UCC3837DTR datasheet, PDF - EEWORLD Datasheet

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UCC3837DTR: DescriptionSPECIALTY ANALOG CIRCUIT, PDSO8, GREEN, PLASTIC, MS-012AA, SOIC-8; CategoryAnalog mixed-signal IC The signal circuit; File Size1MB，14 Pages; ManufacturerRochester Electronics; Websitehttps://www.rocelec.com/; Environmental Compliance

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UCC3837DTR Overview

SPECIALTY ANALOG CIRCUIT, PDSO8, GREEN, PLASTIC, MS-012AA, SOIC-8

UCC3837DTR Parametric

Parameter Name	Attribute value
Is it lead-free?	Lead free
Is it Rohs certified?	conform to
Maker	Rochester Electronics
Parts packaging code	SOIC
package instruction	GREEN, PLASTIC, MS-012AA, SOIC-8
Contacts	8
Reach Compliance Code	unknown
Analog Integrated Circuits - Other Types	ANALOG CIRCUIT
JESD-30 code	R-PDSO-G8
JESD-609 code	e4
length	4.9 mm
Humidity sensitivity level	2
Number of functions	1
Number of terminals	8
Maximum operating temperature	70 °C
Minimum operating temperature
Package body material	PLASTIC/EPOXY
encapsulated code	SOP
Package shape	RECTANGULAR
Package form	SMALL OUTLINE
Peak Reflow Temperature (Celsius)	260
Maximum seat height	1.75 mm
Nominal supply voltage (Vsup)	5 V
surface mount	YES
technology	BICMOS
Temperature level	COMMERCIAL
Terminal surface	NICKEL PALLADIUM GOLD
Terminal form	GULL WING
Terminal pitch	1.27 mm
Terminal location	DUAL
Maximum time at peak reflow temperature	NOT SPECIFIED
width	3.9 mm

UCC3837DTR Preview

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UCC1837

UCC2837

UCC3837

8-Pin N-FET Linear Regulator Controller

FEATURES

•

On Board Charge Pump to Drive

External N-MOSFET

•

Input Voltage as Low as 3V

•

Duty Ratio Mode Over Current

Protection

•

Extremely Low Dropout Voltage

•

Low External Parts Count

•

Output Voltages as Low as 1.5V

DESCRIPTION

The UCC3837 Linear Regulator Controller includes all the features re-

quired for an extremely low dropout linear regulator that uses an external

N-channel MOSFET as the pass transistor. The device can operate from

input voltages as low as 3V and can provide high current levels, thus pro-

viding an efficient linear solution for custom processor voltages, bus ter-

mination voltages, and other logic level voltages below 3V. The on board

charge pump creates a gate drive voltage capable of driving an external

N-MOSFET which is optimal for low dropout voltage and high efficiency.

The wide versatility of this IC allows the user to optimize the setting of

both current limit and output voltage for applications beyond or between

standard 3-terminal linear regulator ranges.

This 8-pin controller IC features a duty ratio current limiting technique that

provides peak transient loading capability while limiting the average

power dissipation of the pass transistor during fault conditions. See the

Application Section for detailed information.

BLOCK DIAGRAM

VDD

CHARGE

PUMP

CURRENT SENSE

AMPLIFIER

140mV

CAP

LEVEL

SHIFT

VOUT

ERROR AMPLIFIER

UVLO

CURRENT SENSE

COMPARATOR

100mV

TIMER

1.5V REF

GND

COMP

UDG-99145

SLUS228A - AUGUST 1999

UCC1837

UCC2837

UCC3837

ABSOLUTE MAXIMUM RATINGS

All pins referenced to GND . . . . . . . . . . . . . . . . . –0.3V to +15V

CS, CT, FB . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to VDD + 0.3V

Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C

Junction Temperature . . . . . . . . . . . . . . . . . . . –55°C to +150°C

Lead Temperature (Soldering, 10sec.) . . . . . . . . . . . . . +300°C

CONNECTION DIAGRAM

DIL-8, SOIC-8 (Top View)

J or N Package, D Package

Currents are positive into, negative out of the specified terminal.

Consult Packaging Section of Databook for thermal limitations

and considerations of packages.

ELECTRICAL CHARACTERISTICS:

Unless otherwise specified, T

= –55°C to 125°C for the UCC1837, –25°C to 85°C

for the UCC2837 and 0°C to 70°C for UCC3837; VDD = 5V, C

= 10nF, C

CAP

= 100nF.

