Barrel EM Calorimeter Preamp / Shaper Update

Barrel EM Calorimeter Preamp / Shaper Update

Mitch Newcomer, Andrew Townley

Prepared for Munich Liquid Argon Week 2011

Liquid Argon Week Munich 2011 2

Status April 2011

• Installed IHP’s Cadence IC6 design tools. Some issues identified with PDK but mostly OK.

• A Preamp Design and layout is near completion in IHP’s SG25H3P ( Complementary Bipolar process ).

• Alternative Preamp configurations are being considered for layout.

• Discussion underway with IHP to collaborate on measurements of their PNP devices.


Design Overview & Constraints• Preamp constraints:

– Wide input dynamic range~70nA – 5mA (16 bit)

– Accuracy target 13 bitsPresent fixed input impedance

(25 Ω) across full range– Linear response across input

range– Variable detector

capacitance• 50pF – 1nF

– Able to drive 120 Ω resistance in shaper stage

Cdet Iin

PreampMulti Gain Shaper

Gain Selector

0ns 180ns 360ns 540ns0.0mA

0.6mA

1.1mA I(I1)

Typical input current waveform

X1,10,100


Preamplifier

0ns 180ns 360ns 540ns1.2V

2.8V

4.5V V(out)

0ns 180ns 360ns 540ns1.2V

2.9V

4.5V V(out)

0ns 180ns 360ns 540ns1.2V

2.9V

4.5V V(out)

• Shaping depends on detector capacitance

• Increased Cdet:• Increases tpeak

• Reduces output amplitude.• Increases series noise

• Net: Increased capacitance -> worse SNR

Cdet = 50pF

Cdet = 200pF

Cdet = 1nF

Input current in above: 5mA peak

4


Preamplifier Circuit

Rgain1800

Q2npnH3_HV

RE130

RB1

15

RC1100

RF1

20RF21.246

RSQ150

Q5npnH3_HV

RBQ1

31RE24k

R14k

C11n

D1

D

PULSE(0u ain 50n 12n 400n 1n 1)AC 0

I1 C2

1µ

L2

6n

Rext

10

Noiseless

R51000

C315p

E1

2

Noiseless

R71k

C415p

E2

20

Noiseless

R81k

C515p

C71µ

Q5

Q4

C102p

C112p

Q1npnH3_MV

RSQ2150

Q6

R1110k

Rdrop50 Q3

npnH3_HV

R1010k

Rtrim5600

R30

2

C1210p

VCC1

FBk

VCC2

VEE1

Out

shout

VCC2

VCC2

VCC2

VCC2

VFILT

VCC2

VEE1

VCC2

Out

In

a

Total Preamp Power ~ 45mW

Ideal Shaping elements


Input Stage• Q1: minimize series

noise• Resistor feedback:• Prevent interconnect

parasitics from increasing 1.25Ω.

• Large transient feedback currents ~100mA.

Rgain1800

Q2npnH3_HV

RE130

RB1

15

RC1100

RF1

20RF21.246

R14k

C11n

D1

D


I1

C71µ

C102p

C112p

Q1npnH3_MV

Rdrop50

Q3npnH3_HV

R1010k

Rtrim5600

VCC1

FBk

VEE1

VFILT

VCC2

VEE1

VCC2

In

vgain

a

Input feedback transistor – noise critical!

1mA

VCE = 3.6V

0.7mA

9mA

VCE = 1.5V

VCE = 1.5V

VCC2 = 5V

VCC1 = 2.5V


Input Stage

Rgain1700

Q2npnH3_HV

RE130

RC1100

RF1

20RF21.246

R14k

C11n


I1

C71µ

Q1npnH3_MV

Rdrop50

Q3npnH3_HV

R1010k

Rext

10

VCC1

FBk

VEE1

VFILT

VCC2

VEE1

In

vgain

a

0.0µs 0.2µs 0.4µs 0.6µs 0.8µs 1.0µs0.0mA

2.8mA

5.5mA I(I1) I(Rgain1)0.0µs 0.2µs 0.4µs 0.6µs 0.8µs 1.0µs

0.0V0.8V1.6V2.4V3.2V4.0V4.8V V(vgain) V(vfollow)

vgain

vfollow

I1

I(Rgain1)

