ADP1877 Reference Design
Reference Design
PRD 01135
FEATURES
Four Output Voltages: 1.2V, 1.8V, 3.3V, 5V
Output Current: 1A to 2.2A
Input Voltage: 10.8-13.2V
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 2 A,

VOUT2 = 1.8 V with a maximum output current of 1.8 A,

VOUT3 = 3.3 V with a maximum output current of 1 A,

VOUT4 = 5.0 V with a maximum output current of 2.2 A,
Design criteria are for simultaneous enable with coincidental tracking of VOUT1, VOUT2 and VOUT4 with VOUT3 for
turn on and enable 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 650 kHz for VOUT1 and VOUT2,
1000kHz for VOUT3 and VOUT4. The design is optimized for additional output capacitance on each rail to simulate
system usage and can be recompensated easily for changes in the output capacitance.
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. 1
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2009 Analog Devices, Inc. All rights reserved.
Reference Design
PRD 01135
TABLE OF CONTENTS
Features ......................................................................................................................................................................1
Description .................................................................................................................................................................1
ADP1877 ....................................................................................................................................................................1
Revision History .........................................................................................................................................................2
Schematic ...................................................................................................................................................................3
Notes...........................................................................................................................................................................8
Graphs ........................................................................................................................................................................9
Performance Data .....................................................................................................................................................14
TABLE OF FIGURES
Figure 1.
Figure 2.
Schematic: Vout1 and Vout2 (built on eval board 1) ..................................................................................3
Schematic: Vout3 and Vout4 (built on eval board 2) ..................................................................................4
Figure 3.
Schematic: Motherboard ........................................................................................................................5
Figure 4.
Vout1 (1.2V) Efficiency .........................................................................................................................9
Figure 5.
Vout2 (1.8V) Efficiency .........................................................................................................................9
Figure 6.
Vout3 (3.3V) Efficiency .......................................................................................................................10
Figure 7.
Figure 8.
Vout4 (5.0V) Efficiency .......................................................................................................................10
Enable Waveforms ............................................................................................................................... 11
Figure 9.
Disable Waveforms (full load) ............................................................................................................. 11
Figure 10.
Ripple Waveforms (full load) ..............................................................................................................12
Figure 11.
Vout1 and Vout2 Transient Response (50% step) ................................................................................12
Figure 12.
Vout3 and Vout4 Transient Response (50% step), Vin=12.0V ............................................................13
REVISION HISTORY
5/11/2007—Revision 1: Initial Version
8/14/2008—Revision 2: Provided Descriptions
4/22/2009—Revision 3: Changed to standard Windows fonts and sizes
Rev. 1 | Page 2 of 15
Reference Design
PRD 01135
SCHEMATIC
Figure 1.
Schematic: Vout1 and Vout2 (built on eval board 1)
Rf11
Rf12
PGOOD1
Rc1
Vin = 12V
Vout3 = 3.3V
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
EN
1
Vin = 12V
2
3
Cvin
RVcco
4
Cvcc
5
6
Cdr
Rfreq
7
EN
8
Vout3 = 3.3V
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
Vout2 = 1.8V
L2
17
TRK2 FB2 COMP2 RAMP2 SS2 PGOOD2 ILIM2 BST2
9
Vout1 = 1.2V
L1
23
CoV2
16
Cbst2
QH2
Rt21
Rr2
Css2
Vin = 12V
Cc22 Cc21
CiV2
Rt22
CIlim2
RIlim2
Rc2
PGOOD2
Rf22
Rf21
Note: Tracking resistors are on motherboard, not the eval board
Rev. 1 | Page 3 of 15
Reference Design
PRD 01135
Figure 2.
Schematic: Vout3 and Vout4 (built on eval board 2)
Rf11
Rf12
PGOOD1
Rc1
Vin = 12V
CIlim1
Cc12 Cc11
Rr1
Css1
RIlim1
32
31
30
29
28
27
26
25
Cbst1
CiV1
TRK1 FB1 COMP1 RAMP1 SS1 PGOOD1 ILIM1 BST1
EN
1
Vin = 12V
2
3
Cvin
RVcco
4
Cvcc
6
Cdr
Rfreq
EN
5
7
8
EN1
QH1
SW1
24
U1
SYNC
VIN
23
PGND1
ADP1877
VCCO
DL1
VDL
DL2
AGND
PGND2
FREQ
DH2
EN2
SW2
Rgcs1
CoV1
22
QL1
21
20
19
Rgcs2
QL2
18
10
11
12
13
Rr2
14
15
16
CoV2
Cbst2
Css2
QH2
Vin = 12V
Cc22 Cc21
CiV2
CIlim2
RIlim2
Rc2
PGOOD2
Rf22
Vout3 = 3.3V
L2
17
TRK2 FB2 COMP2 RAMP2 SS2 PGOOD2 ILIM2 BST2
9
Vout4 = 5V
L1
DH1
Rf21
Rev. 1 | Page 4 of 15
Reference Design
PRD 01135
Figure 3.