PARAMETER

Input Supply

Supply Current

Under Voltage Lockout

Minimum Voltage to Start

Minimum Voltage After Start

Hysteresis

Reference ( Note 1 )

REF

25°C

0°C to 70°C

–55°C to 125°C

Current Sense

Comparator Offset

Amplifier Offset

Input Bias Current

Current Fault Timer

CT Charge Current

CT Discharge Current

CT Fault Low Threshold

CT Fault Hi Threshold

Fault Duty Cycle

Error Amplifier

Input Bias Current

Open Loop Gain

Transconductance

Charge Current

Discharge Current

–10µA to 10µA

COMP

= 6V

COMP

= 6V

0.5

µA

mMho

µA

= 1V

0.4

1.3

1.2

0.5

1.5

3.3

1.9

0.6

1.7

µA

= 5V

0°C to 70°C

–55°C to 125°C

120

100

140

0.5

110

115

160

µA

1.485

1.470

1.455

1.5

1.515

1.530

1.545

2.00

1.6

0.25

2.65

2.2

0.45

3.00

2.6

0.65

VDD = 5V

VDD = 10V

1.2

1.5

TEST CONDITIONS

MIN

TYP

MAX UNITS

UCC1837

UCC2837

UCC3837

ELECTRICAL CHARACTERISTICS:

Unless otherwise specified, T

= –55°C to 125°C for the UCC1837, –25°C to 85°C

for the UCC2837 and 0°C to 70°C for UCC3837; VDD = 5V, C

= 10nF, C

CAP

= 100nF.

PARAMETER

FET Driver

Peak Output Current

Average Output Current

Max Output Voltage

CAP

= 10V, VOUT = 1V

VOUT = 1V

VDD = 4.5V, I

OUT

= 0µA

VDD = 4.5V, I

OUT

= 10µA, 0°C to 70°C

VDD = 4.5V, I

OUT

= 10µA, –55°C to 125°C

Charge Pump

CAP Voltage

VDD = 4.5V, C/S = 0V

VDD = 12V, C/S = 0V

12.5

16.5

0.5

8.4

7.5

1.5

100

9.7

2.5

175

µA

TEST CONDITIONS

MIN

TYP

MAX UNITS

Note 1: This is defined as the voltage on FB which results in a DC voltage of 8V on VOUT.

PIN DESCRIPTIONS

CAP:

The output of the charge pump circuit. A capacitor

is connected between this pin and GND to provide a

floating bias voltage for an N-Channel MOSFET gate

drive. A minimum of a 0.01µF ceramic capacitor is rec-

ommended. CAP can be directly connected to an exter-

nal regulated source such as +12V, in which case the

external voltage will be the source for driving the

N-Channel MOSFET.

COMP:

The output of the transconductance error ampli-

fier and current sense amplifier. Used for compensating

the small signal characteristics of the voltage loop (and

current loop when Current Sense Amplifier is active in

over curret mode).

CS:

The negative current sense input signal. This pin

should be connected through a low noise path to the low

side of the current sense resistor.

CT:

The input to the duty cycle timer circuit. A capacitor

is connected from this pin to GND, setting the maximum

ON time of the over current protection circuits. See the

Application Section for programming instructions.

FB:

The inverting terminal of the voltage error amplifier,

used to feedback the output voltage for comparison with

the internal reference voltage. The nominal DC operating

voltage at this pin is 1.5V

GND:

Ground reference for the device. For accurate out-

put voltage regulation, GND should be referenced to the

output load ground.

VDD:

The system input voltage is connected to this

point. VDD must be above 3V. VDD also acts as one

side of the Current Sense Amplifier and Comparator.

VOUT:

This pin directly drives the gate of the external

N-MOSFET pass element. The typical output impedance

of this pin is 6.5kΩ.

APPLICATION INFORMATION

Topology and General Operation

Unitrode Application Note U-152 is a detailed design of a

low dropout linear regulator using an N-channel

MOSFET as a pass element, and should be used as a

guide for understanding the operation of the circuit

shown in Fig. 1.

Charge Pump Operation

The internal charge pump of the UCC3837 is designed to

create a voltage equal to 3 times the input VDD voltage

at the CAP pin. There is an internal 5V clamp at the input

of the charge pump however that insures the voltage at

CAP does not exceed the ratings of the IC. This CAP

voltage is used to provide gate drive current to the exter-

nal pass element as well as bias current to internal sec-

tions of the UCC3837 itself. The charge pump output has

a typical impedance of 80kΩ and therefore the loading of

the IC and the external gate drive reduces the voltage

from its ideal level. The UCC3837 can operate in several

states including having the error amplifier disabled (shut

down), in normal linear regulation mode, and in overdrive

mode where the linear regulator is responding to a tran-

sient load or line condition. The maximum output voltage

available at VOUT is shown in Fig. 2 for these various

modes of operation.

