Datasheet

ManualsBrandsANALOG DEVICES ManualsLinear ICsLinear IC - In-amp InAmp WLCSP 11 (1.57x2.04)

40 μA Micropower Instrumentation

Amplifier in WLCSP Package

AD8235

Rev. 0

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FEATURES

Low power

40 A maximum supply current

6 nA shutdown current

Low input currents

50 pA input bias current

25 pA input offset current

High Common Mode Rejection Ratio (CMRR)

110 dB CMRR , G = 100

Space saving

WLCSP package

Zero input crossover distortion

Versatile

Rail-to-rail input and output

Shutdown

Gain set with single resistor (G = 5 to 200)

AD8236: µSOIC package version of AD8235

APPLICATIONS

Medical instrumentation

Low-side current sense

Portable electronics

GENERAL DESCRIPTION

The AD8235 is the smallest and lowest power instrumentation

amplifier in the industry. It is available in a 1.5 mm × 2.2 mm

wafer level chip scale package (WLCSP). The AD8235 draws

a maximum quiescent current of 40 µA. In addition, it draws a

maximum 500 nA of current during shutdown mode, making

it an excellent instrumentation amplifier for battery powered,

portable applications.

The AD8235 can operate on supply voltages as low as 1.8 V. The

input stage allows for wide rail-to-rail input voltage range without

the crossover distortion, common in other designs. The rail-to-

rail output enables easy interfacing to ADCs.

The AD8235 is an excellent choice for signal conditioning. Its

low input bias current of 50 pA and high CMRR of 110 dB

(G = 100) offer tremendous value for its size and low power.

It is specified over the extended industrial temperature range of

−40°C to 125°C.

CONNECTION DIAGRAM

RGRG

REF

–IN

+IN

OUT

210k 210k52.5k 52.5k

AD8235

–V

B3 A1 D1

ESD

PROTECTION

ESD

PROTECTION

A3 D3

SDN

ESD

PROTECTION

ESD

PROTECTION

ESD

PROTECTION

OP AMP

ESD

PROTECTION

8211-001

TOP VIEW

(BALL SIDE DOWN)

Not to Scale

Figure 1.

PIN CONFIGURATION

BALL A1

INDICATOR

–V

OUT

SDN

–IN

REF

NC = NO CONNECT

+IN

08211-004

Figure 2. 11-Ball WLCSP (CB-11-1)

1.0

2.0

4.0

3.0

0.5

1.5

3.5

2.5

OUTPUT VOLTAGE (V)

INPUT COMMON-MODE VOLTAGE

5.0

4.5

(V)

5.55.00.5–0.5 1.5 2.0 3.0 4.0 4.50 1.0 2.5 3.5

G = 5

= 5V

REF

= 2.5V

G = 5

= 1.8V

REF

= 0.9V

8211-002

Figure 3. Wide Common-Mode Voltage Range vs. Output Voltage

Summary of content (20 pages)

