Analog Devices ADN8831 prc Datasheet

t

Thermoelectric Cooler (TEC)

Preliminary Technical Data

FEATURES

True current sensing and over current protection
Separate heating and cooling current limits
High efficiency: >90%
Long-term temperature stability: 0.1°C
Temperature lock indication
Temperature monitoring output
Oscillator synchronization with an external signal
Clock phase adjustment for multiple controllers
Programmable switching frequency up to 1MHz
Programmable maximum TEC voltage
Low noise: <0.05% TEC current ripple
TEC current monitoring
Compact 5mm x 5mm LFCSP

APPLICATIONS

Thermoelectric Cooler (TEC) temperature control
Resistive heating element control
Temperature-Stabilization Substrate (TSS) control

Controller

ADN8831

GENERAL DESCRIPTION

The ADN8831 is a monolithic controller that drives a
Thermoelectric Cooler (TEC) to stabilize the temperature of a
laser diode or a passive component used in
telecommunications equipment.

This device relies on a Negative Temperature Coefficient
(NTC) thermistor or a positive temperature coefficient RTD
device to sense the temperature of the object attached to the
TEC. The target temperature is set with an analog input
voltage either from a DAC or with an external resistor divider.

The loop is stabilized by a PID compensation amplifier with
high stability and low noise. The compensation network can
be adjusted by the user to optimize temperature settling time.
The component values for this network can be calculated
based on the thermal transfer function of the laser diode or
obtained from the look-up table given in the applications
notes.

FUNCTIONAL BLOCK DIAGRAM

Thermistor

Inpu

Temp

Set Input

Error

Amplifier

Reference

Compensation

Network

2.5V

PID

Heating

ILim

Limiter

Controls

Cooling

ILim

VLim

MOSFET

Drivers

Oscillator

Freq/Phase

Control

Voltage outputs are provided to monitor both the temperature
of the object and the voltage across the TEC. A 2.5V voltage
reference is provided for the thermistor temperature sensing
bridge.

An external sense resistor provides true current sensing.
Current limits for both heating and cooling can be set
independently.

Rev. PrC

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infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
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Tel: [phone] www.analog.com
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

ADN8831 PRELIMINARY TECHNICAL DATA

TABLE OF CONTENTS

Specifications 3

Theory of Operation 9

Absolute Maximum Ratings 5

Pin Configuration......................................................................... 6

Pin Descriptions ........................................................................... 6

REVISION HISTORY

Revision PrC
7/03—Data Sheet Changed from REV PrB to REV PrC.

Introduction...................................................................................9

Outline Dimensions 10

Ordering Guide 11

Rev. C | Page 2 of 11

PRELIMINARY TECHNICAL DATA ADN8831

SPECIFICATIONS

Table 1. ADN8831—Electrical Characteristics (V+ = 3.0 V to 5.5 V, TA = 25°C, unless otherwise noted.)

Parameter Symbol Conditions Min Typ Max Unit
TEMPERATURE STABILITY
Long Term Stability 10 kΩ thermistor with α = -4.4% at 25C 0.01 °C
PWM OUTPUT DRIVERS

Output Transition Time tR, tF C
Nonoverlapping Clock Delay 50 65 ns
Output Resistance R

Output Voltage Swing SFB V
Output Voltage Ripple ∆SFB f
Output Current Ripple ∆I

LINEAR OUTPUT AMPLIFIER

Output Resistance

Output Voltage Swing LFB 0 VDD V

POWER SUPPLY

Power Supply Voltage

Supply Current

Shutdown Current

Soft-Start Charging Current

Undervoltage Lockout UVLO Low to high threshold 2.5 2.7 V
Standby Current

Standby Threshold

ERROR AMPLIFIERS

Input Offset Voltage

Input Voltage Range V

Common-Mode Rejection Ratio CMRR
Output Voltage Range V

Power Supply Rejection Ratio PSRR

Output Current I
Gain Bandwidth Product GBW

OSCILLATOR

Sync Range f

Oscillator Frequency f

Free-Run Oscillation Frequency f

Phase Adjustment Range

Phase Adjustment Default

REFERENCE VOLTAGE

Reference voltage V

LOGIC OUTPUTS

Logic Low Output Level TEMPGD, SYNCOUT 0.2 V
Logic High Outut Threshold

= 3,300 pF 20 ns

L

O(N1,P1)