The charge pump output is designed to supply 10µA of

average current to the load which is typically the

MOSFET gate capacitance present at the VOUT pin.The

capacitor value used at CAP is chosen to provide holdup

UCC1837

UCC2837

UCC3837

APPLICATION INFORMATION

0.020

OVERDRIVE

LINEAR REGULATOR

E/A DISABLED

330µF

UCC3837

VDD

VOUT

IRL2203N

OR EQUIVALENT

3.3V

1.8k

1.5k

1000µF

VOUT

ON/OFF

0.1µF

CAP

0.1µF

COMP

10k

COMP

820pF

COMP

GND

VDD

Figure 2. Typical V

OUT(max)

vs. VDD.

UDG-99137

Figure 1. Typical application 5V to 3.3V, 5A

of the CAP voltage should the external load exceed the

average current, which occurs during load and line tran-

sient conditions. The value of CAP also determines the

startup time of the linear regulator. The voltage at CAP

charges up with a time constant determined by the

charge pump output impedance (typically 80kΩ) and the

value of the capacitor on CAP.

An external voltage such as +12V may be tied to the

CAP pin directly to insure a higher value of VOUT, which

may be useful when a standard level MOSFET is used or

when VDD is very low and the resulting VOUT voltage

may need to be higher. With an external source applied

to CAP, the maximum voltage at VOUT will be approxi-

mately 1V below the external source.The external +12V

source should be decoupled to GND using a minimum of

a 0.01µF capacitor.

Choosing a Pass Element

The UCC3837 is designed for use with an N-channel

MOSFET pass element only. The designer may choose

a logic level or standard gate level MOSFET depending

on the input voltage, the required gate drive, and the

available voltage at VOUT as discussed previously.

MOSFET selection should be based on required dropout

voltage and gate drive characteristics. A lower R

DS(on)

MOSFET is used when low dropout is required, but this

type of MOSFET will have higher gate capacitance which

may result in a slower transient response.

A MOSFET used in linear regulation is typically operated

at a gate voltage between the threshold voltage and the

gate plateau voltage in order to maintain high gain. This

mode of operation is linear, and therefore the channel re-

sistance is higher than the manufacturer’s published

DS(on)

value. The MOSFET should only be operated in

the non-linear (switch) mode under transient conditions,

when minimum dropout voltage is required.

Disabling the UCC3837

Grounding the CAP pin will remove the drive voltage and

effectively disable the output voltage. The device used to

short the output of CAP should have a very low leakage

current when in the OPEN state, since even a few

microamps will lower the charge pump voltage.

A second method of disabling the UCC3837 is to place a

short circuit across C

COMP

. This will have an advantage

of a quicker restart time as the voltage at CAP will not be

completely discharged. The charge pump will be loaded

down by the typical 40µA charging current of the error

amplifier with this configuration, resulting in a lower volt-

age at CAP.

Compensating the Error Amplifier

Using a MOSFET as an external pass element intro-

duces a pole in the control loop that is a function of the

UCC3837 output impedance, R

OUT

, typically 6.5kΩ, and

the MOSFET input gate capacitance. Fig. 3 indicates

that in the normal operation of a linear regulator using a

MOSFET, the gate capacitance can be predicted directly

from the MOSFET characteristic charge curve, using the

relationship:

∆

Qgth

∆

Vgth

This pole can be canceled by programming a zero fre-

quency on the output of the UCC3837 error amplifier

equal to the pole frequency. Therefore:

