MAXIM MAX1864, MAX1865 User Manual
General Description
The MAX1864/MAX1865 power-supply controllers are
designed to address cost-conscious applications such
as cable modem Consumer Premise Equipment (CPE),
xDSL CPE, and set-top boxes. Operating off a low-cost,
unregulated DC supply (such as a wall adapter output),
the MAX1864 generates three positive outputs, and the
MAX1865 generates four positive outputs and one negative output to provide a cost-effective system power
supply.
The MAX1864 includes a current-mode synchronous
step-down controller and two positive regulator gain
blocks. The MAX1865 has one additional positive gain
block and one negative regulator gain block. The main
synchronous step-down controller generates a
high-current output that is preset to 3.3V or adjustable
from 1.236V to 0.8 ✕ VINwith an external resistivedivider. The 100kHz/200kHz operating frequency
allows the use of low-cost aluminum-electrolytic capacitors and low-cost power magnetics. Additionally, the
MAX1864/MAX1865 step-down controllers sense the
voltage across the low-side MOSFET’s on-resistance to
efficiently provide the current-limit signal, eliminating
the need for costly current-sense resistors.
The MAX1864/MAX1865 generate additional supply
rails at low cost. The positive regulator gain blocks use
an external PNP pass transistor to generate low-voltage
rails directly from the main step-down converter (such
as 2.5V or 1.8V from the main 3.3V output) or higher
voltages using coupled windings from the step-down
converter (such as 5V, 12V, or 15V). The MAX1865’s
negative gain block uses an external NPN pass transistor in conjunction with a coupled winding to generate
-5V, -12V, or -15V.
All output voltages are externally adjustable, providing
maximum flexibility. Additionally, the MAX1864/
MAX1865 feature soft-start for the step-down converter
and all the positive linear regulators, and have a powergood output that monitors all of the output voltages.
Applications
xDSL, Cable, and ISDN Modems
Set-Top Boxes
Wireless Local Loop
Features
♦ 4.5V to 28V Input Voltage Range
♦ Master DC-DC Step-Down Converter
Preset 3.3V or Adjustable (1.236V to 0.8 ✕ VIN)
Output Voltage
Fixed-Frequency (100kHz/200kHz) PWM
Controller
No Current-Sense Resistor
Adjustable Current Limit
95% Efficient
♦ Two (MAX1864)/Four (MAX1865) Analog
Gain Blocks
Positive Analog Blocks Drive Low-Cost PNP
Pass Transistors to Build Positive Linear
Regulators
Negative Analog Block (MAX1865) Drives a
Low-Cost NPN Pass Transistor to Build a
Negative Linear Regulator
♦ Power-Good Indicator
♦ Soft-Start Ramp for All Positive Regulators
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
________________________________________________________________ Maxim Integrated Products 1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
POK IN
VL
BST
DH
LX
DL
GND
ILIM
TOP VIEW
MAX1864
16 QSOP
COMP
OUT
FB2
FB
B2
B3
FB3
Pin Configurations
Ordering Information
19-2030; Rev 0; 4/01
EVALUATION KIT
AVAILABLE
PART
TEMP.
RANGE
PIN-
f
OSC
(kHz)
MAX1864TEEE
16 QSOP 200
MAX1864UEEE
16 QSOP 100
MAX1865TEEP
20 QSOP 200
MAX1865UEEP
20 QSOP 100
Pin Configurations continued at end of data sheet.
