Rainbow Electronics 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 ✕ V

IN

)

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

Pin Configurations

Ordering Information

19-2030; Rev 0; 4/01

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.

PART

MAX1864TEEE -40°C to +85°C 16 QSOP 200

MAX1864UEEE -40°C to +85°C 16 QSOP 100

MAX1865TEEP -40°C to +85°C 20 QSOP 200

MAX1865UEEP -40°C to +85°C 20 QSOP 100

TEMP.

RANGE

PIN­PACKAGE

TOP VIEW

1

POK IN

COMP

2

OUT

3

MAX1864

4

FB

B2

5

FB2

6

B3

7

FB3

8

16

15

VL

14

BST

13

DH

12

LX

DL

11

10

GND

9

ILIM

f

OSC

(kHz)

16 QSOP

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

100 150

0.01 100

100 140

4.46

190 250 310

440 530 620

IN

5.44

MAX1864/MAX1865

xDSL/Cable Modem Triple/Quintuple Output

Power Supplies

_______________________________________________________________________________________ 3

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.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Switching Frequency f

Maximum Duty Cycle D

Soft-Start Period t

Soft-Start Steps V

DH Output Low Voltage I

DH Output High Voltage I

DL Output Low Voltage I

DL Output High Voltage I

DH, DL On-Resistance 310Ω

Output Drive Current Sourcing or sinking, VDH or VDL = VL/2 0.5 A

LX, BST Leakage Current V

POSITIVE ANALOG GAIN BLOCKS

FB2, FB3, FB4 Regulation
Voltage

FB2, FB3, FB4 to B_
Transconductance

Feedback Input Leakage
Current

Driver Sink Current IB_

NEGATIVE ANALOG GAIN BLOCK

FB5 Regulation Voltage

FB5 to B5 Transconductance ∆V

Feedback Input Leakage
Current

Driver Source Current I

POWER GOOD (POK)

OUT Trip Level (Preset Mode) FB = GND, falling edge, 1% hysteresis (typ) 2.88 3 3.12 V

FB Trip Level (Adjustable Mode) Falling edge, 1% hysteresis (typ) 1.070 1.114 1.159 V

FB2, FB3, FB4 Trip Level Falling edge, 1% hysteresis (typ) 1.070 1.114 1.159 V

FB5 Trip Level Rising edge, 35mV hysteresis (typ) 368 500 632 mV

POK Output Low Level I

POK Output High Leakage V

THERMAL PROTECTION (Note 3)

Thermal Shutdown Rising temperature 160 °C
Thermal Shutdown Hysteresis 15 °C

OSC

SOFT

∆V

I

I

MAX

FB

FB5

B5

MAX186_T 160 200 240

MAX186_U 80 100 120

77 82 90 %

1024 1/f

/64 V

REF

= 10mA, measured from DH to LX 0.1 V

SINK

= 10mA, measured from BST to DH 0.1 V

SOURCE

= 10mA, measured from DL to GND 0.1 V

SINK

= 10mA, measured from DL to GND VL - 0.1 V

SOURCE

= VLX = VIN = 28V, VFB = 1.5V 0.03 20 µA

BST

VB2 = VB3 = VB4 = 5V,
I

= IB3 = IB4 = 1mA (sink)

B2

V

= VB3 = VB4 = 5V, IB2 = IB3 = IB4 =

B2

_

FB

0.5mA to 5mA (sink)

_V

FB2

V

FB2

V

FB4

V

B5

= V

FB3

= V

FB3

= 1.188V

= V

OUT

= V

FB4

=

- 2V, V

= 1.5V 0.01 100 nA

VB2 = VB3 = VB4 = 2.5V 10 23

V

= VB3 = VB4 = 4.0V 26

B2

= 3.5V, IB5 = 1mA

OUT

(source)

VB5 = 0, IB5 = 0.5mA to 5mA (source) -13 -20 mV

FB5

V

= -100mV 0.01 100 nA

FB5

V

= 200mV, VB5 = V

FB5

OUT

- 2.0V, V

OUT

3.5V

= 1mA 0.4 V

SINK

= 5V 1 µA

POK

1.226 1.240 1.257 V

-1 -1.75 %

-20 -5 +10 mV

=

10 25 mA

kHz

OSC

mA

MAX1864/MAX1865

xDSL/Cable Modem Triple/Quintuple Output
Power Supplies

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(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

GENERAL

Operating Input Voltage Range
(Note 1)

Quiescent Supply Current I

VL REGULATOR

Output Voltage VL 6V < VIN < 28V, 0.1mA < I

Power-Supply Rejection PSRR VIN = 6V to 28V 3 %

Undervoltage Lockout Trip Level V

DC-DC CONTROLLER

Output Voltage (Preset Mode) V

Feedback Set Voltage
(Adjustable Mode)