f

TEC

IL = 10 mA

= 0 V 0 VDD V

LIM

= 1 MHz 0.2 %

CLK

= 1 MHz 0.2 %

CLK

6 Ω

R

O, LNGATE

R

O, LPGATE

I

OUT

I

OUT

= 2 mA
= 2 mA

85
178

Ω
Ω

V

DD

PWM not switching

I

SY

I

SD

I

SS

I

SB

V

SB

3.0 5.5 V

-40C ≤ TA ≤ +85

SYNCIN/

SD

= 0 V

8

5 µA

12
15

mA
mA

2 µA

SINCIN/

SYNCIN/

SD

= VDD, SS/SB = 0 V

SD

= VDD

1 mA

200 300 mV

V

OS1

V

OS2

0

CM1,2

120 dB

1,2

0

OUT1,2

1,2

-5 +5 mA

OUT1,2

2 MHz

1,2

= 1.5 V, V

V

CM1

V

= 1.5 V, V

CM2

3.0 V ≤ V

DD

IN1P

IN2P

≤ 5.0 V

– V
– V

IN1M

IN2M

10
10

100
100

V

DD

V

DD

µV
µV

V

V

120 dB

CLK

CLK

CLK

SYNCIN/SD connected to external clock

SD

DD

= VDD

DD

, RFREQ = 150kΏ,

,

COMPOSC = V
SYNCIN/

COMPOSC = V

200 1,000 KHz

800 1,000 1,250 kHz

100 1000 KHz

SYNCIN/SD = VDD

Φ

CLK

Φ

CLK

0.1 V ≤ V

PHASE = open 180 °

≤ 2.4 V 25 335 °

PHASE

I

REF

< 2mA 2.37 2.47 2.57 V

REF

V

-

V

DD

0.2V

Rev. C | Page 3 of 11

ADN8831 PRELIMINARY TECHNICAL DATA

Table 2. ADN8831—Electrical Characteristics (V+ = 3.0 V to 5.5 V, TA = 25°C, unless otherwise noted.)

Parameter Symbol Conditions Min Typ Max Unit
TEC CURRENT MEASUREMENT

ITEC Gain A
ITEC Output Range V
ITEC Input Range V
ITEC Bias Voltage V
ITEC Output Current I

TEC VOLTAGE MEASUREMENT

VTEC Gain A
VTEC Output Range V
VTEC Bias Voltage V
VTEC Output Current I

VOLTAGE LIMIT

VLIM Gain A
VLIM Input Range V
VLIM Input Current, cooling I
VLIM Input Current, heating I
VLIM Input Current Accuracy,

heating

CURRENT LIMIT

ILIMC Input Voltage Range V
ILIMH Input Voltage Range V
ILIMC Limit Threshold V
ILIMH Limit Threshold V

TEMPERATURE GOOD

High Threshold V
Low Threshold V

V

V,ITEC

0 VDD V

ITEC

0 VDD V

CS, VLFB

V

ITEC, B

1 mA

OUT,TEC

/(V

ITEC

= VCS = 0 1.2 1.25 1.3 V

LFB

) 98 100 102 V/V

LFB-VCS

V

V,VTEC

0 2.5 V

VTEC

V

VTEC,B

1 mA

VTEC

VTEC

LFB

/(V

= V

) 0.23 0.25 0.27 V/V

LFB-VSFB

= 2.5V 1.2 1.25 1.3 V

SFB

V

V,LIM

0 VDD V

VLIM

V

VLIM,COOL

V

VLIM,HEAT

I

I

VLIM,HEAT

VLIM/IFREQ

5 V/V

SFB/VVLIM

< 1.25V 100 nA

OUT2

>1.25V I

OUT2

mA

FREQ

0.9 1.0 1.1 A/A

1.25 VDD V

ILIMC

0 1.25 V

ILIMH

V

TH,ILIMC

V

TH,ILIMH

= 2.0V 1.98 2.0 2.02 V

ITEC

= 0.5V 0.48 0.5 0.52 V

ITEC

IN2M tied to OUT2, V

OUT1,TH1

IN2M tied to OUT2, V

OUT1,TH2

= 1.5V 1.525 1.530 V

IN2P

= 1.5V 1.470 1.475 V

IN2P

Rev.Pr C | Page 4 of 11