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PACKAGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= 12V, ILIM = FB = GND, V
BST
- VLX= 5V, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN, B2, B3, B4 to GND............................................-0.3V to +30V
B5 to OUT...............................................................-20V to +0.3V
VL, POK, FB, FB2, FB3, FB4, FB5 to GND ...............-0.3V to +6V
LX to BST..................................................................-6V to +0.3V
BST to GND ............................................................-0.3V to +36V
DH to LX....................................................-0.3V to (V
BST
+ 0.3V)
DL, OUT, COMP, ILIM to GND......................-0.3V to (V
L
+ 0.3V)
VL Output Current ...............................................................50mA
VL Short Circuit to GND...................................................≤100ms
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........666mW
20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GENERAL
Operating Input Voltage Range
(Note 1)
V
IN
4.5 28 V
MAX1864 1.0 2
Quiescent Supply Current I
IN
VFB = 0, V
OUT
= 4V,
V
FB2
= V
FB3
= V
FB4
= 1.5V,
V
FB5
= -0.1V
MAX1865 1.4 3
mA
VL REGULATOR
Output Voltage VL 6V < VIN < 28V, 0.1mA < I
LOAD
< 20mA
V
Power-Supply Rejection PSRR VIN = 6V to 28V 3 %
Undervoltage Lockout Trip Level
VL rising, 3% hysteresis (typ) 3.2 3.5 3.8 V
Minimum Bypass Capacitance
)
10mΩ < ESR < 500mΩ 1µF
DC-DC CONTROLLER
Output Voltage (Preset Mode) V
OUT
FB = GND
V
Typical Output Voltage Range
(Adjustable Mode) (Note 2)
V
OUT
V
FB Set Voltage
(Adjustable Mode)
V
SET
FB = COMP
V
FB Dual Mode™ Threshold 50
mV
FB Input Leakage Current I
FB
VFB = 1.5V
nA
FB to COMP Transconductance g
m
FB = COMP, I
COMP
= ±5µA 70
µS
Current-Sense Amplifier Voltage
Gain
A
LIM
VIN - VLX = 250mV
4.9
V/V
Current-Limit Threshold
(Internal Mode)
V
ILIM
= 5.0V
mV
Current-Limit Threshold
(External Mode)
V
ILIM
= 2.5V
mV
Dual Mode is a trademark of Maxim Integrated Products, Inc.
V
UVLO
C
BYP(MIN
V
VALLEY
V
VALLEY
4.75 5.00 5.25
3.272 3.314 3.355
1.236 0.8 x V
1.221 1.236 1.252
4.46
190 250 310
440 530 620
100 150
0.01 100
100 140
IN
5.44
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
_______________________________________________________________________________________ 3
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX186_T
Switching Frequency f
OSC
MAX186_U 80
kHz
Maximum Duty Cycle D
MAX
77 82 90 %
Soft-Start Period t
SOFT
1/f
OSC
Soft-Start Steps
V
DH Output Low Voltage I
SINK
= 10mA, measured from DH to LX 0.1 V
DH Output High Voltage
0.1 V
DL Output Low Voltage I
SINK
= 10mA, measured from DL to GND 0.1 V
DL Output High Voltage
V
DH, DL On-Resistance 310Ω
Output Drive Current Sourcing or sinking, VDH or VDL = VL/2 0.5 A
LX, BST Leakage Current V
BST
= VLX = VIN = 28V, VFB = 1.5V
20 µA
POSITIVE ANALOG GAIN BLOCKS
FB2, FB3, FB4 Regulation
Voltage
VB2 = VB3 = VB4 = 5V,
I
B2
= IB3 = IB4 = 1mA (sink)
V
FB2, FB3, FB4 to B_
Transconductance
ΔV
FB
_
V
B2
= VB3 = VB4 = 5V, IB2 = IB3 = IB4 =
0.5mA to 5mA (sink)
-1
%
Feedback Input Leakage
Current
I
FB
_V
FB2
= V
FB3
= V
FB4
= 1.5V
nA
10 23
Driver Sink Current IB_
V
FB2
= V
FB3
=
V
FB4
= 1.188V
26
mA