Schematic: Motherboard
Tracking resistors and enable jumpers are populated on the motherboard instead of the eval boards. Most of the
assumed extra output capacitance is also soldered on the motherboard.
Rev. 1 | Page 5 of 15
Reference Design
PRD 01135
Bill of Materials
Table 1.
Bill of Materials, Vout1 and Vout2 (1.2V and 1.8V) (Eval board 1)
Designator
Part Number
Manufacturer
U1
ADP1877
Analog Devices
40pin LFCSP
Dual Current Mode Controller
1
QH1
Si3446ADV
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
QH2
Si3446ADV
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
QL1
Si3446ADV
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
QL2
Si3446ADV
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
L1
DO1813H-222
Coilcraft
2.2uH
Unshielded Drum Core
Ferrite
1
L2
CoV1
DO1813H-222
JMK212BJ106MG-T
JMK212BJ106MG-T
JMK212BJ106MG-T
JMK212BJ106MG-T
Coilcraft
Taiyo Yuden
Taiyo Yuden
Taiyo Yuden
Taiyo Yuden
2.2uH
10uF
10uF
10uF
10uF
Unshielded Drum Core
0805
0805
0805
0805
Ferrite
MLCC / X5R / 6.3V
MLCC / X5R / 6.3V
MLCC / X5R / 6.3V
MLCC / X5R / 6.3V
1
3
1
2
15
CiV1
EMK212BJ106KG-T
Taiyo Yuden
10uF
0805
MLCC / X5R / 16V
1
CiV2
EMK212BJ106KG-T
Taiyo Yuden
10uF
0805
MLCC / X5R / 16V
1
Cvin
GRM21BR71C105K
Murata
1uF
0805
MLCC / X7R / 16V
1
Cbst1, Cbst2
Generic 10%
Vishay
100nF
0805
2
Css1
Generic 10%
Vishay
10nF
0805
Css2
Generic 10%
Vishay
10nF
0805
Boost Capacitor / COG or X7R
Soft Start Capacitor / COG or
X7R
Soft Start Capacitor / COG or
X7R
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
1.5nF
0603
Compensation Capacitor - CH1
1
Cc12
Generic 10%
Vishay
5pF
0603
Compensation Capacitor - CH1
1
Cc21
Generic 10%
Vishay
2.2nF
0603
Compensation Capacitor - CH2
1
Cc22
Generic 10%
Vishay
5pF
0603
Compensation Capacitor - CH2
1
RIlim1
Generic 1%
Vishay
3.32k
0603
Current Limit Resistor
1
RIlim2
Generic 1%
Vishay
2.74k
0603
Current Limit Resistor
1
Rgcs1
Generic 1%
Vishay
22k
0603
Current Sense Gain Set - 6V/V
1
Rgcs2
No Pop
Vishay
0603
1
Rfreq
Generic 5%
Vishay
97.6k
0603
Current Sense Gain Set - 12V/V
Frequency Set Resistor 650kHz
Rvcco
Generic 10%
Vishay
1 Ohm
0603
Decoupling Resistor
1
Rr1
Generic 10%
Vishay
249k
0603
Vout 1 Ramp Resistor
1
Rr2
Generic 10%
Vishay
432k
0603
Vout 2 Ramp Resistor
1
Rc1
Generic 10%
Vishay
16.9k
0603
Compensation Resistor
1
Rc2
Generic 10%
Vishay
71.5k
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
CoV2
Value
Package
Comment
Rev. 1 | Page 6 of 15
Quantity
1
1
1
Reference Design
Table 2.
PRD 01135
Bill of Materials, Vout3 and Vout4 (3.3V and 5.0V)
Designator
Part Number
U1
ADP1877
Manufacturer
Analog
Devices
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
1
QL2
NTGS3446G
ON-Semi
SOT23-6
Single 60mOhm 20V N-FET
1
L1
MSS1048-682
Coilcraft
6.8uH
Shielded Drum Core
Ferrite
1
L2
CoV1
MSS1048-682
JMK212BJ106MG-T
JMK212BJ106MG-T
6CE100KX
JMK212BJ106MG-T
GRM31CR60J107ME
GRM31CR60J226K
35CE10KX
Coilcraft
Taiyo Yuden
Taiyo Yuden
Sanyo
Taiyo Yuden
Murata
Murata
Sanyo
6.8uH
10uF
10uF
100uF
10uF
100uF
22uF
10uF
Shielded Drum Core
0805
0805
6.3x6mm SMT
0805
1206
1206
5x6mm SMT
Ferrite
MLCC / X5R / 6.3V
MLCC / X5R / 6.3V
Aluminum Electrolytic
MLCC / X5R / 6.3V
MLCC / X5R / 6.3V
MLCC / X5R / 6.3V
Aluminum Electrolytic
1
1
2
3
1
2
1
4
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
68pF
0603
Compensation Capacitor - CH1
1
Cc12
Generic 10%
Vishay
5pF
0603
Compensation Capacitor - CH1
1
Cc21
Generic 10%
Vishay
220pF
0603
Compensation Capacitor - CH2
1
Cc22
Generic 10%
Vishay
5pF
0603
Compensation Capacitor - CH2
1
RIlim1
Generic 1%
Vishay
3.32k
0603
Current Limit Resistor
1
RIlim2
Generic 1%
Vishay
3.01k
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
61.9k
0603
Frequency Set Resistor – 1MHz
1
Rvcco
Generic 10%
Vishay
1 Ohm
0603
Decoupling Resistor
1
Rr1
Generic 10%
Vishay
1.00M
0603
Vout 1 Ramp Resistor
1
Rr2
Generic 10%
Vishay
750k
0603
Vout 2 Ramp Resistor
1
Rc1
Generic 10%
Vishay
26.1k
0603
Compensation Resistor
1
Rc2
Generic 10%
Vishay
249k
0603
Compensation Resistor
1
Rf11
Generic 1%
Vishay
11.0k
0603
Feedback Resistor - CH1
1
Rf12
Generic 1%
Vishay
1.50k
0603
Feedback Resistor - CH1
1
Rf21
Generic 1%
Vishay
10k
0603
Feedback Resistor - CH2
1
Rf22
Generic 1%
Vishay
2.21k
0603
Feedback Resistor - CH2
1
CoV2
Value
Package
BOM items in bold are assumed additional system capacitance.
