensation Capacitor - CH1
1
Cc12
Generic 10%
Vishay
5pF
0603
Compensation Capacitor - CH1
1
Cc21
Generic 10%
Vishay
68pF
0603
Compensation Capacitor - CH2
1
Cc22
Generic 10%
Vishay
5pF
0603
Compensation Capacitor - CH2
1
RIlim1
Generic 1%
Vishay
3.3k
0603
Current Limit Resistor
1
RIlim2
Generic 1%
Vishay
3.0k
0603
Current Limit Resistor
1
Rgcs1
Generic 1%
Vishay
22k
0603
Current Sense Gain Set - 6V/V
1
Rgcs2
Generic 1%
Vishay
22k
0603
Current Sense Gain Set - 6V/V
1
Rfreq
Generic 5%
Vishay
51k
0603
Frequency Set Resistor - 700kHz
1
Rvcco
Generic 10%
Vishay
1 Ohms
0603
Decoupling Resistor
1
Rr1
Generic 10%
Vishay
750k
0603
Vout 1 Ramp Resistor
1
Rr2
Generic 10%
Vishay
750k
0603
Vout 2 Ramp Resistor
1
Rc1
Generic 10%
Vishay
51k
0603
Compensation Resistor
1
Rc2
Generic 10%
Vishay
240k
0603
Compensation Resistor
1
Rf11
Generic 1%
Vishay
11k
0603
Feedback Resistor - CH1
1
Rf12
Generic 1%
Vishay
1.5k
0603
Feedback Resistor - CH1
1
Rf21
Generic 1%
Vishay
10k
0603
Feedback Resistor - CH2
1
Rf22
Generic 1%
Vishay
2.2k
0603
Feedback Resistor - CH2
1
Rt11
Generic 1%
Vishay
10k
0603
Voltage track Resistor - CH1
1
1
Rt12
Generic 1%
Vishay
10k
0603
Voltage track Resistor - CH1
Ren1
Generic 1%
Vishay
150k
0603
Voltage track Resistor - CH2
1
Ren2
Generic 1%
Vishay
10k
0603
Voltage track Resistor - CH2
1
Rev. 0 | Page 13 of 14
Preliminary Technical Data
FCDC 00186
NOTES
Reference designators shown on the schematic but not listed on the Bill of Materials are place holders for possible design
adjustments (snubbers, additional decoupling capacitors and clamp diodes). These components should be put in the
layout, but not populated unless after testing it is deemed necessary.
If a different number, or different type of output capacitors are used on the switching outputs the loop compensation
components may need adjustment. The assumed additional output caps are listed on the transient and bode plot figures.
Efficiency calculations are estimates and are not verified in actual hardware.
FETs and other components with quantities greater than 1 are connected in parallel with the other FETs / components of
the same reference designator. Paralleled FETs should be placed physically close together and have large power planes
connecting all the drains together and large power planes connecting all the sources together. Gate drive resistors may be
used if there is concern about possible paralleling issues.
Ground symbols with multiple parallel lines (not the triangle symbol) designator should be connected together with one
small plane and tied to the power ground plane (triangle symbol) at one point near the IC. Each IC should have its own
signal ground pour. The PGND1 and PGND2 pins should be connected directly to the source of the lowside MOSFET for
that channel with short wide traces. They should not connect into the main ground plane except at the MOSFET sources.
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