NEGATIVE ANALOG GAIN BLOCK
FB5 Regulation Voltage
V
B5
= V
OUT
- 2V, V
OUT
= 3.5V, IB5 = 1mA
(source)
-20 -5
mV
FB5 to B5 Transconductance ΔV
FB5
VB5 = 0, IB5 = 0.5mA to 5mA (source) -13
mV
Feedback Input Leakage
Current
I
FB5
V
FB5
= -100mV
nA
Driver Source Current I
B5
V
FB5
= 200mV, VB5 = V
OUT
- 2.0V, V
OUT
=
3.5V
10 25 mA
POWER GOOD (POK)
OUT Trip Level (Preset Mode)
3
V
FB Trip Level (Adjustable Mode)
Falling edge, 1% hysteresis (typ)
V
FB2, FB3, FB4 Trip Level Falling edge, 1% hysteresis (typ)
V
FB5 Trip Level Rising edge, 35mV hysteresis (typ)
mV
POK Output Low Level I
SINK
= 1mA 0.4 V
POK Output High Leakage V
POK
= 5V 1 µA
THERMAL PROTECTION (Note 3)
Thermal Shutdown Rising temperature
°C
Thermal Shutdown Hysteresis 15 °C
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 12V, ILIM = FB = GND, V
BST
- VLX= 5V, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)
160 200 240
I
I
FB = GND, falling edge, 1% hysteresis (typ) 2.88
= 10mA, measured from BST to DH
SOURCE
= 10mA, measured from DL to GND VL - 0.1
SOURCE
VB2 = VB3 = VB4 = 2.5V
VB2 = VB3 = VB4 = 4.0V
1.226 1.240 1.257
1.070 1.114 1.159
1.070 1.114 1.159
368 500 632
100 120
1024
V
/64
REF
0.03
0.01 100
0.01 100
160
-1.75
+10
-20
3.12
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
4 _______________________________________________________________________________________
PARAMETER
CONDITIONS
GENERAL
Operating Input Voltage Range
(Note 1)
V
IN
4.5 28 V
MAX1864 2
Quiescent Supply Current I
IN
VFB = 0, V
OUT
= 4V, V
FB2
= V
FB3
= V
FB4
= 1.5V,
V
FB5
= -0.1V
MAX1865 3
mA
VL REGULATOR
Output Voltage VL 6V < VIN < 28V, 0.1mA < I
LOAD
<20mA
V
Power-Supply Rejection PSRR VIN = 6V to 28V 3 %
Undervoltage Lockout Trip Level
VL rising, 3% hysteresis (typ) 3 4 V
DC-DC CONTROLLER
Output Voltage (Preset Mode) V
OUT
FB = GND
V
Feedback Set Voltage
(Adjustable Mode)
V
SET
FB = COMP
V
Current-Sense Amplifier Voltage
Gain
A
LIM
VIN - VLX = 250mV
V/V
Current-Limit Threshold
(Internal Mode)
V
ILIM
= 5V
mV
Current-Limit Threshold
(External Mode)
V
ILIM
= 2.5V
mV
MAX186_T
Switching Frequency f
OSC
MAX186_U 80
Maximum Duty Cycle D
MAX
74 90 %
POSITIVE ANALOG GAIN BLOCKS
FB2, FB3, FB4 Regulation
Voltage
VB2 = VB3 = VB4 = 5V, IB2 = IB3 = IB4 =
1mA (sink)
V
FB2, FB3, FB4 to B_
Transconductance
VB2 = VB3 = VB4 = 5V, IB2 = IB3 = IB4 =
0.5mA to 5mA (sink)
%
NEGATIVE ANALOG GAIN BLOCK
FB5 Regulation Voltage
V
B5
= V
OUT
- 2V, V
OUT
= 3.5V, IB5 = 1mA
(source)
-25
mV
FB5 to B5 Transconductance
VB5 = 0, IB5 = 0.5mA to 5mA (source)
mV
ELECTRICAL CHARACTERISTICS
(VIN= 12V, ILIM = FB = GND, V
BST
- VLX= 5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 4)
SYMBOL
V
UVLO
MIN MAX UNITS
4.75 5.25
3.247 3.380
V
VALLEY
V
VALLEY
ΔVFB_
ΔV
FB5
1.211 1.261
4.12 5.68
150 350
400 660
160 240
1.215 1.265
120
-2.25
+10
-30
kHz
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
_______________________________________________________________________________________ 5
Note 1: Connect VL to IN for operation with VIN< 5V.
Note 2: See Output Voltage Selection section.
Note 3: The internal 5V linear regulator (VL) powers the thermal shutdown block. Shorting VL to GND disables thermal shutdown.
Note 4: Specifications to -40°C are guaranteed by design, not production tested.