Current-Sense Amplifier Voltage
Gain

Current-Limit Threshold
(Internal Mode)

Current-Limit Threshold
(External Mode)

Switching Frequency f

Maximum Duty Cycle D

POSITIVE ANALOG GAIN BLOCKS

FB2, FB3, FB4 Regulation
Voltage

V

IN

VFB = 0, V

IN

UVLO

OUT

V

SET

A

LIM

V

VALLEYVILIM

V

VALLEYVILIM

OSC

MAX

= V
V

VL rising, 3% hysteresis (typ) 3 4 V

FB = GND 3.247 3.380 V

FB = COMP 1.211 1.261 V

VIN - VLX = 250mV 4.12 5.68 V/V

MAX186_T 160 240

MAX186_U 80 120

VB2 = VB3 = VB4 = 5V, IB2 = IB3 = IB4 =
1mA (sink)

FB3

= -0.1V

FB5

= 5V 150 350 mV

= 2.5V 400 660 mV

= V

OUT

FB4

= 4V, V

= 1.5V,

FB2

MAX1864 2

MAX1865 3

<20mA 4.75 5.25 V

LOAD

4.5 28 V

74 90 %

1.215 1.265 V

mA

kHz

FB2, FB3, FB4 to B_
Transconductance

NEGATIVE ANALOG GAIN BLOCK

FB5 Regulation Voltage

FB5 to B5 Transconductance ∆V

∆V

FB

FB5

V

= VB3 = VB4 = 5V, IB2 = IB3 = IB4 =

B2

_

0.5mA to 5mA (sink)

V

= V

OUT

- 2V, V

B5

(source)

VB5 = 0, IB5 = 0.5mA to 5mA (source) -30 mV

= 3.5V, IB5 = 1mA

OUT

-25 +10 mV

-2.25 %

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)

Typical Operating Characteristics

(Circuit of Figure 1, VIN= 12V, V

OUT

= 3.3V, TA = +25°C, unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

POWER GOOD (POK)

OUT Trip Level (Preset Mode) FB = GND, falling edge, 1% hysteresis (typ) 2.85 3.15 V

FB Trip Level
(Adjustable Mode)

FB2, FB3, FB4 Trip Level Falling edge, 1% hysteresis (typ) 1.058 1.17 V

FB5 Trip Level Rising edge, 35mV hysteresis (typ) 325 675 mV

Falling edge, 1% hysteresis (typ) 1.058 1.17 V

EFFICIENCY vs. LOAD CURRENT

(PRESET MODE)

100

VIN = 6.5V

90

80

70

EFFICIENCY (%)

60

50

0.01 1010.1
LOAD CURRENT (A)

EFFICIENCY vs. LOAD CURRENT

(ADJUSTABLE MODE)

100

VIN = 6.5V

90

80

70

EFFICIENCY (%)

60

50

0.01 1010.1
LOAD CURRENT (A)

VIN = 8V

VIN = 12V

VIN = 18V

VIN = 24V

V

= 5.0V

OUT

VIN = 8V

VIN = 12V

VIN = 18V

VIN = 24V

OUTPUT VOLTAGE vs. LOAD CURRENT

(PRESET MODE)

3.33

3.32

MAX1864/65 toc01

3.31

3.30

3.29

OUTPUT VOLTAGE (V)

3.28

V

= 3.3V

OUT

3.27
0 1.0 1.50.5 2.0 2.5 3.0

LOAD CURRENT (A)

MAX1864/65 toc02

MAX1864/65 toc03

MAX1864/MAX1865

xDSL/Cable Modem Triple/Quintuple Output
Power Supplies

6 _______________________________________________________________________________________

E

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

SWITCHING WAVEFORMS

(STEP-DOWN CONVERTER)

3.35V

3.30V

1.5A

1A

0.5A

10V

0

A. V

= 3.3V (PRESET), I

OUT

B. INDUCTOR CURRENT, 500mA/div

, 10V/div

C. V

LX

= 12V

V

IN

2µs/div

OUT

MAX1864/65 toc07

= 1A, 50mV/div

SOFT-START

5V

A

B

C

0

4V

2V

0

1A

0

, 5V/div

A. V

L

= 3.3V (PRESET), 2V/div

B. V

OUT

C. INDUCTOR CURRENT, 1A/div

= 0 TO 12V

V

IN

1ms/div

MAX1864/65 toc08

A

B

C

DRIVE CURRENT vs. BASE-DRIVE VOLTAG

40

V

= 1.0V

35

30

25

20

15

10

BASE-DRIVE SINK CURRENT (mA)

5

0

0246810

FB_

V

= 0.96V

FB_

(MAX1865) ONLY

BASE VOLTAGE (V)

REF

B2, B3 AND B4

MAX1864/65 toc09

POSITIVE LINEAR REGULATOR BASE-

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 10011000

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