Caravel Analog User

This is the first test chip from the Chipalooza challenge 2024. 11 designs made it on the April tapeout.

The projects on this tapeout and their source URLs are as follows:

1.  	High-speed crystal oscillator (4-16MHz)
	hsxo-cpz1 
	https://github.com/efabless/sky130_ht_ip__hsxo_cpz1 (forked)
	https://github.com/htfab/hsxo-cpz1
	Tamas Hubai

2.  	Brownout detector
	sky130_ajc_ip__brownout
	https://github.com/efabless/sky130_ajc_ip__brownout (forked)
	https://github.com/ajcci/sky130_ajc_ip__brownout
	Robin Tsang

3.  	Overvoltage detector
	sky130_ajc_ip__overvoltage
	https://github.com/efabless/sky130_ajc_ip__overvoltage (forked)
	https://github.com/ajcci/sky130_ajc_ip__overvoltage
	Robin Tsang

4.  	Power-on-Reset
	sky130_ajc_ip__por
	https://github.com/efabless/sky130_ajc_ip__por (forked)
	https://github.com/ajcci/sky130_ajc_ip__por
	Robin Tsang

5.  	Comparator
	sky130_ak_ip__comparator
	https://github.com/efabless/sky130_ak_ip__comparator (forked)
	https://github.com/andrewkkang/sky130_ak_ip__comparator
	Andrew Kang

6.  	Low-speed crystal oscillator (32kHz)
	sky130_be_ip__lsxo
	https://github.com/efabless/sky130_be_ip__lsxo (forked)
	https://github.com/b-etz/sky130_be_ip__lsxo
	Brady Etz

7.  	Temperature sensor
	sky130_od_ip__tempsensor
	https://github.com/efabless/sky130_od_ip__tempsensor (forked)
	https://github.com/ordicker/sky130_od_ip__tempsensor
	Or Dicker

8.  	Low power operational amplifier
	sky130_rodovalho_ip__lpopamp
	https://github.com/efabless/sky130_rodovalho_ip__lpopamp (forked)
	https://github.com/lhrodovalho/sky130_rodovalho_ip__lpopamp
	Luis Henrique Rodovalho

9.  	High gain-bandwidth operational amplifier
	sky130_td_ip__opamp_hp
	https://github.com/efabless/sky130_td_ip__opamp_hp (forked)
	https://github.com/tdextrous/sky130_td_ip__opamp_hp
	Thomas Dexter

10. 	Overvoltage detector
	sky130_vbl_ip__overvoltage
	https://github.com/efabless/sky130_vbl_ip__overvoltage (forked)
	https://github.com/LDFranck/sky130_vbl_ip__overvoltage
	Lucas Franck, William Orlato, and Toni Tejada

11.	Bandgap (not from Chipalooza)
	bandgap
	https://github.com/efabless/sky130_cw_ip (forked)
	https://github.com/christoph-weiser/mpw7
	Christoph Weiser

12.	Power FET (not from Chipalooza)
	power_stage
	(in this repository)
	Weston Braun

13.	Bias current generator (not from Chipalooza)
	bias_generator
	(in this repository)
	Tim Edwards

14.	Ground-isolated analog switch (not from Chipalooza)
	isolated_switch_ena1v8
	(in this repository)
	Tim Edwards

(Documentation, including test instructions, still needs to be completed)

:---: | :---

Building:

Get the dependencies above by doing "make get_ip_blocks" in the top level directory. This will clone all of the IP blocks from various github repository sources into the "dependencies" directory.

The test chip is generated in magic by running magic in the mag/ directory and issuing the command "source construct_testchip.tcl".

Verifying:

In the top level directory, do "make run-precheck". This requires at least setting environment variables PDK_ROOT, PDK, and PRECHECK_ROOT. If the PDK is installed with open_pdks, then PRECHECK_ROOT can be set to open_pdks/sources/precheck_sky130.

Testing:

All projects are connected either to the logic analyzer (128 I/O bits) or the GPIO pins. Generally speaking, static control bits (enable and trim, for example) are logic analyzer outputs. Dynamic digital bits are routed to GPIO digital outputs, while analog I/O are routed to the analog connections of the GPIO.