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 12V, ILIM = FB = GND, V
BST
- VLX= 5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 4)
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
POWER GOOD (POK)
OUT Trip Level (Preset Mode)
V
FB Trip Level
(Adjustable Mode)
Falling edge, 1% hysteresis (typ)
V
FB2, FB3, FB4 Trip Level Falling edge, 1% hysteresis (typ)
V
FB5 Trip Level Rising edge, 35mV hysteresis (typ)
mV
50
0.01 1010.1
EFFICIENCY vs. LOAD CURRENT
(PRESET MODE)
100
70
60
90
80
MAX1864/65 toc01
LOAD CURRENT (A)
EFFICIENCY (%)
VIN = 6.5V
VIN = 8V
VIN = 12V
VIN = 18V
VIN = 24V
V
OUT
= 3.3V
3.27
3.29
3.28
3.31
3.30
3.32
3.33
0 1.0 1.50.5 2.0 2.5 3.0
OUTPUT VOLTAGE vs. LOAD CURRENT
(PRESET MODE)
MAX1864/65 toc02
LOAD CURRENT (A)
OUTPUT VOLTAGE (V)
50
0.01 1010.1
EFFICIENCY vs. LOAD CURRENT
(ADJUSTABLE MODE)
100
70
60
90
80
MAX1864/65 toc03
LOAD CURRENT (A)
EFFICIENCY (%)
VIN = 6.5V
VIN = 8V
VIN = 12V
VIN = 18V
VIN = 24V
V
OUT
= 5.0V
Typical Operating Characteristics
(Circuit of Figure 1, VIN= 12V, V
OUT
= 3.3V, TA = +25°C, unless otherwise noted.)
FB = GND, falling edge, 1% hysteresis (typ) 2.85 3.15
1.058 1.17
1.058 1.17
325 675
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
6 _______________________________________________________________________________________
2μs/div
SWITCHING WAVEFORMS
(STEP-DOWN CONVERTER)
3.35V
1.5A
C
A
MAX1864/65 toc07
1A
0
3.30V
A. V
OUT
= 3.3V (PRESET), I
OUT
= 1A, 50mV/div
B. INDUCTOR CURRENT, 500mA/div
C. V
LX
, 10V/div
V
IN
= 12V
10V
0.5A
B
1ms/div
SOFT-START
5V
4V
B
A
MAX1864/65 toc08
2V
0
0
A. V
L
, 5V/div
B. V
OUT
= 3.3V (PRESET), 2V/div
C. INDUCTOR CURRENT, 1A/div
V
IN
= 0 TO 12V
0
1A
C
0
5
10
15
20
25
30
35
40
0246810
POSITIVE LINEAR REGULATOR BASE-
DRIVE CURRENT vs. BASE-DRIVE VOLTAGE
MAX1864/65 toc09
BASE VOLTAGE (V)
BASE-DRIVE SINK CURRENT (mA)
V
FB_
= 1.0V
V
FB_
= 0.96V
REF
B2, B3 AND B4
(MAX1865) ONLY
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN= 12V, V
OUT
= 3.3V, TA = +25°C, unless otherwise noted.)
4.95
4.97
4.99
5.01
5.03
5.05
01.00.5 1.5 2.0 2.5 3.0
OUPUT VOLTAGE vs. LOAD CURRENT
(ADJUSTABLE MODE)
MAX1864/65 toc04
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
4.95
4.97
4.99
5.01
5.03
5.05
0105 15202530
INTERNAL 5V LINEAR REGULATOR
vs. LOAD CURRENT
MAX1864/65 toc05
LOAD CURRENT (mA)
VL (V)
1ms/div
LOAD TRANSIENT
(STEP-DOWN CONVERTER)
3.5V
3.1V
B
A
MAX1864/65 toc06
1A
0
3.3V
A. V
OUT
= 3.3V (PRESET), 200mV/div
B. I
OUT
= 10mA TO 1A, 500mA/div
V
IN
= 12V
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
_______________________________________________________________________________________ 7
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN= 12V, V
OUT
= 3.3V, TA = +25°C, unless otherwise noted.)