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UCC3837DTR Related Products

	UCC3837DTR	UCC2837D	UCC2837DTR	UCC2837N	UCC3837D	UCC2837DG4	UCC3837DG4
Description	SPECIALTY ANALOG CIRCUIT, PDSO8, GREEN, PLASTIC, MS-012AA, SOIC-8	SPECIALTY ANALOG CIRCUIT, PDSO8, GREEN, PLASTIC, MS-012AA, SOIC-8	SPECIALTY ANALOG CIRCUIT, PDSO8, GREEN, PLASTIC, MS-012AA, SOIC-8	SPECIALTY ANALOG CIRCUIT, PDIP8, GREEN, PLASTIC, DIP-8	SPECIALTY ANALOG CIRCUIT, PDSO8, GREEN, PLASTIC, MS-012AA, SOIC-8	SPECIALTY ANALOG CIRCUIT, PDSO8, GREEN, PLASTIC, MS-012AA, SOIC-8	SPECIALTY ANALOG CIRCUIT, PDSO8, GREEN, PLASTIC, MS-012AA, SOIC-8
Is it lead-free?	Lead free	Lead free	Lead free	Lead free	Lead free	Lead free	Lead free
Is it Rohs certified?	conform to	conform to	conform to	conform to	conform to	conform to	conform to
Maker	Rochester Electronics	Rochester Electronics	Rochester Electronics	Rochester Electronics	Rochester Electronics	Rochester Electronics	Rochester Electronics
Parts packaging code	SOIC	SOIC	SOIC	DIP	SOIC	SOIC	SOIC
package instruction	GREEN, PLASTIC, MS-012AA, SOIC-8	GREEN, PLASTIC, MS-012AA, SOIC-8	GREEN, PLASTIC, MS-012AA, SOIC-8	GREEN, PLASTIC, DIP-8	GREEN, PLASTIC, MS-012AA, SOIC-8	GREEN, PLASTIC, MS-012AA, SOIC-8	GREEN, PLASTIC, MS-012AA, SOIC-8
Contacts	8	8	8	8	8	8	8
Reach Compliance Code	unknown	unknown	unknown	unknown	unknown	unknow	unknow
Analog Integrated Circuits - Other Types	ANALOG CIRCUIT	ANALOG CIRCUIT	ANALOG CIRCUIT	ANALOG CIRCUIT	ANALOG CIRCUIT	ANALOG CIRCUIT	ANALOG CIRCUIT
JESD-30 code	R-PDSO-G8	R-PDSO-G8	R-PDSO-G8	R-PDIP-T8	R-PDSO-G8	R-PDSO-G8	R-PDSO-G8
JESD-609 code	e4	e4	e4	e4	e4	e4	e4
length	4.9 mm	4.9 mm	4.9 mm	9.81 mm	4.9 mm	4.9 mm	4.9 mm
Humidity sensitivity level	2	2	2	NOT SPECIFIED	2	2	2
Number of functions	1	1	1	1	1	1	1
Number of terminals	8	8	8	8	8	8	8
Maximum operating temperature	70 °C	85 °C	85 °C	85 °C	70 °C	85 °C	70 °C
Minimum operating temperature	-	-25 °C	-25 °C	-25 °C	-	-25 °C	-
Package body material	PLASTIC/EPOXY	PLASTIC/EPOXY	PLASTIC/EPOXY	PLASTIC/EPOXY	PLASTIC/EPOXY	PLASTIC/EPOXY	PLASTIC/EPOXY
encapsulated code	SOP	SOP	SOP	DIP	SOP	SOP	SOP
Package shape	RECTANGULAR	RECTANGULAR	RECTANGULAR	RECTANGULAR	RECTANGULAR	RECTANGULAR	RECTANGULAR
Package form	SMALL OUTLINE	SMALL OUTLINE	SMALL OUTLINE	IN-LINE	SMALL OUTLINE	SMALL OUTLINE	SMALL OUTLINE
Peak Reflow Temperature (Celsius)	260	260	260	NOT SPECIFIED	260	260	260
Maximum seat height	1.75 mm	1.75 mm	1.75 mm	5.08 mm	1.75 mm	1.75 mm	1.75 mm
Nominal supply voltage (Vsup)	5 V	5 V	5 V	5 V	5 V	5 V	5 V
surface mount	YES	YES	YES	NO	YES	YES	YES
Temperature level	COMMERCIAL	OTHER	OTHER	OTHER	COMMERCIAL	OTHER	COMMERCIAL
Terminal surface	NICKEL PALLADIUM GOLD	NICKEL PALLADIUM GOLD	NICKEL PALLADIUM GOLD	NICKEL PALLADIUM GOLD	NICKEL PALLADIUM GOLD	NICKEL PALLADIUM GOLD	NICKEL PALLADIUM GOLD
Terminal form	GULL WING	GULL WING	GULL WING	THROUGH-HOLE	GULL WING	GULL WING	GULL WING
Terminal pitch	1.27 mm	1.27 mm	1.27 mm	2.54 mm	1.27 mm	1.27 mm	1.27 mm
Terminal location	DUAL	DUAL	DUAL	DUAL	DUAL	DUAL	DUAL
Maximum time at peak reflow temperature	NOT SPECIFIED	NOT SPECIFIED	NOT SPECIFIED	NOT SPECIFIED	NOT SPECIFIED	NOT SPECIFIED	NOT SPECIFIED
width	3.9 mm	3.9 mm	3.9 mm	7.62 mm	3.9 mm	3.9 mm	3.9 mm
technology	BICMOS	BICMOS	BICMOS	BICMOS	BICMOS	-	BICMOS

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