PAGE 1
40 μA Micropower Instrumentation Amplifier in WLCSP Package AD8235 FEATURES CONNECTION DIAGRAM ESD PROTECTION ESD PROTECTION ESD PROTECTION 210kΩ 52.5kΩ 52.5kΩ –VS A1 D1 210kΩ OP AMP A NC B2 NC D2 ESD PROTECTION OP AMP B ESD PROTECTION ESD PROTECTION A3 D3 B1 VOUT 08211-001 AD8235 +IN –IN Figure 1.
PAGE 2
AD8235 TABLE OF CONTENTS Features .............................................................................................. 1 Shutdown Feature....................................................................... 15 Applications ....................................................................................... 1 Layout Recommendations ........................................................ 15 General Description .........................................................................
PAGE 3
AD8235 SPECIFICATIONS +VS = 5 V, −VS = 0 V (GND), VREF = 2.5 V, TA = 25°C, G = 5, RLOAD = 100 kΩ to GND, SDN pin tied to +VS, unless otherwise noted. Table 1. Parameter COMMON-MODE REJECTION RATIO (CMRR) CMRR DC G=5 G = 10 G = 100 G = 200 NOISE Voltage Noise Spectral Density, RTI RTI, 0.1 Hz to 10 Hz G=5 G = 200 Current Noise VOLTAGE OFFSET Input Offset, VOS Average Temperature Coefficient (TC) Offset RTI vs.
PAGE 4
AD8235 Parameter GAIN Gain Range Gain Error G=5 G = 10 G = 100 G = 200 Nonlinearity G=5 G = 10 G = 100 G = 200 Gain vs. Temperature G=5 G > 10 INPUT Differential Impedance Common-Mode Impedance Input Voltage Range OUTPUT Output Voltage High, VOH Output Voltage Low, VOL Short-Circuit Limit, ISC REFERENCE INPUT RIN IIN Voltage Range Gain to Output SHUTDOWN OPERATION Shutdown current Test Conditions Min G = 5 + 420 kΩ/RG VS = ±2.5 V, VREF = 0 V, VOUT = −2 V to +2 V 5 Typ Max Unit 200 1 V/V 0.005 0.
PAGE 5
AD8235 +VS = 1.8 V, −VS = 0 V (GND), VREF = 0.9 V, TA = 25°C, G = 5, RLOAD = 100 kΩ to GND, SDN pin tied to +VS, unless otherwise noted. Table 2. Parameter COMMON-MODE REJECTION RATIO (CMRR) CMRR DC G=5 G = 10 G = 100 G = 200 NOISE Voltage Noise Spectral Density, RTI RTI, 0.1 Hz to 10 Hz G=5 G = 200 Current Noise VOLTAGE OFFSET Input Offset, VOS Average Temperature Coefficient (TC) Offset RTI vs.
PAGE 6
AD8235 Parameter GAIN Gain Range Gain Error G=5 G = 10 G = 100 G = 200 Nonlinearity G=5 G = 10 G = 100 G = 200 Gain vs. Temperature G=5 G > 10 INPUT Differential Impedance Common-Mode Impedance Input Voltage Range OUTPUT Output Voltage High, VOH Output Voltage Low, VOL Short-Circuit Limit, ISC REFERENCE INPUT RIN IIN Voltage Range Gain to Output SHUTDOWN OPERATION Shutdown Current Test Conditions Min G = 5 + 420 kΩ/RG VS = ±0.9 V, VREF = 0 V, VOUT = −0.6 V to +0.6 V 5 1 Max Unit 200 1 V/V 0.
PAGE 7
AD8235 ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Table 3. Parameter Supply Voltage Output Short-Circuit Current Input Voltage (Common Mode) Differential Input Voltage Storage Temperature Range Operating Temperature Range Junction Temperature ESD Human Body Model Charge Device Model Machine Model Rating 6V 55 mA ±VS ±VS −65°C to +125°C −40°C to +125°C 125°C θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages.
PAGE 8
AD8235 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS BALL A1 INDICATOR 1 2 3 +VS SDN –IN VOUT NC RG A B REF RG –VS NC +IN D 08211-004 C TOP VIEW (BALL SIDE DOWN) Not to Scale NC = NO CONNECT Figure 4. Pin Configuration (Top View Looking Through Package) Table 5. Pin Function Descriptions Pin No. A1 B1 C1 D1 A2 B2, D2 A3 B3, C3 D3 Mnemonic +VS VOUT REF −VS SDN NC −IN RG +IN Description Positive Power Supply Terminal. Output Terminal. Reference Voltage Terminal.
PAGE 9
AD8235 TYPICAL PERFORMANCE CHARACTERISTICS G = 5, +VS = 5 V, VREF = 2.5 V, RL = 100 kΩ tied to GND, TA = 25°C, SDN pin connected to +VS, unless otherwise noted 2400 GAIN = 5 NUMBER OF UNITS 2100 1800 1500 1200 900 0 –40 08211-105 300 –30 –20 –10 0 10 CMRR (µV/V) 20 5µV/DIV 1s/DIV 08211-008 600 40 30 Figure 8. 0.1 Hz to 10 Hz RTI Voltage Noise Figure 5.
PAGE 10
AD8235 120 10 GAIN = 100 100 GAIN = 200 CMRR (µV/V) PSRR (dB) 5 GAIN = 10 80 GAIN = 5 60 0 40 –5 1 10 100 1k 10k 100k FREQUENCY (Hz) –10 –40 Figure 11. Negative PSRR vs. Frequency, RTI, VS = ±0.9 V, ±2.5 V, VREF = 0 V 50 100 120 GAIN = 100 30 60 GAIN (dB) GAIN = 200 GAIN = 100 40 GAIN = 10 20 10 GAIN = 5 0 –10 GAIN = 10 –20 20 –30 GAIN = 5 10 100 1k 10k 100k FREQUENCY (Hz) –40 08211-012 1 10 1k 10k 100k 1M FREQUENCY (Hz) Figure 12. CMRR vs.
PAGE 11