2.50
0.01 10.1 100
POSITIVE LINEAR REGULATOR
OUTPUT VOLTAGE vs. LOAD CURRENT
(Q
LDO
= 2N3905)
2.42
2.44
2.46
2.48
MAX18664/65 toc10
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
10 1000
V
SUP(POS)
= 5.0V
V
SUP(POS)
= 3.3V
2.42
2.44
2.46
2.48
2.50
243 5678
POSITIVE LINEAR REGULATOR
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
(Q
LDO
= 2N3905)
MAX1864/65 toc11
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
I
OUT2
= 1mA
I
OUT2
= 100mA
80
70
60
50
40
30
20
10
0
0.1 10 1001 1000
POSITIVE LINEAR REGULATOR
POWER-SUPPLY REJECTION RATIO
(Q
LDO
= 2N3905)
MAX1864/65 toc12
FREQUENCY (kHz)
PSRR (dB)
I
OUT2
= 50mA
POSITIVE LINEAR REGULATOR
LOAD TRANSIENT
(Q
LDO
= 2W3905)
MAX1864/65 toc13
100mA
2.457V
2.467V
A. I
OUTZ
= 1mA TO 100mA, 50mA/div
B. V
OUTZ
= 2.5V, 5mV/div
C
LDO(POS)
= 10μF CERAMIC, V
SUP(POS)
= 3.3V
CIRCUIT OF FIGURE 1
0
B
A
10μs/div
2.50
0.01 0.1 1000100
POSITIVE LINEAR REGUALTOR
OUTPUT VOLTAGE vs. LOAD CURRENT
(Q
LDO
= TIP30)
2.42
2.44
2.46
2.48
MAX1864/65 toc14
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
110
V
SUP(POS)
= 5.0V
V
SUP(POS)
= 3.3V
2.42
2.44
2.46
2.48
2.50
24681012
POSITIVE LINEAR REGULATOR
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
(Q
LDO
= TIP30)
MAX1864/65 toc15
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
I
OUT2
= 1mA
I
OUT2
= 100mA
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
8 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN= 12V, V
OUT
= 3.3V, TA = +25°C, unless otherwise noted.)
-12.00
-12.06
-12.12
-12.18
-12.24
0.01 1
10
1000.1 1000
NEGATIVE LINEAR REGULATOR
OUTPUT VOLTAGE vs. LOAD CURRENT
(Q
LDO
= TIP29)
MAX1864/65 toc19
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
V
SUP(NEG)
= -15V
V
OUT3
= 5V
-12.24
-12.18
-12.12
-12.06
-12.00
-20 -18 -16 -14 -12 -10
NEGATIVE LINEAR REGULATOR
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
(Q
LDO
= TIP29)
MAX1864/65 toc20
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
I
LDO(NEG)
= 100mA
I
LDO(NEG)
= 1mA
80
70
60
50
40
30
20
10
0
0.1 10 1001 1000
POSITIVE LINEAR REGULATOR
POWER-SUPPLY REJECTION RATIO
(Q
LDO
= TIP30)
MAX1864/65 toc16
FREQUENCY (kHz)
PSRR (dB)
I
OUT2
= 150mA
POSITIVE LINEAR REGULATOR
LOAD TRANSIENT
(Q
LDO
= TIP30)
MAX1864/65 toc17
250mA
2.453V
2.473V
A. I
OUT2
= 10mA TO 250mA, 200mA/div
B. V
OUT2
= 2.5V, 10mV/div
C
LDO(POS)
= 10μF CERAMIC, V
SUP(POS)
= 3.3V
CIRCUIT OF FIGURE 1
0
B
A
10μs
0
10
5
25
20
15
40
35
30
45
0426810
NEGATIVE LINEAR REGULATOR BASE-
DRIVE CURRENT vs. BASE-DRIVE VOLTAGE
MAX1864/65 toc18
V
OUT
- VB5 (V)
BASE-DRIVE SOURCE CURRENT (mA)
V
FB5
= 250mV
V
FB5
= 50mV
V
OUT
= 5.0V
V
OUT
= 3.3V
B5 (MAX1865) ONLY
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