Rev. 1 | Page 7 of 15
Comment
Quantity
Reference Design
PRD 01135
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 in bold type in
the BOM.
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.
Except for the feedback resistors (Rfxx), E24 values may be substituted for the E96 values specified. The
feedback resistors need to be as specified.
Rev. 1 | Page 8 of 15
Reference Design
PRD 01135
GRAPHS
Figure 4.
Vout1 (1.2V) Efficiency
1.2V Efficiency
85.00%
80.00%
Efficiency
75.00%
70.00%
Vin max
Vin nom
Vin min
65.00%
60.00%
55.00%
50.00%
0
0.5
1
1.5
2
2.5
Current A
Figure 5.
Vout2 (1.8V) Efficiency
1.8V Efficiency
90.00%
85.00%
80.00%
Efficiency
75.00%
Vin max
70.00%
Vin nom
Vin min
65.00%
60.00%
55.00%
50.00%
0
0.2
0.4
0.6
0.8
1
1.2
Current
Rev. 1 | Page 9 of 15
1.4
1.6
1.8
2
Reference Design
PRD 01135
Figure 6.
Vout3 (3.3V) Efficiency
3.3V Efficiency
85.00%
80.00%
Efficiency
75.00%
70.00%
Vin max
Vin nom
Vin min
65.00%
60.00%
55.00%
50.00%
0
0.2
0.4
0.6
0.8
1
1.2
Current
Figure 7.
Vout4 (5.0V) Efficiency
5V Efficiency
95.00%
90.00%
85.00%
Efficiency
80.00%
Vin max
75.00%
Vin nom
70.00%
Vin min
65.00%
60.00%
55.00%
50.00%
0
0.5
1
1.5
Current (A)
Rev. 1 | Page 10 of 15
2
2.5
Reference Design
PRD 01135
Figure 8.
Figure 9.
Enable Waveforms
Disable Waveforms (full load)
Rev. 1 | Page 11 of 15
Reference Design
PRD 01135
Figure 10.
Figure 11.
Ripple Waveforms (full load)
Vout1 and Vout2 Transient Response (50% step)
Rev. 1 | Page 12 of 15
Reference Design
Figure 12.
PRD 01135
Vout3 and Vout4 Transient Response (50% step), Vin=12.0V
Note: At higher input voltages, depending on the load, the two channels of the 3.3V and 5V outputs may have
duty cycles that would require both outputs to switch simultaneously. The ADP1877 delays one of the outputs so
that it can measure the current in the low side fet during a quiet period. This causes some additional transient
response that resembles a beat frequency on the ripple. It is not instability and is well-bounded. It resembles
voltage drop in the ground plane due to the load change. Here is an example (50% step, Vin=13.2V). Note the
extra transition in the center, not due to the load transient.
Rev. 1 | Page 13 of 15
Reference Design
PRD 01135
PERFORMANCE DATA
Table 3.
Vout1/2 Temperature Rise over Ambient
Component
Vinnom
Units
U1
21.4
degC
L1
29.3
degC
QH1
19.4
degC
QL1
25.2
degC
L2
QH2
28.5
18.5
degC
degC
QL2
20.2
degC
Table 4.
Vout3/4 Temperature Rise over Ambient
Component
Vinnom
Units
U1
L1
25.5
19.8
degC
degC
QH1
28.3
degC
QL1
37.7
degC
L2
QH2
17.1
25.7
degC
degC
QL2
35.4
degC
Rev. 1 | Page 14 of 15
Reference Design
PRD 01135
©2009 Analog Devices, Inc. All rights reserved.
Trademarks and registered trademarks are the
property of their respective owners. Error! Unknown document property name.
Rev. 1 | Page 15 of 15