AD8235 RLOAD = 100kΩ TIED TO GND RLOAD = 10kΩ TIED TO GND 1.5 2.0 2.5 3.0 OUTPUT VOLTAGE (V) 3.5 4.0 4.5 3.5 3.0 2.5 2.0 1.5 1.0 0 –0.5 08211-017 1.0 (4.98V, 4.737V) (0.01V, 4.24V) 4.0 (4.98V, 0.767V) (0.01V, 0.27V) 0.5 VS = 5V 0.5 4.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 OUTPUT VOLTAGE (V) 08211-020 INPUT COMMON-MODE VOLTAGE (V) NONLINEARITY (5ppm/DIV) 5.0 Figure 20. Input Common-Mode Voltage Range vs. Output Voltage, G = 5, VS = 5 V, VREF = 2.5 V Figure 17.
PAGE 12
AD8235 1.8 INPUT COMMON-MODE VOLTAGE (V) 1.6 (1.75V, 1.705V) (0.03V, 1.533V) 1.4 1.2 2V/DIV 1.0 0.8 444μs TO 0.01% 0.6 0.4 (1.75V, 0.275V) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 OUTPUT VOLTAGE (V) 1ms/DIV Figure 23. Input Common-Mode Voltage Range vs. Output Voltage, G = 200, VS = 1.8 V, VREF = 0.9 V 08211-026 0 –0.2 08211-023 (0.03V, 0.103V) 0.2 Figure 26. Large Signal Pulse Response and Settling Time, VS = ±2.5 V, VREF = 0 V, RLOAD = 10 kΩ to VREF +VS –0.002 –0.
PAGE 13
AD8235 500 20mV/DIV SETTLING TIME (µs) 400 300 200 0 1 0 2 3 08211-032 100µs/DIV 08211-029 100 4 OUTPUT VOLTAGE STEP SIZE (V) Figure 32. Settling Time vs. Output Voltage Step Size, VS = ±2.5 V, VREF = 0 V, RLOAD = 10 kΩ Tied to VREF Figure 29. Small Signal Pulse Response, G = 5, CL = 100 pF, VS = ±0.9 V, VREF = 0 V, RLOAD = 100 kΩ to VREF 40 38 20mV/DIV SUPPLY CURRENT (µA) 36 1.8V 34 32 30 5V 28 26 24 20 –40 Figure 30. Small Signal Pulse Response, G = 200, CL = 100 pF, VS = 2.
PAGE 14
AD8235 THEORY OF OPERATION B3 RG ESD PROTECTION REF C1 ESD PROTECTION 210kΩ RG C3 +VS –VS A1 D1 ESD PROTECTION 52.5kΩ A2 SDN B1 VOUT 210kΩ OP AMP A NC B2 NC D2 52.5kΩ RG ESD PROTECTION OP AMP B ESD PROTECTION ESD PROTECTION A3 D3 –IN +IN 08211-034 AD8235 Figure 35. Simplified Schematic BASIC OPERATION The AD8235 amplifies the difference between its positive input (+IN) and its negative input (−IN). The REF pin allows the user to level-shift the output signal.
PAGE 15
AD8235 SHUTDOWN FEATURE The AD8235 includes a shutdown pin (SDN) that further enhances the flexibility and ease of use in portable applications where power consumption is critical. A logic level signal can be applied to this pin to switch to shutdown mode, even when the supply is still on. When connecting the SDN pin to +VS or applying a voltage within +VS − 0.5 V, the AD8235 operates in its normal condition and, therefore, draws approximately 40 μA of supply current.
PAGE 16
AD8235 INCORRECT Board Thickness Typical board thicknesses used in the industry range from 0.4 mm to 1.6 mm and are most applicable for the AD8235. The thickness selected depends on the required robustness of the populated system assembly. The thinner board results in smaller shear stress range, creep shear strain range, and creep strain energy density range in the solder joints under the thermal loading. Therefore, the thinner build-up board leads to longer thermal fatigue life of solder joints [John H.
PAGE 17
AD8235 +VS +VS AD8235 AD8235 REF REF –VS –VS TRANSFORMER TRANSFORMER +VS +VS C C 1 fHIGH-PASS = 2πRC AD8235 R AD8235 REF REF R –VS AC-COUPLED 08211-038 –VS AC-COUPLED Figure 40. Creating an IBIAS Path INPUT BIAS CURRENT RETURN PATH RF INTERFERENCE The AD8235 input bias current is extremely small at less than 50 pA. Nonetheless, the input bias current must have a return path to common.
PAGE 18
AD8235 To eliminate high frequency common-mode signals while using smaller source resistors, a low-pass RC network can be placed at the input of the instrumentation amplifier (see Figure 42). The filter limits the input signal bandwidth according to the following relationship: FilterFreq DIFF = FilterFreq CM = 1 2πR(2 C D + C C + C G ) COMMON-MODE INPUT VOLTAGE RANGE The common-mode input voltage range is a function of the input voltages, reference voltage, supplies, and the output of Internal Op Amp A.
PAGE 19
AD8235 APPLICATIONS INFORMATION AC-COUPLED INSTRUMENTATION AMPLIFIER LOW POWER HEART RATE MONITOR An integrator can be tied to the AD8235 in feedback to create a high-pass filter, as shown in Figure 43. This circuit can be used to reject dc voltages and offsets. At low frequencies, the impedance of the capacitor, C, is high. Therefore, the gain of the integrator is high. DC voltage at the output of the AD8235 is inverted and gained by the integrator.
PAGE 20
AD8235 OUTLINE DIMENSIONS 0.657 0.602 0.546 1.61 1.57 1.53 0.020 REF SEATING PLANE 0.348 0.328 0.308 3 2 1 A BALL A1 IDENTIFIER 2.08 2.04 2.00 0.330 0.310 0.290 1.50 REF B 0.50 REF C D 0.355 0.330 0.304 0.04 MAX COPLANARITY BOTTOM VIEW (BALL SIDE UP) 1.00 REF 0.280 0.250 0.220 060409-A TOP VIEW (BALL SIDE DOWN) 0.230 0.212 0.192 Figure 45.