Each power supply is routed through gated power pFETs so each project can be powered individually. Each power supply connection internally is routed to a bare analog pin for monitoring the supply voltage of the project. Be aware that these are ESD-sensitive points!

Power supplies are enabled through a differential switch. Due to time constraints, the differential signals (enable, !enable) were both routed to the logic analyzer. Both bits need to be set correctly.

Most projects take current biases which are distributed by a central bias current generator circuit. Various test point bias currents are connected through ground-isolated switches to GPIO analog signals.

Project circuit blocks are described below, starting at the top left corner of the chip and working counterclockwise around the chip perimeter.

High Gain-Bandwidth Operational Amplifier
(Thomas Dexter)
Enable: la_data_out[37]
Bias: 100nA when selected
Selection: la_data_out[40] = 0
Upstream analog power supply: vdda2/vssa2
Upstream digital power supply: vccd2/vssd2
Power supply monitor: io_analog[10]
Power supply enable: la_data_out[60]
Power supply !enable: la_data_out[61]
Amp output: gpio_noesd[7]
Amp negative input: gpio_analog[8] when selected
Selection: la_data_out[36] = 1
Amp positive input: gpio_analog[9] when selected
Selection: la_data_out[34] = 1

Temperature sensor
(Or Dicker)
Enable: la_data_out[35]
Bias: gpio_noesd[2] (nominally 1.2V) when selected
Selection: la_data_out[122] = 1
Upstream digital power supply: vccd2/vssd2
Power supply monitor: io_analog[9]
Power supply enable: la_data_out[58]
Power supply !enable: la_data_out[59]
Vbe1_out: gpio_analog[8] when selected
Selection: la_data_out[36] = 0
Vbe2_out: gpio_analog[9] when selected
Selection: la_data_out[34] = 0

Comparator
(Andrew Kang)
Enable: la_data_out[28]
Hysteresis: la_data_out[29:30]
Trim: la_data_out[25:27],la_data_out[33:31]
Bias: 400nA when selected
Selection: la_data_out[44] = 0
Upstream analog power supply: vdda2/vssa2
Upstream digital power supply: vccd2/vssd2
Power supply monitor: io_analog[8]
Power supply enable: la_data_out[56]
Power supply !enable: la_data_out[57]
Comparator output: io_out[17]
Comparator negative input: gpio_analog[12] when selected
Selection: la_data_out[22] = 1
Comparator positive input: gpio_analog[11] when selected
Selection: la_data_out[23] = 1

Low power operational amplifier
(Luis Henrique Rodovalho)
Enable: la_data_out[21]
Bias: 10uA when selected
Selection: la_data_out[46] = 0
Upstream analog power supply: vdda2/vssa2
Upstream digital power supply: vccd2/vssd2
Power supply monitor: io_analog[7]
Power supply enable: la_data_out[54]
Power supply !enable: la_data_out[55]
Amplifier output: gpio_analog[13]
Amplifier negative input: gpio_analog[11] when selected
Selection: la_data_out[23] = 0
Amplifier positive input: gpio_analog[12] when selected
Selection: la_data_out[22] = 0

High speed crystal oscillator
(Tamas Hubai)
Enable: la_data_out[19]
Standby: la_data_out[20]
Bias: 10uA when selected
Selection: la_data_out[47] = 0
Upstream analog power supply: vdda2/vssa2
Upstream digital power supply: vccd2/vssd2
Power supply monitor: io_analog[6]
Power supply enable: la_data_out[52]
Power supply !enable: la_data_out[53]
Oscillator out: io_out[23]
Crystal Xin: gpio_analog[14]
Crystal Xout: gpio_analog[15]

Bandgap (Christoph Weiser)
Enable: none (enable via power supply)
Bias: self-biased
Trim: la_data_out[9,8,10,7,11,6,12,5,13,4,14,3,15,2,16,1]
Upstream digital power supply: vccd2/vssd2
Power supply monitor: io_analog[5]
Power supply enable: la_data_out[50]
Power supply !enable: la_data_out[51]
Bandgap output: gpio_analog[16] when selected
Selection: la_data_out[18] = 1