0.0µs 0.2µs 0.4µs 0.6µs 0.8µs 1.0µs0.0V

2.0V

3.9V V(cq1,N022) V(vgain,N015)

VCE (Q2)

VCE (Q1)

50pF


Input Stage• Layout considerations:– How to connect to feedback while having minimal

impact on resistance ratio? – Low impedance connection to input pad

RF1

20RF21.246

Q1npnH3_MV

FBk

VCC2

a

2RF1 2RF1

RF2


Feedback resistors• Used lowest per-square

resistance available– Easiest way to achieve 1.25Ω

resistor• Less than one square of

resistance– Tradeoff: ~30Ω feedback

resistor ends up being very large

• Will be some uncertainty in 1.25Ω– Solution: only include 20Ω out

of 30Ω on chip– Externally tunable

• Split 20Ω into two parallel 40Ω– Avoid current crowding effects

600µm

100µm

360µm 60µm


Input StageInput transistor Q1NPN_MV: Nx=8, Ny=1, m=812µm

Emitter connection: L=150µm

TopMetal1

Emitter connection: W=400µm


Feedback resistors• RF1, RF2 set input impedance• Need to dissipate ~100mA peak

– Also must be of same type (for matching)– Width determined by power density allowance

• Max density in Rsheet larger than allowed by contact density• Possible to make addt’l contact row??

RF1

20RF21.246

Q1npnH3_MV

FBk

VCC2

a0.75 µm

(1 cont. per 0.75µm) × (0.4mA per contact) = 0.53mA/µm effective max density

Self Heating

I (mA)

Resis

tanc

e

Safe Area

Output driver• Wide ground, output connections for low

impedance.• Minimize potential for current crowding.

Q5npnH3_HV

RBQ1

31RE24k

Q4

C1210p

I1

1.5mA

VCC2 Out

a

TopMetal1 (Out)2RBQ1

2RBQ1

400µm

TopMetal1 (Out)TopMetal2 (GND)

PNP current mirror

Q4 Q4

Q5 (distributed)

12Liquid Argon Week Munich 2011


Q5npnH3_HV

RBQ1

31RE24k

Q4

C1210p

I1

1.5mA

VCC2 Out

a

Output driver

• Output driver block– PNP “inverts” voltage

signal as current– RC2 converts to voltage– Q5 draws more current

(connected to feedback point)

• Same function PNP or PMOS?– PNP Vceo Limit (2.5V)– PNP Vcbo (4V)

13

Vce = 3.7V

Vce = 3.7V

0.0µs 0.2µs 0.4µs 0.6µs 0.8µs 1.0µs0.0V0.8V1.6V2.4V3.2V4.0V4.8V V(vc_pnp) V(driverin) V(out)

driverIn

vc_pnp

out


Output driver

• PMOS, not PNP?– Higher Vbreakdown. (3.3V)

• Output impedance set by gm of PMOS

– Reduces effective overall gain when driving low-impedance of feedback


Output driver

• PNP:– Output driver gain

0.96

• PMOS:– Output driver gain

0.73. ( First try)


Chip level• Target: Two or

four preamps per chip:

PMOS and PNP?• Add test

structures in extra space.– Look at

breakdown, noise from different transistors.


Summary and Plans

• IHP SG25H3P process is relatively expensive and may offer significant advantages. – PNP Vceo of 2.5V vs operating point of 3.2 to 3.7V is the only

potential issue identified with the process. Transistor is in a safe operating point but the concern is that spontaneous breakdown currents may occur adding to the amplifier noise.

– Plan to submit one or two versions of the preamp in the July 2011 run to understand this issue.

– IHP has expressed interest in working in collaborating on measurements of the radiation sensitivity of the IHP PNP transistors. Details are under discussion.

Barrel EM Calorimeter Preamp / Shaper Update

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