Brownout detector (Robin Tsang)
Enable: la_data_out[109]
Bias: gpio_noesd[2] (nominally 1.2V) when selected
Selection: la_data_out[122] = 0
Bias: 200nA when selected
Selection: la_data_out[43] = 0
Trip point select (otrip): la_data_out[112:113,111]
Trip point select (vtrip): la_data_out[107:106,108]
Force enable RC osc: la_data_out[115]
Force disable RC osc: la_data_out[114]
Force short oneshot: la_data_out[116]
Current source select: la_data_out[110]
Upstream analog power supply: vdda1/vssa1
Upstream digital power supply: vccd1/vssd1
Power supply monitor: io_analog[0]
Power supply enable: la_data_out[77]
Power supply !enable: la_data_out[76]
Outb: io_out[0]
Dcomp: io_out[1]
Vunder: io_out[5]
Timed out: la_data_in[116]

Overvoltage detector (Robin Tsang)
Enable: la_data_out[100]
Bias: gpio_noesd[2] (nominally 1.2V) when selected
Selection: la_data_out[122] = 0
Bias: 200nA when selected
Selection: la_data_out[42] = 0
Trip point select (otrip): la_data_out[105:102]
Current source select: la_data_out[101]
Upstream analog power supply: vdda1/vssa1
Upstream digital power supply: vccd1/vssd1
Power supply monitor: io_analog[1]
Power supply enable: la_data_out[75]
Power supply !enable: la_data_out[74]
Ovout: io_out[6]

Power-on-reset (Robin Tsang)
Bias: gpio_noesd[2] (nominally 1.2V) when selected
Selection: la_data_out[122] = 0
Bias: 200nA when selected
Selection: la_data_out[41] = 0
Trip point select (otrip): la_data_out[96:98]
Force PDN: la_data_out[94]
Force enable RC osc: la_data_out[93]
Force disable RC osc: la_data_out[92]
Force short oneshot: la_data_out[99]
Current source select: la_data_out[95]
Upstream analog power supply: vdda1/vssa1
Upstream digital power supply: vccd1/vssd1
Power supply monitor: io_analog[2]
Power supply enable: la_data_out[73]
Power supply !enable: la_data_out[72]
POR: io_out[7]
PORb: io_out[9]
Osc_clk: io_out[3]
Dcomp: io_out[2]
Pwup_filt: io_out[4]
Startup timed out: la_data_in[120]
POR timed out: la_data_io[119]

Low-speed (32kHz) crystal oscillator (Brady Etz)
Enable: la_data_out[86]
Standby: la_data_out[85]
Bias: 50nA when selected
Selection: la_data_out[39] = 0
Upstream analog power supply: vdda1/vssa1
Upstream digital power supply: vccd1/vssd1
Power supply monitor: io_analog[3]
Power supply enable: la_data_out[69]
Power supply !enable: la_data_out[68]
Dout: io_out[12]
Crystal XIn: gpio_noesd[3]
Crystal XOut: gpio_noesd[4]

Overvoltage detector (Lucas Franck & William Orlato)
Enable: la_data_out[91]
Bias: gpio_noesd[2] (nominally 1.2V) when selected
Selection: la_data_out[122] = 1
Trip point select (vtrip): la_data_out[87:90]
Upstream analog power supply: vdda1/vssa1
Upstream digital power supply: vccd1/vssd1
Power supply monitor: io_analog[4]
Power supply enable: la_data_out[65]
Power supply !enable: la_data_out[64]
OVout: io_out[13]

Three power FETs are unused but should be kept disabled:
Enable: la_data_out[62], la_data_out[67], la_data_out[71]
Disable: la_data_out[63], la_data_out[66], la_data_out[70]

These current sources/sinks are multiplexed to analog pins not otherwise being used for projects:

100nA source (test0): gpio_analog[16] when selected
Selection: la_data_out[18] = 0

100nA source (test1): gpio_analog[10] when selected
Selection: la_data_out[17] = 1

100nA sink (test1): gpio_analog[6] when selected
Selection: la_data_out[124] = 1

3.7uA sink (snk_3700): gpio_analog[5] when selected
Selection: la_data_out[123] = 1

100nA sink (test0): gpio_analog[0] when selected
Selection: la_data_out[118] = 1

Refer to README for this sample project documentation.